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Open Access
Mitigation of solar ultraviolet-B radiation induced photoinhibition in photochemistry and photosynthesis of rice (Oryza sativa L.)
(Department of Plant Physiology, College of Horticulture, Vellanikkara, 2016) Shafeeqa, T.; KAU; Nandini, K
Sun light contains ultraviolet (UV) radiation which is separated in to UV-C (100-280nm),UV-B (280-320 nm) and UV-A (320-400nm). Evidences from data collected from both satellite and field experiments indicated an increase in UV-B radiation reaching on the earth surface, due to decrease in ozone layer. Hence, UV-B has become more challenging nowadays causing threat to agriculture production in tropics. UV-B exclusion and enhancement studies conducted in the Department of Plant Physiology, College of Horticulture, Vellanikkara have revealed a decline in rice yield due to UV-B radiation in rice varieties Jyothi and Uma (Wagh, 2015). The present study entitled “Mitigation of solar ultraviolet-B radiation induced photoinhibition in photochemistry and photosynthesis of rice (Oryza sativa L.)” was conducted during 2014-2016 in the Department of Plant Physiology, College of Horticulture, Vellanikkara with the objective to understand the photo protective potential of ecofriendly stress mitigating chemicals on photoinhibition and photosynthesis of rice (Oryza sativa L.) under solar ultraviolet- B radiation. The pot culture experiment was conducted during November 2015 to March 2016 with rice variety Uma under two growing conditions viz. open condition- where the crop exposed to 100% solar radiation and polyhouse condition- which transmit 20% reduced full spectrum solar radiation including UV-B. Three ameliorative chemical treatments with two concentrations such as glycine betaine (10ppm and 20ppm), ascorbic acid (50ppm and 100 ppm) and combination fungicide 25WG trifloxystrobin + 50 WG tebuconazole (Nativo 75 WG- 50ppm and 70ppm) were given as foliar application at 30th and 60th DAT and observations were taken 15 days after each chemical spraying. The experiment was laid out as completely randomized design (CRD). The UV-B and Photosyntheticaly Active Radiation (PAR) in both conditions were monitored regularly throughout the crop period. The data on UV-B and PAR revealed significantly higher UV-B (2.18 Wm-2) and PAR (1786 μmolm-2s-1) during March-2016 under ambient condition. All growth phenophases were delayed under 100% solar radiation. Combination fungicide 25 WG trifloxystrobin+50WG tebuconazole 70ppm enhanced grain filling period under both the growing condition compared to other chemical treatments; the ultimate realization being a relatively good yield. Gas exchange parameters like photosynthetic rate, stomatal conductance and transpiration rate decreased during reproductive phase under 100% solar radiation, where the crop experienced high UV-B radiation. Among chemicals, 25 WG trifloxystrobin+50WG tebuconazole 70ppm enhanced the above parameters by alleviating the photoinhibition in photosynthesis and PSII activities. Photochemical efficiency as indicated by high Fv/Fm ratios was enhanced by foliar application of 25 WG trifloxystrobin+50WG tebuconazole 70ppm. High chlorophyll content, catalase activity and xanthophyll content were observed under reduced UV-B condition. Among chemical treatments significantly higher chlorophyll content was recorded for the rice plants treated with 25 WG trifloxystrobin+50WG tebuconazole 70ppm and this might be the reason for the increased photosynthetic rate in plants due to its application. The maximum yield contributed by 25 WG trifloxystrobin+50WG tebuconazole 70ppm may be due to the enhancement in thousand grain weight and number of spikelet per panicle, more photosynthetic rate and less fluorescence emission / increased photochemical efficiency of PS II, more chlorophyll content, catalase activity and reduction in the synthesis of secondary metabolites like flavanoid and xanthophylls. The ameliorative effect of this chemical has to be explored under field level for better results and recommendation to farmers for raising 3rd crop during puncha season.
