Browsing by Author "Girija, T"
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ThesisItem Open Access Enhancing morpho-physiological vigour of sesame seedlings for improving productivity and weed competitiveness(Department of Plant Physiology, College of Horticulture, Vellanikkara, 2017) Sreepriya, S; KAU; Girija, TSesame is one of the oldest oilseed crops grown in summer rice fallows of Kerala. Weed infestation is a major biotic stress affecting the yield of sesame. Seedling growth of sesame is slow during the first four weeks, making it a poor competitor during this period. Weed suppression during the early stages of crop establishment (10 to 30 DAS) is important for improving the productivity of the crop. The present study was initiated to enhance the early vigour of sesame plants by suitable seed priming treatments and also to assess the effect of early vigour on weed competitiveness and analyse the carry over effect of these treatments on the productivity of the crop. The variation in varietal response to these priming treatments were also studied. A laboratory study was conducted with five popular varieties of sesame viz., Surya, Thilak, Kayamkulam 1, Thilarani and Thilathara, released from Kerala Agricultural University. Ten priming treatments with plant growth regulators (IAA, GA), micronutrients (MnSO4, borax), mixture of MnSO4 and borax with GA (Tank mix), biofertilizers (phosphobacteria, azospirillum, PGPR mix-1) and water were tried. Results on observations showed that seed priming improved the germination and vigour of all the five varieties tested. Among the treatments, priming with micronutrients and hormones gave the best results. Based on the vigour index, five priming treatments were selected for the field trial and the variety Thilak, which gave maximum response to these treatments, was used as the test variety in the field. The experiment was laid out in split plot design at ORARS, Kayamkulam. Weeded and unweeded treatments formed the main plots and five selected treatments along with control (unprimed seeds) were the sub-plot treatments. Observations on morphological characters were studied at 20 days interval and yield characters were recorded at the time of harvest. Physiological and biochemical effects of the priming treatments were studied at vegetative and reproductive stages of the crop. Weed count and weed dry matter were recorded at 10 DAS and at the time of harvest in the unweeded plots. Weed control efficiency of the priming treatments was computed at the time of harvest. The biochemical parameters such as contents of chlorophyll, total soluble protein and GA were higher during the reproductive phase as compared to the vegetative phase. Chlorophyll including chlorophyll a and chlorophyll b, and soluble protein content showed greatest improvement in MnSO4 primed plants. The nitrate reductase enzyme plays a major role in nitrogen metabolism of the plant. In the present study, the nitrate reductase enzyme activity was found to be higher during the reproductive phase of the crop in all the treatments except for control (unprimed seeds) and water priming. The IAA content was also higher in the reproductive phase in all the treatments. Major improvement in IAA content was observed with borax priming. The growth indices such as crop growth rate, relative growth rate, net assimilation rate and leaf area index were improved with priming treatments in both unweeded and weeded plots. Yield and yield attributes such as number of branches, number of capsules and seeds per capsule improved significantly with MnSO4 and tank mix treatments, which contributed to higher yield. The improvement in vigour of sesame plants with seed priming treatments reduced the weed count and weed dry matter production in the unweeded plots as compared to the control (unprimed seeds) due to the higher competitiveness of the primed seeds. The study revealed that seed priming with MnSO4 or Tank mix of GA, borax and MnSO4 can be an effective component in the integrated management of weeds in sesame as it can contribute to 30 per cent control of weed growth.ThesisItem Open Access Growth and physiology of isachne miliacea roth. in different soil types and its sensitivity to common herbicides(Department of plant physiology, College of horticulture, Vellanikkara, 2015) Suada, A P; KAU; Girija, TIsachne miliacea Roth. is one of the predominant weed in the low land rice fields of Kerala. The weed belongs to the family poaceae. Locally it is known as ‘Chovverippullu, Naringa, Njammal, Changalipullu.’ Previous studies conducted in Kerala Agricultural University showed that I. miliacea alone can contribute to 61 per cent reduction in the production of rice in Onattukara region. Presently, the weed is reported to be spreading to other rice growing regions of Kerala. It is found both during the Rabi and Kharif seasons. Eradication of the weed is very difficult, as it is propagated through seeds and stem cuttings. Hence a study was proposed to understand the growth and propagation of I. mliacea in different rice growing soils and also to understand the response of the weed to common herbicides popular in the state. The effect of different soil types on growth and phenology of I. miliacea was studied in pot culture with soil collected from five different rice growing regions viz. Onattukara, Kole, Kuttanad, Pokkali and Palakkad. Ten kg soil each was filled in plastic boxes of size 50 x 25 cm and five replications was maintained for each soil type. Ten seeds were sown in each box and the germination was noted. At two leaf stage when the seedlings were identifiable, a single seedling was retained in each box and the excess seedlings were removed, irrigated regularly and the different phenophases and the morphological attributes were observed at 15 days interval. The study showed that soil type had a profound influence on the phenology and growth pattern of the weed. Due to high acidity (pH -3.6) and salinity (EC – 4.46 dS/m) seeds sown