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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 Evaluation of CO2 enrichment on growth, development and soft rot tolerance in ginger (Zingiber officinale Rosc.)(Department of Plant Physiology, College of Agriculture, Vellayani, 2021) Manasa, R; KAU; Manju, R VThe present investigation entitled “Evaluation of CO 2 enrichment on growth, development and soft rot tolerance in ginger (Zingiber officinale Rosc.)” was undertaken with the objective to assess the impact of elevated CO 2 on growth, yield, quality and tolerance to soft rot in ginger through morphological, physiological, biochemical and molecular analysis. Two sets of pot culture experiments were conducted during 2017- 2019. The technology utilized for CO 2 enrichment was Open Top Chamber (OTC) system established under Department of Plant Physiology, College of Agriculture, Vellayani. In the first experiment three varieties of ginger Aswathy, Athira and Maran were utilized to assess the impact of elevated CO 2 on growth, yield and quality of ginger. One set of three month old plants were shifted to OTC and another set was retained under ambient CO 2. The plants were harvested at 4 th , 5 th , 7 th and 8 th months after planting (MAP). Observations on growth, physiological and biochemical parameters were recorded at each harvest. Yield, yield parameters, tissue nutrient status and quality parameters were assessed at 8 MAP. Second experiment was conducted to assess the impact of elevated CO 2 on tolerance to soft rot in three ginger varieties Aswathy, Athira, Maran and wild ginger congener Zingiber zerumbet. One set of three and a half month old plants were shifted to OTC and another set retained at ambient CO 2 and were challenged with Pythium aphanidermatum at 4 MAP. The CO 2 concentration of 500 ppm was maintained in the OTC. The results of the first experiment indicated an improvement in growth parameters like plant height, number of leaves, root weight, shoot weight, stem diameter and number of tillers, physiological and biochemical parameters like total chlorophyll, photosynthetic rate and total sugars in the rhizome by recording significantly higher values upon CO 2 enrichment when compared to ambient CO 2 condition. Significant reduction in transpiration rate, stomatal conductance and specific leaf area were recorded upon CO 2 enrichment. The per cent increase in yield parameters like number of fingers (38.19%), rhizome spread (11.32%), thickness (42.72%) and dry weight of rhizomes (31.43%) recordedhigher values upon CO 2 enrichment, based on average performance of all the selected varieties, leading to greater yield. The per cent increase in the fresh weight of rhizome recorded higher for variety Aswathy (38.34%), followed by Maran (20.00%) and Athira (12.12%) with a total fresh rhizome yield of 165.35 g plant -1 under ambient and 228.75 g plant -1 under elevated CO 2 condition in the case of Aswathy. Upon CO 2 enrichment the quality of rhizome was modified with increase in fiber (60.26%), gingerol (9.06%), phenol (19.25%), total oleoresin (11.52%), starch (44.84%) and essential oils (31.10%). Significant reduction in protein and nutritional status in the rhizomes were also recorded. Nitrogen, potassium, iron and zinc contents decreased by 15.78%, 3.22%, 11.78% and 18.57% respectively. Phosphorous and copper showed decrease in trend though not significant. Among the three varieties of ginger, Aswathy was found to be performing better compared to Athira and Maran not only in terms of yield, also for majority of quality parameters assessed upon exposure to elevated CO 2 condition. In the case of impact of elevated CO 2 on soft rot development, there was no variation in the per cent disease incidence. However, lesser number of days was taken for development of symptom. The per cent disease index was reduced by 11.10% upon CO 2 enrichment. The reduction in the fresh weight of rhizome upon pathogen inoculation was also less under elevated CO 2 (14.34%) when compared to ambient CO 2 (17.60%) showing that increasing CO 2 levels might bring down the disease severity. Upon P. aphanidermatum inoculation, the retention of photosynthetic pigments like chlorophyll a (0.90 mg g -1 FW) chlorophyll b (0.74 mg g -1 FW) total chlorophyll (1.64 mg g -1 FW) carotenoids (0.58 mg g -1 FW), xanthophyll (0.40 mg g -1 FW) and photosynthetic rate (5.92 μmol CO 2 m -2 s -1 ) were higher under elevated CO 2 when compared to ambient CO 2 . Higher membrane integrity values and lower malondialdehyde (0.75 μg g -1 FW) content in all the selected varieties were evident upon pathogen inoculation under CO 2 enrichment. Enhanced activity of ascorbate peroxidase (4.86 activity Units mg -1 total protein), PAL (Phenylalanine ammonia lyase) (20.91 Units mg -1 total protein), and glucanase (4.57Units mg -1 total protein) activity, as well as higher accumulation of phenols (32.40 mg g -1 DW) and ascorbic acid (7.14 mg 100 g -1 FW) were found in the inoculated plants under CO 2 enrichment compared to the ambient CO 2 . The catalase activity was found to reduce upon pathogen inoculation and the reduction was higher (0.11 Units mg -1 total protein) under ambient CO 2 as compared to elevated CO 2 (0.09 Units mg -1 total protein). Highest levels of hydrogen peroxide, superoxide and cell death were observed upon pathogen inoculation under ambient CO 2 through staining techniques and it was highest for variety Aswathy and least for Z. zerumbet. After pathogen inoculation maximum values for variable to maximum fluorescence Fv/Fm (0.63), photosynthetic electron transport rate (82.60 micro equiv m -2 s -1 ) and quantum yield of PS II photochemistry (0.29) were recorded under elevated CO 2. Protein profiling performed in varieties Athira and Aswathy revealed lower expressions of 20-25 kDa and 25-35 kDa protein under pathogen inoculation in variety Aswathy. The expression of 55 kDa (Rubisco Large Sub- Unit) was down regulated to a greater extent under pathogen inoculation in both the varieties. Higher expression levels of the defense responsive genes Phenylalanine ammonium-lyase (PAL), Cinnamyl alcohol dehydrogenase (CAD) and Chalcone synthase (CSH) were also observed upon pathogen inoculation under CO 2 enrichment in both the varieties. Between the varieties, Athira had higher relative fold changes of PAL, CAD and CSH under both ambient and elevated CO 2 upon pathogen inoculation. The present study revealed that CO 2 enrichment can improve the performance of ginger in terms of growth, yield and quality. It also indicates changes in photosynthetic allocation pattern and phytochemical profiles with enhanced contents of oleoresins and essential oils. Ginger plants showed better tolerance against P. aphanidermatum upon CO 2 enrichment. This was apparent in the form of reduced disease severity, oxidative stress level and less reduction in yield upon pathogen infestation under elevated CO 2 condition. This was evidently achieved through the activation of multiple mechanisms, including enhanced production of anti-oxidants and up regulation of pathogen resistance proteins. This is one of the first studies to comprehend on possible effects of elevated CO 2 on the susceptibility of ginger to soft rot. The study also demonstrated the varietal variations existing in the response to CO 2 enrichment which will help in selection ofsuitable varieties for changing climatic scenario. The information generated indicates the possibility of enhancing both qualitative and quantitative yield of ginger through low cost CO 2 enrichment technologies. The insights obtained on the tolerance mechanisms involved will help to restructure the soft rot disease management strategies in the coming future.ThesisItem Open Access Physiological biochemical and molecular studies in medicinal rice (Oryza sativa L.) Njavara as influenced by abiotic stresses(Department of Plant Physiology, College of Agriculture, Vellayani, 2020) Wagh Yogesh, Sahebrao; KAU; Viji, M MThe study entitled “Physiological, biochemical and molecular studies in medicinal rice (Oryza sativa L.), Njavara, as influenced by abiotic stresses” was conducted during 2015 to 2019 at the Department of Plant Physiology, College of Agriculture, Vellayani, Thiruvananthapuram. The objective of the study was to elicit information on the physiological, biochemical and molecular attributes associated to secondary metabolites accumulation due to abiotic stresses viz., shade, drought and UV-B stress in medicinal rice Njavara. The study was conducted as three different experiments with black glumed and yellow glumed njavara. Experiment one was a pot culture study laid out in Completely Randomized Design (CRD) with two varieties and five treatments. The study included a combination of two levels of shade stress and two levels of water deficit stress and a control with four replications and with three pots in each replication. The observations were taken at different critical stages of the crop viz., vegetative stage, panicle initiation stage, flowering stage and harvesting stage. The results revealed that the morphological characters such as plant height, leaf area index and specific leaf area were higher under 40% shade whereas under 50% field capacity, they were found to be highly reduced. Number of tillers per plant was higher under control (T5) compared to shaded and water deficit conditions. Leaf gas exchange