Open Access
Spectral management for improving hotosynthetic efficiency in polyhouse cultivation of vegetables
(Department of Plant Physiology, College of Agriculture, Vellayani, 2016) Anjana, J Madhu; KAU; Roy Stephen
Plant growth is influenced by both the quality and intensity of light. The transmittance of light by different shade nets are unique. Hence the spectral quality of light vary under each coloured net. Different wave length of light influence specific physiological process. In this context, the study entitled “Spectral management for improving photosynthetic efficiency in polyhouse cultivation of vegetables” was conducted at the Dept of Plant Physiology, College of Agriculture, Vellayani and at Pothencode, Thiruvananthapuram during 2014- 2016. The main objective was to study the morphological and physiological responses of vegetables, viz. tomato, salad cucumber, capsicum and yard long bean exposed to spectral modification through different colored shade nets. A survey was conducted in 20 polyhouse units in Thiruvananthapuram district to know the adoption of shade nets by the farmers practicing polyhouse cultivation. The experiment was done in a polyhouse of dimension 500m2, which was divided into five parts on an east-west direction roofed with two photoselective and two neutral shade nets of four different optical properties and one part without any shade net. The light interception by shade nets were analysed using spectro radiometer at University of Agricultural Science, Bangalore. The green net reduced 59.9%, white net reduced 55.14% and red net reduced 41.05% of red light compared to open. Four different crops, viz. salad cucumber, yardlong bean, capsicum and tomato were grown under these shade nets. Weather parameters such as Photosynthetically Active Radiation (PAR), global radiation and temperature were recorded but didnot show much variation. The pollen viability was not altered by spectral variation. Earliness to flowering, fruiting and fruit maturity was observed in open condition for salad cucumber and capsicum. The number of leaves at first flowering was higher in white net for salad cucumber and yardlong bean while it was higher in red net for capsicum and tomato. Specific Leaf Area was significantly higher under red net for salad cucumber (979.52cm2g-1), capsicum (564.21cm2g-1) and tomato (631.18 cm2g-1). The same trend was followed in case of photosynthetic rate also. The internode elongation was found to be minimum in open condition for all the four crops. The leaf anatomy of salad cucumber grown under white net showed higher vascular thickness. Setting percentage was higher in white and green shade nets for salad cucumber (85.40%) and yardlong bean (89.35%) respectively where as red net was suitable for capsicum (80.99%) and tomato (81.80%). Higher shoot weight and root weight were observed under white shade net for tomato. Root shoot ratio and total dry matter content was higher in capsicum grown under red shade net. Transpiration rate of yardlong bean and tomato plants grown under green shade net was higher while higher transpiration rate of salad cucumber and capsicum was observed under white shade net. The pigment composition of salad cucumber was higher under black shade net. Abaxial stomatal frequency in all the four crops was higher in open condition. Total soluble protein content of tomato and salad cucumber at flowering stage was higher under red shade net. Higher carbohydrate content was observed under open condition in case of yardlong bean, capsicum and tomato. Phenol content increased in tomato plant grown under white shade net. There was no significant variation in IAA. Higher crude protein was observed in yardlong bean grown under white shade net while the crude fibre was higher under open condition. Ascorbic acid was higher in capsicum grown under open condition while for tomato it was under white shade net. Spectral modifications through shade nets altered morphological and physiological responses of salad cucumber, yardlong bean, capsicum and tomato. Varietal suitability was observed in different shade nets. Photosynthetic efficiency was also influenced by shade nets and reflected in the yield of selected crops. Red net was suitable for capsicum and tomato while white net was ideal for salald cucumber and green for yardlong bean.