in Pokkali soils did not germinate. Plants grown in Kuttanad soil showed earlier germination, tillering, flowering, seed formation and seed maturation, while those from Palakkad soil required more number of days to reach these phenophases. The variation in morphological attributes such as total shoot length, leaf number, internodal length, number of panicles and seeds produced per plant were significant. Plants grown in Palakkad soil had higher total shoot length and internodal length as compared to Kuttanad soil, but the leaf number, number of panicles per plant and number of seeds produced per panicle were higher in Kuttanad soil, where the potassium, phosphorus and organic content was higher compared to other soils. As the nutrient status of Onattukara and Kole land soils were similar (potassium, phosphorus, magnesium, zinc, manganese and sulphur), the performance of the weed in those two soil types were also on par for many of the morphological characters. Propagation of I. miliacea was affected by ambient temperature, shade, depth of burial and moisture level of soil. The seeds germinated when the temperature range was between 15 - 400C, the highest germination was obtained at 250C. Growth of the weed was highest in open condition compared to shaded condition. Under 50 per cent shade, seed germination declined by 70 per cent. Higher germination per cent of weed was obtained under moist condition, while stem cuttings performed well in both moist and submerged condition. The germination per cent of the weed, reduced with depth of burial. Sensitivity of the weed to pre emergence herbicides was tested using seed bioassay technique. In the first set, herbicide soaked filter paper was placed at the bottom of petri plates and seeds were placed on it (TP method). In the second set, the herbicide soaked filter paper was placed on top of the seeds and another water soaked filter paper was placed at the bottom (BP method I). In the third set, seeds were placed in between two filter paper soaked with herbicides (BP method II). BP method II gave the best result for all the pre emergence herbicides. However, oxyfluorfen and butachlor showed higher weed suppression in all the methods tried. Sensitivity of the weed to post emergence herbicides was tested using whole plant bioassay technique. Here, the weed was grown in mud pots and the herbicides were sprayed when the weed was in the vegetative phase. Among post emergence herbicides tested, best control was obtained for azimsulfuron followed by cyhalofop butyl and fenoxaprop p- ethyl. The weed was susceptible to these chemicals. In the case of bispyribac sodium and penoxsulam though initial control was observed, regrowth was seen after two weeks and so the chemical was classified as moderately resistant to the weed. The weed was resistant to pyrazosulfuron, where no drying symptoms were observed. All the four non-traditional rice herbicides tested viz., glyphosate, diuron, paraquat and glufosinate ammonium gave excellent control of I. miliacea and no regrowth was observed after two weeksArticleItem Open Access Hydration-dehydration technique, a mid-storage correction to prolong viability of rice seeds(Kerala Agricultural University, 1996) Girija, T; Sukumara Dev, V P; Asha Sankar, M; Rajappan Nair, N; KAUThesisItem Open Access Impact of seed deterioration on seedling vigour in mango (Mangifera indica L.)(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2002) Anila, P; KAU; Girija, TThe present study on 'Impact of seed deterioration on seedling vigour in mango' was undertaken at the Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara during 1999-2001 with the objectives of assessing the variability of seedling characters obtained fr0111 a single plant, the effect of seed deterioration on seedling characters and to ascertain the critical moisture content of the varieties. Three varieties of mango were selected for the study. Assessment of variability of seedling characters of these varieties revealed that seedling girth is the most variable character, variability within varieties and between varieties was high for this character. Moreover, the response of girth to variation in seed weight due to loss in moisture content of the seed was also high indicating that this character may be influenced by both genetic factor as well as the physiological condition of the seed. The critical, moisture content was estimated to be 24% for Chandrakkaran, 30% for Moovandan and 28% for Puliyan. Seedling characters like height, girth, internodal length, number of leaves etc. were studied. These characters were found to be highly depended upon the moisture content of seed. There was considerable reduction in these characters with loss of moisture from seed. Polyembryonic nature of these varieties were not affected by seed desiccation. Biochemical characters like chlorophyll content, phenol content and sugar content were found to decrease with seed desiccation. Electrolyte leakage was found to be high with seed desiccation leading to reduction in viability. Seedling vigour was found to be positively correlated with biochemical characters.ThesisItem Open Access Interactive effect of UV radiation and elevated temperature on rice growth and physiology(Department of Plant Physiology, College of Horticulture, Vellanikkara, 2018) Amjath, T; KAU; Girija, TRice is a staple food for more than half the world’s population. The growth and productivity of the crop is intimately associated with climatic variants. Among different climatic factors, temperature and incidence of UV-B radiation are important. The incidence of stress (Temperature and UV) at different stages of growth determines the productivity of the crop. Hence the present study was undertaken with the prime objective of evaluating the interactive effect of UV-B radiation and elevated temperature at different phenophases of Uma rice variety and its effect on growth and productivity. The study was carried out at College of Horticulture, Vellanikkara during Jan to May- 2018. The UV-B radiation and atmospheric temperature were maximum during this season. 