parameters viz., photosynthetic rate, stomatal conductance and transpiration rate were lesser under both experimental conditions compared to the control. However maximum reduction of leaf gas exchange parameters were recorded at 50% field capacity (T3) followed by 40% shaded condition (T2) compared to the control (T5). Among the biochemical characters, maximum chlorophyll content was found under 40% shaded condition (T2). The biochemical parameters such as flavonoid, phenol and proline content of leaves were found higher under 50% field capacity (T3) at all the growth stages studied. The total flavonoid content in the grains was found higher under 75% field capacity (T4) followed by 20% shade treatment (T1) in both the varieties. The second experiment was carried out in pot culture in CRD with four treatments, three replications and four pots per replication. The crop was subjected to UV-B (280-320 nm) radiation with the help of UV-B fluorescent tubes during the different critical stages of plants i.e. from vegetative stage, from panicle initiation stage and from flowering stage till harvesting in ventilated polyhouse. The UV-B tubes were switched on for 4 hours daily from 10 am to 2 pm and the average intensity of UV-B radiation at the canopy level of plants was maintained at 4 Wm-2. The control was maintained in another compartment of polyhouse without UV-B tubes. The results indicated that the morphological characters viz., plant height, leaf area index, specific leaf area and tiller number reduced significantly under UV-B radiation treatment and the maximum reduction was observed in treatment T1 (UV-B treatment from vegetative stage). Leaf gas exchange parameters as well as chlorophyll content decreased significantly under UV-B radiation treatments compared to the treatment without UV-B radiation. However flavonoid, phenol and proline contents of leaves were found to increase under UV-B treatments (T1, T2 and T3). The accumulation of total flavonoid in grains was found significantly higher in treatment T2 (UV-B radiation treatment given from panicle initiation stage) in both the varieties. The treatments which resulted in the highest accumulation of flavonoid content in grains were selected from experiment 1 (20% shade and 75% field capacity) and experiment 2 (UV-B radiation treatment from panicle initiation stage) for molecular analysis in experiment 3. Protein profiling was done in leaves using SDS-PAGE in which, there was variation in the intensity of large subunit (55 kDa) as well as small subunit (16 kDa) of RuBisCO, between the varieties and the treatments. The intensity of those bands were found higher in 20% shade (T1), 75% field capacity (T2) and control (T4) whereas under UV-B radiation treatment from panicle initiation stage (T3) relatively lesser intensity was exhibited. Gene expression study in grains using qRT-PCR revealed relatively higher expression of chalcone synthase (CHS) and CYP75B4 genes in black glumed njavara (V1) than the yellow glumed njavara (V2) variety. Also the gene expression study revealed that both the genes were over expressed under T3 (UV-B radiation treatment from panicle initiation stage) and T2 (75% field capacity). But both the genes (CHS and CYP75B4) were found down regulated under T1 (20% shade) condition. The present study revealed that the flavonoid content in grains is higher in black njavara (V1) compared to yellow njavara (V2). The study also indicated that the various parameters studied viz., growth, physiological and biochemical were found to have positive influence on the flavonoid accumulation of grains. But the chlorophyll content was found to have negative influence on the flavonoid content of grains. Proline content was less in black njavara (V1) under UV-B radiation compared to yellow njavara (V2). Based on the present study it is concluded that the black glumed njavara performed better than yellow glumed njavara under all the stress conditions studied and can be exploited better for its therapeutic value. Application of mild stress levels viz., water deficit (75% field capacity) or UV-B radiation treatment from panicle initiation stage may be utilized to enhance the medicinal quality of this crop.ThesisItem Open Access Identification of molecular markers and quantitative trait loci(QTLs)associated with drought tolerant and plant production traits in rice(Oryza sativa L.)using association genetic analysis(Department Of Plant physiology, College Of Agriculture, Vellayani, 2020) Nithya, N; KAU; Beena, RThe present investigation entitled “Identification of molecular markers and Quantitative Trait Loci (QTLs) associated with drought tolerant and plant production traits in rice (Oryza sativa