Open Access
Carbon dioxide enrichment mediated plant-microbe interaction in cowpea (Vignaunguiculata L.) under water stress
(Department of Plant Physiology, College of Agriculture, Vellayani, 2016) Athibha, P B; KAU; Manju, R V
The level of CO2 in the atmosphere is rising at an unprecedented rate. According to NOAA (National Oceanographic and Atmospheric Administration) 2014, global concentration of CO2 has reached 400 ppm for the first time in recorded history. This rise, along with other trace gases in the atmosphere is widely thought to be a primary factor driving global climate change. Moreover the report of IPCC, 2012 has reconfirmed the increasingly strong evidence of global climate change and projected that the globally averaged temperature of the air would rise by 1.8–6.4°C by the end of the century. Pulses are the main sources of protein and is commonly called poor man’s meat. They are also used as fodder and concentrate for cattle. Pulses are responsible for improving soil fertility by increasing the amount of N2 in the soil. Drought is a recurring problem limiting pulse production in rainfed areas. High frequency of crop failure and yield instability due to biotic and abiotic stresses also contribute to low productivity in pulses. The pulse production scenario is also getting affected by the changing climate and the resulting rise in temperature and decline in rainfall. Under such changing climatic scenario, soil microbes play an important role in the maintenance of physicochemical properties of soil and also in making the soil nutrients available to the plants. In this context, the current programme “Carbondioxide enrichment mediated plant- microbe interaction in cowpea (Vigna unguiculata L.) under water stress ” attempts to study the water stress tolerance character and N2 fixation efficiency of cow pea as influenced by microbial inoculants under elevated CO2 condition. This investigation will help to design improved production technologies with suitable varieties for a changing climatic scenario. Two pot culture experiments were conducted at different carbon dioxide concentrations with three different levels of soil moisture regimes i.e Field capacity, 75% field capacity and 50% field capacity. The cowpea seeds were sown in pots inside OTCs and in open field, one set with microbial seed inoculation and the second set without inoculation. The technology used for subjecting the plants to elevated CO2 environments is the Open Top Chambers (OTC) system. In both set of experiment entire crop period was completed in OTCs. Respective moisture stress levels were imposed during the second month. Experimental plants were maintained for a period of three months. Observations on growth parameters and microbial population studies were done at the end of CO2 exposure period and all the other parameters were taken at monthly intervals. The experiments were laid out in CRD with 18 treatments and three replications. The observations on growth parameters during first month of CO2 exposure on cowpea inoculated with Rhizobium revealed a reduction in specific leaf area by 21.39% under elevated CO2 condition compared to absolute control. Among the physiological and biochemical parameters studied, highest relative water content was recorded under elevated CO2 (4.69%). Carbon dioxide enrichment significantly lowered the stomatal frequency by 28.40 % and transpiration rates by 89.27%. Significant increase in total chlorophyll contents by 50 % was registered under elevated CO2 conditions. Per cent leakage was found significantly lower (38.74%) under CO2 enriched treatment compared to control. Among physiological parameters, a marked rise in phenol content was noticed by 56.68% under elevated CO2. Significant increase in reducing sugars, free amino acid, and ascorbic acid contents by 5.97%, 23.92% and 63.79% was recorded in elevated CO2. Protein content was found decreasing under elevated CO2 by 29.02%. The observations on growth parameters during water stress period in cowpea inoculated with Rhizobium revealed a reduction in specific leaf area by 17.24% under elevated CO2 condition compared to absolute control. Root and shoot dry weights were also found to be higher by 56.08% and 140.77% under elevated CO2 resulting an increase in root shoot ratio by 36.51%. Dry matter production was recorded 116% higher under elevated CO2. Parameters related to nitrogen fixation was