14 days old Uma seedlings were used as plantingmaterial. It was grown under four different conditions, namely T1(10C lesser than ambient+ low UV-B), T2 (10 C higher than ambient+ low UV-B), T3 (20 C higher than ambient+ low UV-B), T4 (Open condition). The plants were kept in the polyhouses for 30 days during three phenophases of the crop viz, seedling to active tillering (P1), active tillering to early reproductive (P2) and early reproductive to harvest (P2) and returned to ambient condition to complete their life cycle. Morphological, biochemical, physiological and yield parameters were analyzed during the growth period. Exposure of plants to T1 (10 C below ambient) had least negative influence on growth, physiology and yield of the crop across different developmental stages. A 10C increase in temperature above ambient (T2) in phase 1 improved the yield and yield parameter. However the impact was negative under same condition during phase 2 (P2) and phase 3 (P3). Maximum deleterious effects were observed in T3 during phase 2 and 3. Plants grown in open condition had lower plant height and higher number of tillers as compared to plants grown in polyhouse condition (T1, T2 and T3). Number of days to heading was less in plants grown under high temperature conditions (T2 and T3). The photosynthetic rate, stomatal conductance and transpiration rate were maximum in T2 condition in all the three phases of growth. Analysis of biochemical parameters showed that the IAA content was 67 percent lesser in plants grown under open condition as compared to ployhouses during P1. Similar decrease was also found in the case of gibberellic acid and chlorophyll. Amylose content of the grain were significantly reduced in the plants grown under T2 and T3 conditions during P2 and P3. Plants exposed to temperature above ambient level (T2 and T3) during P2 and P3 stages recorded a reduction in yield. Maximum yield reduction was observed in T3 condition which was 13 percent in P2 and 56 percent in P3. Reduction in spikelets number and pollen viability were the main reasons. The study indicates that plants were most sensitive to high temperature stress during the P2 and P3 stages, which can contribute to drastic yield decline while, the early stress can have a positive influence on yield.ThesisItem Open Access Mitigating the phytotoxic effect of ALS inhibiting herbicides in rice (Oryza sativa L.)(College of Horticulture, Vellanikkara, 2016) Nithya, N; KAU; Girija, TThe study on “Mitigating the phytotoxic effect of ALS inhibiting herbicides in rice (Oryza sativa L.).” was conducted during 2015-2016 at Agricultural research station, Mannuthy, with the prime objective of mitigating the growth inhibition due to the application of post emergent ALS (Aceto Lactate Synthase) inhibitors, bispyribac sodium azimsulfuron and to improve the productivity of rice. The experiment was laid out in RBD with three replications and there were eleven treatments comprising of two Aceto Lactate Synthase inhibitors viz., bispyribac sodium (30 g ai/ha) , azimsulfiiron (35g ai/ha) and five mitigating treatments viz., Urea spray (0.1%), Micronutrient spray (1 gm each of zinc sulphate and borax, 0.01 gm of molybdic acid/litre), NAA spray (100ppm), Tank mix and water spray (1000 ml) with hand weeded as control. Herbicides were sprayed on 15 DAS whereas mitigating treatments were sprayed on 35 DAS. Observations on morphological, physiological, biochemical, yield and yield attributes of rice were recorded. Morphological characters were studied at 15 days interval and biochemical estimations were done 7 days after herbicide application and at the time of flowering. Mitigation treatments resulted in a 10- 13 % increase in height and 4-8 % improvement in tiller number of rice plant at harvest compared to plants in the hand weeded plot. Effect of mitigating treatments on growth attributes viz., relative growth rate, crop growth rate , net assimilation rate, and leaf area index indicated that at the final stages of growth there was no significant difference between the treatments. However during the critical stages of growth i.e.,45-75 DAS significant variation was observed. Among the mitigation treatments, bispyribac sodium followed by tank mix applied plots had higher values as compared to the other treatments whereas azimsulfuron applied plots had the lowest value for these parameters. The biochemical parameters such as nitrate reductase enzyme activity and total soluble protein content showed an initial decline when estimated one week after application of herbicide. At the time of flowering, recovery was higher in the plants where foliar spray of mitigating treatments were given as compared to water spray. Tank mix applied plots recorded more value for the above biochemical parameters in both bispyribac sodium and azimsulfuron applied plots. Proline content and catalase enzyme activity showed increase with herbicide application when compared to hand weeded control indicating that application of these chemicals may be imparting stress to the plant, however by flowering time in most of the treatments there was recovery. The physiological parameters such as chlorophyll content, and IAA content showed decline but there was no significant variation in photosynthetic rate and stomatal conductance between treatments when estimated one week after herbicide application. In the case of chlorophyll content the recovery of the plant was comparatively less as compared to all other chemical constituents. Treatments in azimsufuron applied plots showed maximum reduction in these constituents. In the present study, among the ALS inhibiting herbicides azimsulfuron contributed to higher inhibition in growth and yield of rice when compared with bispyribac sodium. Mitigating treatments contributed to 20 to 24 % increase in grain yield and 20 to 27 % increase in straw yield of rice. Tank mix