L.) using association genetic analysis” was conducted at Department of Plant Physiology, College of Agriculture, Vellayani and RARS, Pattambi during 2016-18 . The objective of the study was to identify molecular markers, Quantitative trait loci (QTLs) associated with drought tolerance and plant production traits in rice under drought condition. The extend of variation for water stress indicators for morpho-physiological and plant production traits were assessed by evaluating 81 rice genotypes collected from RARS, Pattambi and NRRI, Cuttack under water stress and irrigated conditions in the open field. Each genotype was raised in four rows of 2m length and was exposed to water stress at panicle initiation stage for a period of 25 consecutive days by withdrawing irrigation along with irrigated control and replicated twice. The morpho- physiological, and plant production traits were recorded after imposing water stress. Significant variation was observed for these traits under water stress condition. Genotyping of 81 rice genotypes were done using 100 SSR primers. Quality and quantity of DNA was checked. Amplification pattern of 100 primers were scored as per standard procedure. Population structure was calculated using the software “STRUCTURE” with genotypic score value. The molecular markers/ QTLs linked to drought tolerance and plant production traits were identified using the software, TASSEL 5. The result of the study revealed that morphological parameters such as the plant height at flowering was observed to be highest in PTB1 and lowest in ASD-16 under water stress condition in both experiments. The number of tillers were maximum for PTB7 (10.5 plant-1) and minimum for Kuttithekkan under water stress condition in both experiments. Delayed days to 50% flowering (7 days) was observed for the genotypes under water stress in two experiments compared to irrigated control. Physiological parameters such as Relative Water Content (RWC) decreased where as leaf temperature increased significantly in most of the genotypes under water stress condition. Highest leaf rolling (score – 7.78) was observed in Prathyasha in both experiment I (7.78) and experiment II (7.84). But the genotypes PTB55 (1.78) & PTB 29 (1.11) showed least leaf rolling symptoms in both experiment I and II respectively. Among the genotypes, the RWC was recorded to be highest in PTB15 (78.72%) while the lowest was recorded in Prathyasha (57.34%) under water stress condition in experiment I and in experiment II maximum relative water content was observed in PTB27 (72.98%) and minimum in ADT37 (50.25%). Membrane stability index was highest in PTB29 in experiment I (94.36 %) and in PTB27 in the experiment II (92.24%). Maximum leaf temperature was observed in PTB1 and minimum in Prathyasha under water stress condition in both experiments. Among the genotypes, chlorophyll stability index was recorded to be highest in PTB27 (95.59%) while the lowest in Pandichempan (80.36%) in experiment I, and in experiment II maximum was recorded in variety PTB7 (92.85%) and minimum in Pandichempan (75.52 %). The grain yield per plant under water stress condition was positively correlated with parameters such as tiller numbers, days to 50% flowering, relative water content, membrane stability index, chlorophyll stability index , spikelet fertility percentage and 1000 grain weight where as negatively correlated with leaf temperature, leaf rolling score, leaf drying score and percentage relative yield reduction. Under water stress the first principal component showed 41.77% variation, while second component exhibited 16.57% variation. Among the 14 morpho-physiological and plant production traits, relative water content, cell membrane stability index and chlorophyll stability index contributed towards maximum diversity. Under irrigated control condition the first principal component revealed 48.9 % variation, while the second component showed 16.57% variation. Among the 8 morpho-physiological and plant production traits studied, the relative water content and spikelet fertility percentage contributed towards maximum diversity. Clustering by Ward method was done to establish a relationship among the 81 rice genotypes. Similar types of genotypes were clustered together based on the phenotypic data. All the genotypes were clustered mainly into 5 clusters under water stress as well as irrigated control condition. Genotyping of eighty one rice genotypes were done using 100 SSR markers. Among them, 40 primers which demonstrated polymorphism among the genotypes were used to classify the genomic regions (QTLs) associated with drought tolerance and plant production traits through association genetic analysis. The marker trait