recorded lower leaf nitrogen status (17.15% reduction), nitrogen use efficiency (36.46% reduction), and soil nitrogen status (8.79% reduction) under elevated CO2. But the Rhizobial inoculated plants was found to have a positive influence on soil nitrogen status (8.46% increase). Under elevated CO2 tremendous increase in root nodule number plant and nodule dry weight, but Rhizobium doesn't have any significant influence on this parameter. Among the physiological and biochemical parameters studied, highest relative water content was recorded under elevated CO2 (18.57%). Carbon dioxide enrichment significantly lowered the stomatal frequency by 15.53% and transpiration rates by 88.12%. Significant increase in total chlorophyll contents by 13.26 % was registered under elevated CO2 conditions. Per cent leakage was found significantly lower (51.45%) under CO2 enriched treatment compared to control. Among biochemical parameters, significant increase in reducing sugars, free amino acid, phenol, SOD and ascorbic acid contents by 22.63%, 30.65%, 67.56%, 42.12% and 34.06% was recorded in elevated CO2. Protein content was found decreasing under elevated CO2 by 44.92%. Nitrogen fixation efficiency was found to be decreased in terms of reduced leaf nitrogen status under elevated CO2. But nodule number per plant and nodule dry weight were increased. Rhizobial inoculated cowpea plants were observed to have better growth and improved stress tolerance in terms of better leaf water status and membrane integrity under elevated CO2. In the case of cowpea inoculated with P.indica during first month of CO2 exposure, number of leaves (33.30%)was found to be highest under elevated CO2. Lower stomatal frequency (35.78%), transpiration rate (86.89%) and per cent leakage (63.25%) were observed prominently under elevated CO2 compared to open control. Significant increment in reducing sugars by 21.78%, phenol by 77.71%, free amino acid content by 27.42% was recorded under elevated CO2. SOD and ascorbic acid content was found increased by 49.39 % and 8.05 % under elevated CO2 treatment compared with control. Root weight, shoot weight and total dry matter production were found enhanced by 42.39%, 27.27% and 35.31% under elevated CO2 in comparison with control. In the case of water stress also, elevated CO2 was found to have positive influence on growth like number of leaves (57.27%). Significant increment of relative water content (13.933%), total chlorophyll (124.9%), reducing sugar (23.43%), phenol(135.5%) was recorded under elevated CO2 in comparison with control. P. indica inoculated plants under CO2 was found to have better stress tolerance. This was achieved through maintenance membrane integrity and stomatal modifications. There was reduction in stomatal characters like stomatal frequency and stomatal conductance resulting in reduced transpiration and better tissue water status. There were enhanced accumulation and increased activity of antioxidants like ascorbic acid and SOD. This also would have helped the experimental plants in achieving better stress tolerance. The present investigation was carried out with the objective to study the water stress tolerance character and N2 fixation efficiency of cowpea as influenced by microbial inoculants under elevated CO2 condition. Considering all the physiological, biochemical studies conducted, it can be concluded that carbon dioxide enrichment has a positive role on water stress tolerance character of cowpea variety Bhagyalakshmy. There was further enhancement of stress tolerance by both microbial inoculants, Rhizobium sp and P.indica. The underlying tolerance mechanisms were found to be stomatal modifications resulting in reduced transpiration and better tissue water status, activation of antioxidants like ascorbic acid and better maintenance of membrane integrity. Nitrogen fixation efficiency was improved tremendously by elevated CO2 in terms of nodule number per plant and nodule dry weight but leaf nitrogen content and nitrogen use efficiency were reduced by CO2 enrichment. The outcome of the programme reveals the possibility of improving yield potential and stress tolerance under elevated CO2 by integrating photosynthesis and nitrogen use efficiencies with the application of microbial inoculants like P.indica. References
Open Access
Physiological effects of growth stimulants on yield and quality of okra (Abelmoschus esculentus L.)