applied plots recorded highest grain yield and urea applied plots recorded highest straw yield.ThesisItem Open Access Morpho-physiological changes in rice due to application of selected post emergent herbicides(Department of Plant Physiology, College of Horticulture, Vellanikara, 2014) Ramanarayana, C V; KAU; Girija, TThe study on “Morpho-physiological changes in rice due to application of selected post emergent herbicides” was conducted during 2013-2014 at Alappad kole lands in farmer’s field. The objective of the experiment was to study the morphological, physiological and biochemical changes in rice due to application of Acetyl CoA carboxylase and Acetolactate synthase enzyme inhibitors and their effect on growth and yield of rice. The experiment was laid out in RBD with four replications and there were seven treatments comprising of three Acetyl CoA carboxylase enzyme inhibitors viz., Cyhalofop butyl, Fenoxaprop -p- ethyl and Metamifop and three Acetolactate synthase enzyme inhibitors viz., Bispyribac sodium, Azimsulfuron and Almix with Hand weeded as control. Herbicides were sprayed on 15 DAS. Observations on morphological, physiological, biochemical, yield attributes and yield of rice were recorded. Biochemical estimations were done on 7 days after herbicide application and at the time of flowering. Morphological characters were studied at 15 days interval. Herbicide application resulted in a two to four percent reduction in height and one to six percent reduction in tiller number of rice plant at harvest as compared to plants in the Hand weeded plot. Effect of herbicides on growth attributes viz., RGR, CGR and NAR indicated that at the initial and final stages of growth there was no significant difference between the treatments. However during the critical stages of growth i.e., 45-75 DAS significant variation was seen. Among the herbicide treatments, Bispyribac sodium.followed by Cyhalofob butyl applied plots had higher values as compared to the other herbicides. Azimsulfuron applied plots had the lowest value for these parameters. Among the growth indices LAI showed significant reduction irrespective of the herbicide throughout the growth stages as compared to Hand weeded control. The biochemical parameters such as nitrate reductase enzyme activity, phenol content, total soluble protein content and total amino acid content showed an initial decline when estimated one week after application of herbicide but by the time of flowering all the herbicide treated plants showed recovery. However the recovery was higher for Bispyribac sodium in the ALS inhibiting group and Cyhalofop in the ACCase inhibiting group. Proline content and catalase enzyme activity showed increase with herbicide application as compared to Hand weeded control indicating that application of these chemicals may be imparting stress to the plant, however by flowering time in most of the treatments there was recovery. Among the treatments, plants in the Almix and Azimsulfuron applied plots showed less recovery. The physiological parameters such as chlorophyll content, photosynthetic rate, stomatal conductance and IAA content showed decline when estimated one week after herbicide application. . In the case of chlorophyll content the recovery of the plant was comparatively less as compared to all other chemical constituents. Azimsufuron and Almix application contributed to maximum reduction in these constituents. Weed count and weed dry weight was taken on 60 DAS. The lowest values were recorded in Bispyribac sodium treatment. Azimsulfuron also a broad spectrum herbicide, was found less effective in the present study compared to Bispyribac sodium. In the present study, 5 to 17 percent reduction in grain yield and 6 to 17 percent reduction in straw yield of rice was observed by herbicide application. Among the ALS enzyme inhibitors, the lowest reduction in grain and straw yield was observed in Bispyribac sodium treatment and maximum reduction was in Azimsulfuron treatment. Among the ACCase enzyme inhibitors, Cyhalofop butyl showed least reduction in grain and straw yield of rice while fenoxaprop showed maximum reduction.ThesisItem Open Access Physiological and molecular studies on genera of loranthaceae and their management(Department of Plant Physiology, College of Agriculture, Vellanikkara, 2021) Garggi, C; KAU; Girija, THemiparasitic plants belonging to the family Loranthaceae are major tree parasites. Dendrophthoe falcata, Helicanthus elastica, Macrosolen capitellatus are major hemiparasites infecting perennial crops of the tropics. Helixanthera wallichiana and Taxillus tomentosus are two important hemiparasites infecting the fruit and timber trees of the high ranges. Apart from being a troublesome parasite they also serve as a linchpin reservoir supporting an extensive ecosystem. The prevailing investigation namely “Physiological and molecular studies on genera of Loranthaceae and their management” was carried out at Department of Plant Physiology, College of Agriculture, Vellanikkara, Thrissur, during the period from 2015 to 2020. Morphological characters of representative species viz., Dendrophthoe falcata, Helicanthus elastica, Macrosolen capitellatus, Helixanthera wallichiana and Taxillus tomentosus from five selected. Samples of these were collected from various locations from the plains and highranges of Thrissur. In all the selected species, leaves were oppositely arranged, D. falcata and H. elastica had oblong shaped leaves, leaves of M. capitellatus was lanceolate in shape, and H. wallichiana and T. tomentosus had narrow ovate shaped leaves. Fruit was berry in all the genera. Hemiparasites possess a physiological structure called haustoria through which they abstract water and minerals from the host. Haustorial branching pattern in all the genera was found to be basal epicortical root (ber). Haustorial portions of the collected samples were treated and prepared to permanent slides. Anatomical sections of the haustoria of the five selected