(Department of Plant Physiology, College of Horticulture, Vellanikkara, 2017) Vishnu, K S; KAU; Sudarsana Rao, G V
Okra or Bhindi (Abelmoschus esculentus L.) is one of the most popular summer vegetable crop grown widely in Kerala. It accounts for 65 % of the fresh vegetables exported from the country. However, the productivity of the crop is low in the state. The low fertility status of the soil due to heavy rains may be a major reason. Currently, for sustainable increase in productivity soil test based nutrient management practices are recommended. Another approach is the use of environment friendly growth stimulants, which have beneficial effects on plants. Hence, the present study was carried out to understand the influence of growth stimulants on growth, yield and quality attributes of okra variety Arka Anamika under standard package of practices (POP) recommended by KAU and also soil test based nutrient management system. The experiment was laid out in Randomized block design with 15 treatments and three replications at Central nursery, College of Horticulture, Vellanikkara. The crop was raised as per standard POP recommendations of KAU and also under soil test based nutrient management system. Experiments consisted of 15 treatments viz., standard POP, KAU (T1) as control, soil test based modified nutrient management (T2), T1 + humic acid spray @ 0.2 % (T3), T1 + potassium silicate spray @ 0.3 % (T4), T1 + cytozyme spray @ 0.2 % (T5), T1 + putrescine spray @ 50 ppm (T6), T2 + humic acid spray @ 0.2 % (T7), T2 + potassium silicate spray @ 0.3 % (T8), T2 + cytozyme spray @ 0.2 % (T9), T2 + putrescine spray @50 ppm (T10), 50 % T1 + humic acid spray @ 0.2 % (T11), 50 % T1 + potassium silicate spray @ 0.3 % (T12), 50 % T1 + cytozyme spray @ 0.2 % (T13), 50 % T1 + putrescine spray @ 50 ppm (T14) and T1 + water spray (T15). Foliar application of growth stimulants was given at 15, 30 and 45 DAS. Morphological, physiological and biochemical parameters were recorded at 25 and 50 DAS and the yield and fruit quality characters were recorded at the time of harvest. The use of growth stimulants such as humic acid, cytozyme and potassium silicate with soil test based nutrient management system improved the morphological parameters like plant height, leaf area, the number of leaves per plant etc. than control. Plants which received potassium silicate, putrescine and humic acid as foliar spray recorded higher total chlorophyll content and IAA content. Comparison of photosynthetic rate, transpiration rate and stomatal conductance of crop at two different growth stages revealed that growth stimulants such as humic acid, cytozyme and potassium silicate along with soil test based nutrient management showed a significant improvement over control. A similar pattern of the effectiveness of growth stimulants was observed in the case of fruit yield and quality characters such as crude fiber content, ascorbic acid content, mucilage content and total protein content. Comparison of POP, soil test based application of fertilizers and 50 per cent POP showed that soil test based nutrient management gave significantly higher yield as compared to the other treatments including control. The response of the stimulants was also higher for soil test based nutrient management treatments. Growth stimulants with soil test based nutrient management applied plots recorded 12 to 23 per cent higher fruit yield over control followed by standard POP with growth stimulants which recorded an improvement of 5 to 9 per cent over control. Reduction in fruit yield of 3 to 6 per cent was recorded with 50 per cent standard POP over control. Among the four growth stimulants used, humic acid performed better followed by cytozyme and potassium silicate. These growth stimulants may have enhanced the nutrient use efficiency of the plants which further improved the photosynthesis, plant growth and development. The result of the present study indicated that growth stimulants can be recommended along with soil test based nutrient management for enhancing crop growth, fruit quality and yield of okra.
Open Access
Identification of microsatellite markers associated with root traits for drought tolerance in rice (Oryza sativa L.)