genera of Loranthaceae revealed that there exists a transition zone between the host- parasite interphase region. This was observed as undifferentiated parenchymatous cells which aid in translocation of molecules. Presence of xylem elements were observed at the haustorial region. Haustorial anatomy of M. capitellatus was unique as there was complete merging of cells of host and parasite at the interphase region. The lineage of five selected genera belonging to Loranthaceae family were studied by molecular assay. The results from the ISSR assay revealed that, T. tomentosus and M. capitellatus had maximum similarity compared to all the other genera, since it formed a separate cluster. Morphological characterization indicated similarity between the two genera in the haustorial attachment pattern. Both the species have a single point of attachment to the host. H. wallichiana was observed to be more similar to the first cluster. D. falcata formed another branch close to H. wallichiana, where all these four genera formed the main group. H. elastica formed a separate lone group, which indicated genetical variance from other genera studied. Morphological observations supporting such a uniqueness in this parasite was noted in haustorial branching type, where basal epicortical root with lateral tendril like structures from nodes and internodes were observed. The parasite also showed other phylogenetically advanced characters according to Angiosperm Phylogeny Group (APG system) of classification like fused corolla and calyx. To study the host parasite interaction, root feeding studies with labelled 32P were undertaken. Cocoa plants infected with both parasites D. falcata and H. elastica was selected for the study. 32P in carrier solution of 1000ppm orthophosphoric acid @ 2 mCi per plant was fed to the surface running roots of cocoa. Leaf samples of the host and parasite were collected at 7 and 14 days after treatment and assayed for radio activity. To understand the translocation from parasite to host, leaves of the parasitic species both D. falcate and H. elastica were also smeared with labelled 32P and leaf samples were analysed from different parts of both the host and the parasite. These experiments were done on different trees. Leaf samples of the host and parasite were collected at 2, 7 and 14 DAT and assayed for radio activity. Results from the radio assay indicated that there is bidirectional movement of nutrients from host to parasite and parasite to host. There exists a prioritized partitioning pattern for nutrient transport (phosphorous) based on demand by the sink, regardless of the parent plant. The host and parasite were found to act as a single system indicating their coexistence. Physiological parameters of the host and parasites were also observed using InfraRed Gas Analyser (IRGA) for a period of six months. It was observed that stomatal conductivity of D. falcata and H. elastica was significantly higher than the host cocoa. Even though there was no much variation in the photosynthetically active radiation (PAR) received by the host and parasite during the period of observation, D. falcata and H. elastica had significantly higher rate of photosynthesis than cocoa. Transpiration rate of both parasites were significantly higher than their host. Carboxylation efficiency and light use efficiency of H. elastica were observed to be significantly higher than the host, cocoa. Field experiment was conducted to improve the management strategy and control the spread of the parasite. Use of surfactant was found to improve the efficacy of ethephon in controlling the regrowth of parasite on host plant. Non- ionic surfactants viz., Nonyl phenol ethoxylate (NPE) and Organosilicone (OS) were selected for the study. A combination of OS (0.5 ml/L) surfactant with ethephon (25ml/L) was successful in suppressing the regrowth of both D. falcata and H. elastica.ThesisItem Open Access Physiological evaluation of herbicidal effects on rice, broadleaved weeds and sedges(Department of Plant Physiology, College of Horticulture, Vellanikkara, 2019) Linu, C; KAU; Girija, TThe study on “Physiological evaluation of herbicidal effects on rice, broadleaved weeds and sedges” was conducted during the period from July 2018 to November 2018 at Agricultural Research Station, Mannuthy, Thrissur. The objectives of the study were identification of broadleaved weeds and sedges that are selectively controlled by Almix®, penoxsulam and 2,4-D and also to evaluate the effect of these herbicides on the growth, physiology and yield of rice. The experiment was laid out in RBD with three replications and six herbicidal treatments. The rice variety selected for the study was Jyothi. Treatments included normal and twice the normal doses of 2,4-D, Almix® and penoxsulam and two controls (hand weeded and unweeded). The herbicides were sprayed 20 DAS. Morphological parameters were observed at 20 days interval. Biochemical parameters were estimated before herbicidal application, one week after herbicidal application and at the time of flowering. Yield attributes and yield were recorded during the harvest of the crop. Twice the normal doses of herbicides resulted in 10-12% reduction in plant height of rice while normal doses of herbicides resulted in 3-6% reduction in plant height at the time of harvest. Tiller number of rice crop was found to be affected by herbicide application.At the time of harvest, tiller number of 2,4-D (normal dose) applied plot was on par with hand weeded plot while in case of Almix® and penoxsulam the reduction was 4 and 5 % respectively. Twice the normal doses of herbicides adversely affected tiller number in all three herbicide treatments and it was significantly lower than unweeded control. Number of days taken for flowering was found to be affected by herbicide application compared to hand weeded control. Effect of herbicides on growth indices viz., crop growth rate (CGR) and net assimilation rate (NAR) indicated that only after critical period of growth, there was a significant variation among the treatments. In case of relative growth rate (RGR) and leaf area index (LAI) there was a significant reduction in herbicide applied plots compared to hand weeded control throughout the growth stages. Twice the normal doses of herbicides showed greater reduction in the growth attributes. Biochemical parameters such as soluble protein, total amino acid and nitrate reductase enzyme activity showed a decline in herbicide treatments compared to hand weeded control. Proline content and catalase enzyme activity showed an increase with herbicide application while physiological parameters such as IAA content, cholorophyll content, stomatal conductance and net photosynthesis showed a decline. Twice the normal doses of herbicides significantly affected these parameters compared to the recommended doses of these chemicals. Weed count, dry weight, weed control efficiency and weed persistence index were taken one week after herbicide application and at 60 DAS. Lower weed count, dry weight, weed persistence index and higher weed control efficiency were recorded in twice the normal doses of herbicides as compared to the normal doses. In the present study, grain yield was highest in handweeded plot which was on par with normal doses of 2,4-D and Almix®. Since disease infestation was higher in penoxsulam treatment the yield was also affected. Twice the normal doses of herbicides contributed to 22-33% reduction in grain and 19-23% reduction in straw yield respectively. Among the herbicides 2,4-D (synthetic auxin type) showed a better performance compared to Almix® and penoxsulam (ALS inhibiting type). A net house experiment was conducted to understand the bioefficacy of the herbicides on broadleaved weeds and sedges, viz. Marsilea quadrifoliata, Ludwigia parviflora, Cyperus iria, Fimbristylis miliacea and Sphenoclea zeylanica. The study revealed that Marsilea quadrifoliata was not controlled by both the doses of 2,4-D and penoxsulam while both the doses of Almix® could effectively control the weed. Ludwigia parviflora was controlled by both the doses of 2,4-D while only twice the normal dose of Almix® could control the weed. Penoxsulam did not have any effect on the weed. Fimbristylis miliacea was controlled by penoxsulam and 2,4-D but Almix® was not effective for this weed. Cyperus iria could be controlled only by 2,4-D while Sphenoclea zeylanica was effectively controlled by all the three herbicide formulations. The dosage of chemical influenced the time taken for complete drying of the plant. Though catalase and superoxide dismutase enzyme activity showed increase in the resistant weeds, further studies are required to elucidate the resistance mechanism.ThesisItem Open Access Physiological intervention for mitigating temperature stress in rice(Department of Plant Physiology, College of Horticulture , Kerala Agricultural University, Vellanikkara, 2020) Femina, K; KAU; Girija, TRice is an important cereal crop which is most widely consumed as staple food by millions of people. Demand for rice is projected to increase across globe with rapid increase in population. Rice being a tropical crop requires a fairly high temperature for optimum growth and development. However, temperatures above 35 0C cause heat injuries in rice including changes in morphological, physiological and yield characters. Hence, the present study was conducted to identify ameliorative chemicals to mitigate high temperature stress, which is a common occurrence in the third crop season where temperatures can go up to 40 0C in the reproductive stage leading to yield loss. Popular rice varieties, Uma and Manuratna, which are also suitable for the third crop season were chosen for the study. The whole study was divided in to two experiments. The first experiment was carried out in glass house at College of Horticulture, Vellanikkara during January to May, 2019. Ten day old rice seedlings of Uma (V1) and Manuratna (V2) were planted in pots. Treatments included five ameliorative sprays viz. Ascorbic acid (T1), Glutathione (T2), Melatonin (T3), Salicylic acid (T4) and Hoagland solution (T5) along with Water sprayed (T6) and Unsprayed (T7) controls. Ameliorants were sprayed at active tillering stage (S1), booting stage (S2) and both active tillering and booting stages (S3). Physiological responses were studied from this experiment. Pot culture study showed that ameliorants could improve physiological characters of rice under increasing temperature. Hoagland solution spray enhanced photosynthetic rate, stomatal conductance, IAA content and pollen viability in both the varieties. Increased total soluble protein content, chlorophyll a, chlorophyll b and total chlorophyll was noted in plants sprayed with melatonin. Proline accumulation increased in plants sprayed with glutathione while nitrate reductase enzyme activity improved by salicylic acid. Reduced amount of reactive oxygen species as evidenced by histochemical studies was observed in plants sprayed with ameliorants having antioxidant property, like melatonin, glutathione and ascorbic acid. Spraying of ameliorants at both active tillering and booting stages (S3) was the best followed by spraying at booting stage (S2) alone. Second experiment was carried out in Agronomy farm at College of Horticulture, Vellanikkara during February to June, 2020. Twenty day old seedlings of Uma and Manuratna were transplanted to micro plots of 4 m2. Ameliorants were given as foliar spray at booting stage and one plot of each variety was maintained as control for comparison. Biometric observations and yield characters were studied from this trial. Hoagland solution and salicylic acid treatments increased plant height, RGR and CGR in both the varieties. Reduced tiller decline was also observed in Hoagland solution treated plants. Uma showed higher response to ameliorants than Manuratna. Yield parameters were analyzed by comparing response of ameliorants with control. Plants sprayed