(Department of Plant Technology, College of Agriculture, Vellayani, 2017) Rejeth, R; KAU; Beena, R
The present investigation entitled “Identification of microsatellite markers associated with root traits for drought tolerance in rice (Oryza sativa L.)” was conducted at Department of Plant Physiology, College of Agriculture, Vellayani during 2016-17. The objective of the study was to validate the role of root traits in rice for drought tolerance and to identify the microsatellite markers associated with root traits for drought tolerance in rice. The extend of variation for water stress indicators, physio-morphological and yield components were assessed by evaluating 35 rice genotypes collected from RARS, Pattambi under water stress and irrigated conditions in the rainout shelter. The rice accessions grown in polythene tubes of 1 meter height were exposed to water stress at panicle initiation stage for a period of 15 days along with irrigated control. The physio-morphological, biochemical and yield components were recorded on completion of stress period. Significant variation was observed for these traits and ten drought tolerant and ten drought susceptible genotypes were selected. The genomic DNA was isolated from these rice genotypes and were pooled into drought tolerant and susceptible bulks. Bulked line analysis was carried out to identify microsatellite markers linked to drought tolerance in rice. The result of the study revealed that physiological parameters such as Relative Water Content (RWC), photosynthetic rate, transpiration rate and stomatal conductance decreased where as proline content and leaf temperature increased significantly in most of the genotypes under water stress condition. Highest leaf rolling (score – 9) was observed in Ptb–7 and Ptb-13 while the genotypes Ptb–29 and Ptb-30 showed no leaf rolling symptoms (score – 1). Among the genotypes, the RWC was recorded to be highest in Ptb–4 while the lowest was recorded in Ptb–13 under water stress condition. The percentage decrease in RWC compared to irrigated control was less in Ptb–15. Membrane stability index was more in Ptb–29 (98.5 %) and Ptb-10 (98.1 %) as compared to other genotypes under water stress condition. Maximum leaf temperature was observed in Ptb–1(31.70C) and minimum in Ptb–7 (27.80C) under water stress condition. Among the genotypes, stomatal conductance was recorded to be highest in Ptb–30 (674 m moles m-2 s-1) while the lowest in Ptb– 20 (92 m moles m-2 s-1). The photosynthetic rate decreased significantly under water stress condition with maximum in Ptb–30 (15.2 μ moles m-2 s-1) and minimum in Ptb–6 (3.4 μ moles m-2 s-1). Under water stress condition, maximum transpiration rate was observed in Ptb–4 (1.4 m moles m-2 s-1) and minimum in Ptb–31 (0.05 m moles m-2 s-1). Proline content increased at 50% flowering stage in water stress condition with maximum accumulation in Ptb–27 and minimum in Ptb–22. At flowering stage highest root length was noticed in Ptb-15 and lowest for Ptb–3 and Ptb-8 under water stress condition. Root volume differed significantly in several genotypes with maximum in Ptb–21 and minimum in Ptb-31. Root dry weight decreased in water stress compared to control in most of the genotypes with highest in Ptb-13 and lowest in Ptb-31. Root shoot ratio was found to be highest in Ptb-29 and Ptb-30 and lowest in Ptb-31. The plant height at maturity was observed to be highest in Ptb-1 and lowest in Ptb-34 under water stress condition. Days to 50% flowering reduced in most of the genotypes under water stress condition compared to irrigated control. Productive tiller number of most of the genotypes significantly reduced in water stress condition with maximum reduction in Ptb-28. Maximum yield under water stress was recorded in Ptb-55 and minimum in Ptb-21. Number of filled grains and unfilled grains were observed as major attributes affected drastically under water stress condition. The spikelet fertility percentage was highest in Ptb-25 and lowest in Ptb-1. Ptb-28 had maximum 1000 grain weight under water stress and minimum was for Ptb-17. Correlation study revealed that grain yield per plant under water stress condition was positively correlated with parameters such as relative water content, membrane stability index, proline content, stomatal conductance, photosynthetic rate, transpiration rate, root length, root shoot ratio, spikelet fertility % and 1000 grain weight where as negatively correlated with leaf temperature, leaf rolling score, root volume, root dry weight, plant height, days to 50% flowering and panicle length. In Bulked Line Analysis, out of the 150 microsatellite primers screened only one marker i.e., RM 474 showed polymorphism between the tolerant and susceptible bulks. The same primer showed similar product size (252bp) among the individual lines which constituted respective bulks. In summary, there was significant variation for physio-morphological and yield components among rice genotypes under water stress condition. Genotypes having higher root length and root shoot ratio were found to be tolerant to drought. The genotypes identified as drought tolerant viz Ptb-29, Ptb-30, Ptb-15, Ptb-1, Ptb-55 etc. can be used in breeding programmes to improve drought tolerance in rice. Microsatellite marker RM 474 which could distinguish drought tolerant and susceptible bulks can be used for marker assisted selection for drought tolerance in rice.
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, T
Sesame 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.
Open Access
Physiological characterization of thermo-sensitive genic male sterility in rice (Oryza sativa L.)
(College of Agriculture, Vellayani, 2016) Neethu, Chandra C; KAU; Roy, Stephen
The study entitled ‘Physiological characterization of thermo-sensitive genic male sterility in rice (Oryza sativa L.)’ was carried out at College of Agriculture, Vellayani during 2014-16. The main objective of the study was to develop thermo-sensitive genic male sterile line in red rice background and its physiological and phenological characterization. The TGMS line from International Rice Research Institute (IRRI), EC720903 and red rice varieties, Uma and Jyothi were used in this experiment. TGMS plants become male sterile at high temperature and male fertile at low temperature. Seed multiplication was done at Regional Agricultural Research Station (RARS), Ambalavayal where the temperature is low. The work was done in three experiments. Experiment I. Development and evaluation of male sterile F2 plants. The TGMS line as well as Uma and Jyothi were grown in pots for hybridization. First flowering, 50% flowering, crossing and maturity dates were noted and F1 seeds were obtained. F2 seeds were collected pollen and spikelet sterility were recorded. The TGMS line was found to be a suitable female parent as it exhibited synchronous flowering and had 100% sterility with pollen free anthers at Vellayani conditions. Experiment II. Physiological and phenological characterization of thermo-sensitive male sterile line. F2 seeds developed were used for this experiment. Seeds were sown at monthly interval and the critical sterility point was identified. Pollen sterility and spikelet sterility of F2 plants were monitored. Those plants which were sterile at Vellayani were taken to Ambalavayal for confirming the TGMS character in ratoon crop. The TGMS seeds were multiplied at RARS Ambalavayal where the season suitable for seed multiplication was noted. From these plants more than 200 red seeds were collected. The F2 plants exhibited similar flowering duration as that of the TGMS parents. The sterile plants were showing sterility characters similar to that of the female parent (TGMS) with pollen free anthers and100% spikelet sterility. From the temperature data of Vellayani, critical sterility point (CSP) was found to be 26.10 C above which the TGMS plants showed complete sterility. The total free amino acid content in F2 plants was higher in sterile plants than in fertile. The weather data from Amblavayal clearly indicates the reliability for seed multiplication at Ambalavayal where the mean temperature is always less than 250 C. Experiment III. Samples were collected from sterility inducing and fertility inducing conditions, simultaneously and analysed for various biochemical parameters like chlorophyll, total free amino acids, proline, phenolic compounds, Superoxidedismutase (SOD), Malondialdehyde (MDA), ascorbate content, auxin, and total soluble proteins. Chlorophyll was found to be higher in sterile plants than in fertile plants. Total free amino acids, proline, phenolic compounds, SOD, MDA, ascorbate content, auxin, and total soluble proteins were higher in sterile plants. The study revealed that CSP of the TGMS line under study is 26.10 C. It can be used as a reliable female parent in rice breeding programme. TGMS red rice under Jyothi background was developed. The presence of higher amount of MDA, SOD, ascorbate, phenol etc. in sterile plants clearly indicates a higher level of oxidative stress experienced by TGMS plants under sterility inducing condition which may be leading to the expression of sterility.
Open Access
Mitigating the phytotoxic effect of ALS inhibiting herbicides in rice (Oryza sativa L.)
(College of Horticulture, Vellanikkara, 2016) Nithya, N; KAU; Girija, T
The 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.
Open Access
Carbon dioxide enrichment induced drought tolerance responses in tomato (Solanum lycopersicum L.) and amaranthus (Amaranthus tricolor L.)
(Department of Plant Physiology,College of Agriculture,Vellayani, 2016) Dheeraj, Chatti; KAU; Manju, R V

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