with Hoagland solution showed better performance with higher grain yield. It was due to increased number of productive tillers, spikelets per panicle, filled grains per panicle and thousand grain weight. Chaff percentage decreased by application of ameliorants and among them Hoagland solution spray gave the best result. Salicylic acid applied plants had higher straw yield compared to other treatments. Yield performance was better in Uma compared to Manuratna.ThesisItem Open Access Physiological intervention for mitigating temperature stress in rice(Department of Plant Physiology, College of Horticulture , Kerala Agricultural University, Vellanikkara, 2020) Femina, K; KAU; Girija, TRice is an important cereal crop which is most widely consumed as staple food by millions of people. Demand for rice is projected to increase across globe with rapid increase in population. Rice being a tropical crop requires a fairly high temperature for optimum growth and development. However, temperatures above 35 0C cause heat injuries in rice including changes in morphological, physiological and yield characters. Hence, the present study was conducted to identify ameliorative chemicals to mitigate high temperature stress, which is a common occurrence in the third crop season where temperatures can go up to 40 0C in the reproductive stage leading to yield loss. Popular rice varieties, Uma and Manuratna, which are also suitable for the third crop season were chosen for the study. The whole study was divided in to two experiments. The first experiment was carried out in glass house at College of Horticulture, Vellanikkara during January to May, 2019. Ten day old rice seedlings of Uma (V1) and Manuratna (V2) were planted in pots. Treatments included five ameliorative sprays viz. Ascorbic acid (T1), Glutathione (T2), Melatonin (T3), Salicylic acid (T4) and Hoagland solution (T5) along with Water sprayed (T6) and Unsprayed (T7) controls. Ameliorants were sprayed at active tillering stage (S1), booting stage (S2) and both active tillering and booting stages (S3). Physiological responses were studied from this experiment. Pot culture study showed that ameliorants could improve physiological characters of rice under increasing temperature. Hoagland solution spray enhanced photosynthetic rate, stomatal conductance, IAA content and pollen viability in both the varieties. Increased total soluble protein content, chlorophyll a, chlorophyll b and total chlorophyll was noted in plants sprayed with melatonin. Proline accumulation increased in plants sprayed with glutathione while nitrate reductase enzyme activity improved by salicylic acid. Reduced amount of reactive oxygen species as evidenced by histochemical studies was observed in plants sprayed with ameliorants having antioxidant property, like melatonin, glutathione and ascorbic acid. Spraying of ameliorants at both active tillering and booting stages (S3) was the best followed by spraying at booting stage (S2) alone. Second experiment was carried out in Agronomy farm at College of Horticulture, Vellanikkara during February to June, 2020. Twenty day old seedlings of Uma and Manuratna were transplanted to micro plots of 4 m2. Ameliorants were given as foliar spray at booting stage and one plot of each variety was maintained as control for comparison. Biometric observations and yield characters were studied from this trial. Hoagland solution and salicylic acid treatments increased plant height, RGR and CGR in both the varieties. Reduced tiller decline was also observed in Hoagland solution treated plants. Uma showed higher response to ameliorants than Manuratna. Yield parameters were analyzed by comparing response of ameliorants with control. Plants sprayed with Hoagland solution showed better performance with higher grain yield. It was due to increased number of productive tillers, spikelets per panicle, filled grains per panicle and thousand grain weight. Chaff percentage decreased by application of ameliorants and among them Hoagland solution spray gave the best result. Salicylic acid applied plants had higher straw yield compared to other treatments. Yield performance was better in Uma compared to Manuratna.ThesisItem Open Access Physiology and management of submerged weeds in wetland rice ecosystem(Department of Plant Physiology,College of Horticulture, Vellanikkara, 2018) Athira, K A; KAU; Girija, TThe present investigation entitled “Physiology and management of submerged weeds in the wetland rice ecosystem” aimed to identify and characterize the different submerged weed species of wetland rice ecosystem, understand their growth pattern and evolve possible management practices. The study consisted of survey, identification and morphological characterization of submerged weeds of rice ecosystem of the central zone of Kerala. The effect of environmental conditions on growth and multiplication of the most common weed, Utricularia aurea and its control were also studied. Weed survey was conducted in ten locations each in Thrissur, Palakkad and Ernakulam districts of Kerala. Submerged weeds from the rice fields were collected along with soil and water samples from ten locations for further studies. The major submerged weeds in the rice ecosystem included hydrophytes and algal species. Seven hydrophytes and three species of algae were commonly seen in the region. The major hydrophytes were Utricularia aurea, Utricularia exoleta, Elodea canadensis, Hydrilla sp., Egeria densa, Cabomba sp. and Najas sp. while the common algal species were Spirogyra, Chara and Nitella. The water and soil samples collected were analyzed in the laboratory for different physico-chemical properties such as pH, electrical conductivity (EC), total suspended solids (TSS), dissolved oxygen (DO), E. coli content, soil enzymes and hormones which affect growth of the rice plant. pH had the larger influence on growth of submerged weed species. Highest weed growth was observed between pH range of. 7.2 to 8.01 (neutral to alkaline). The presence of submerged weeds reduced the dissolved oxygen content of water and increased the content of TSS and E. coli, adversely affecting water quality and supply of oxygen to rice root. The presence of dissolved nitrate in the water may be a major reason for high incidence of these weeds. Soil enzymes and hormones also positively influenced their growth. The physiological parameters such as chlorophyll content, nitrate reductase activity, indole acetic acid (IAA) and GA contents of the weeds were also studied. It was found that IAA, GA and chlorophyll promoted weed growth. High nitrate reductase was observed in Nitella. Elodea canadensis had the capacity to purify the water by reducing the TSS and improving the dissolved oxygen content. The most common submerged weed in the rice ecosystem was Utricularia aurea and hence this weed was selected to study the effect of light, UV radiation and chemicals on growth and multiplication. Effect of light on weed growth was studied by using different shade nets which allowed 50 per cent and 75 per cent light infiltration. Effect of UV radiation was studied by growing the plants under polyhouse cladded with mylar film which allowed zero UV and polyethylene sheet which allowed 80 per cent UV radiation. Growth and multiplication of Utricularia aurea in the open condition and different light and UV levels were compared. Zero UV and temperature in the range of 30-310C was found to be ideal for weed growth. Both high water temperature and high UV were detrimental. Growth of the weed was not altered with shading, indicating that moderate shade not affect the weed growth. Effect of CuSO4 (1ppm, 2ppm and 3ppm), 2, 4-D (1ppm, 2ppm and 3ppm) and lime (100 ppm, 200 ppm and 300 ppm) on growth of Utricularia aurea was measured by recording the rate of degradation of the weed one month after application in pot culture study. Good control was obtained with higher concentrations of all the three chemicals tried. Three ppm of CuSO4, 2, 4-D and 300 ppm lime gave better results. Lime was found to be more effective in the control of Utricularia aurea.ThesisItem Open Access Spectral manipulation of growth and physiology of Gerbera jamesonii Bolus(Department of Plant Physiology, College of Horticulture , Kerala Agricultural University, Vellanikkara, 2020) Anil, A S; KAU; Girija, TGerbera (African daisy) is one of the most important commercial flower grown throughout the world under a wide range of climatic conditions. Gerbera requires high light intensities for good vegetative growth and flower yield. The average sunshine hours in open condition in the central zone of Kerala during January to May goes upto 8.1 h/day while during June- September is only 3h/day as per 33 year mean data available with the Agro Meteorology Observatory COH, Vellanikkara. This shortage in the sun shine hours can be substituted by the use of external light in polyhouse. When light is provided at the optimal levels it can significantly increase growth rate, health and yield of the crop. The experiment was conducted during the period from July 2018 to September 2019 in polyhouses, at, College of Horticulture, Vellanikkara, to study the influence of spectral light intensities and UV on the morphological, phenological, physiological characters, yield and flower quality of Gerbera (Gerbera Jamesonii Bolus) Tissue culture plants of Gerbera variety Julia developed and marketed by LJ International (AVT Biotechnology) in two leaf stage were directly planted in pots of size 9-inch depth at the rate of one plant per pot. The pots were placed under LED lights of red, blue, green, white and yellow colours kept at a height of one meter from the ground. Plants were illuminated for 10 hours from 09.00 am to 07.00 pm daily from July 28th to September 25 th (2018 to 2019). Observations on morphological characters such as plant height, leaf length, leaf breadth, plant spread, number of lobes, specific leaf area and petiole length were significantly influenced by spectral colors and UV. Among the spectral color’s plants under red and blue showed significant higher morphological attributes compared to other colors. Also, plants under non-UV condition showed greater growth characters as compare to UV condition. Floral evocation was observed when the plants reached five leaf stage. Under red and blue light exposure, plants came to flower in September (49 days from planting) while plants in all other treatments started flowering in October (60 days from planting). Evaluation of photosynthetic rate under different color regimes indicated that maximum photosynthetic rate was under red light. Gas exchange parameters like stomatal conductance, transpiration rate and stomatal frequencies were higher under blue light followed by red light. Also, plants under non-UV condition showed better physiological characters as compare to those under UV condition. Estimation of GA, IAA and chlorophyll content revealed that all the three components were higher in red light followed by blue under non-UV condition. Nitrate reductase enzyme plays a major role in nitrogen metabolism of plants. In the present study, the nitrate reductase enzyme activity was found to be higher in plants grown under red light in non-UV condition. Flower pigments like anthocyanin, xanthophyll, flavonoids were found higher in plants grown under blue light and under UV condition rather than non-UV condition. These constituents are products of secondary metabolic pathway in plants. Flower number and flower quality parameters like number of flowers, flower head diameter, flower stalk length, flower stalk girth and vase life was better under non UV condition than UV condition. These quality characters were seen to be better in plants grown under red and blue light. The study indicated that UV stabilized sheets would be more beneficial than normal polythene sheets and red and blue LED’s can be used to supplement light requirement in polyhouses for commercial cultivation of Gerbera jamesoni Bolus