association for all the traits under water stress and irrigated control condition were calculated using GLM and MLM model of TASSEL5 software. A total of 136 marker trait associations were observed while performing GLM analysis and MLM analysis resulted in 48 marker trait association based on the P and r2values in water stress as well as irrigated control condition. LD was distributed unequally on each chromosome and more concentrated on chromosomes 1 and 7. LD analysis in the whole population showed that there were significant LD pairs (P<0.05). A total of 52 LD pairs were observed under water stress and irrigated control conditions and out of these, there were 46 inter chromosomal LD pairs and 6 intra chromosomal LD pairs. The markers RM3825, RM455, RM490, RM259 and RM1026 showed significant associations with many phenotypic traits in water stress as well as irrigated control conditions. The Q-Q (Quantile-Quantile) plot also confirmed the association of these markers with phenotypic traits. In summary, there was significant variation for morpho-physiological and plant production traits among rice genotypes under water stress condition. Genotypes having higher relative water content, cell membrane stability index and chlorophyll stability index were found to be tolerant to drought. In the present study, the genotypes viz PTB28, PTB29, PTB30, PTB15, PTB7, PTB55, N-22 and Chomala identified as drought tolerant can be used in breeding programmes to improve drought tolerance in rice. From this study, 29 significant (P<0.05) marker trait associations were detected using mixed linear model (MLM). The identified most significant markers and their corresponding QTLs are, RM455 (Chromosome7) was linked to tiller number, leaf temperature, relative water content, yield per plant and spikelet fertility percentage. RM490 (Chromosome1) was associated with leaf temperature and chlorophyll stability index. Marker RM259 (Chromosome1) was associated with leaf temperature, chlorophyll stability index, leaf drying score, yield per plant and spikelet fertility percentage. RM1026 (Chromosome 9) was associated with leaf rolling score and drying score. Among them, RM 490 and RM259 showed co-location of QTLs for leaf temperature and chlorophyll stability index and RM259 & RM1026 showed co-location of QTLs for leaf drying score.ThesisItem Open Access Evaluation of CO 2 enrichment effects on resource utilization in cowpea and amaranathus(Department of Plant Physiology, College of Agriculture, Vellayani, 2019) Srikanth, G A; KAU; Manju, R VThe current experiment entitled "Evaluation of CO2 enrichment effects on resource utilization in cowpea (Vigna unguiculata L.) and amaranthus (Amaranthus tricolor L.)" was undertaken with the objective to study the impact of CO2 enrichment on cowpea and amaranthus imder varying moisture, temperature and nutrient regimes. Four sets of pot culture experiments were conducted during 2015 to 2018 with two varieties of cowpea, Lola and Vellayani Jyothika and Arun variety of amaranthus. The technology used for CO2 enrichment was Open Top Chamber (OTC) system established under Department of Plant Physiology, College of Agriculture, Vellayani. Carbon dioxide was released from CO2 cylinders to one of the two OTC's bringing the CO2 level to 600 ppm and the second OTC worked as control at ambient CO2 for chamber effect. The experiments were laid out in CRD factorial. First experiment was conducted to study the varietal variation in cowpea in response to CO2 enrichment through OTC. Experimental plants were maintained in OTC from sowing to harvest. Observations were taken at biweekly intervals till 3 months. In this study highest values were recorded in variety Lola for number of leaves per plant (79.5), specific leaf area (208.78 cm^g"'), root weight (14.91 g), shoot weight (65.05 g), root shoot ratio (0.229), total dry matter production (79.98g), single pod weight (12.88 g), number of seeds per pod (12.34) and early flowering was also observed under elevated CO2 condition. In Vellayani Jyothika, highest values were recorded for number of pods per plant (11.75), total yield (102.59 g/plant) and total chlorophyll content (0.897 mg g"^), stomatal frequency (2203.84 cm'\ starch (14.26 mg g"') and reducing sugar (15.97 mg g"'), and fibre content (1.34 mg g"') under elevated CO2 condition. Parameters like total soluble protein recorded lower values (8.75) under CO2 enrichment. Quality parameters were modified with a reduction in total protein content (15.76, 14.75 mg g"') and increase in fibre content (1.34, 1.23 mg g '). Among the two varieties of cowpea, Vellayani Jyothika was found to be the best responding variety to elevated CO2 in terms of yield parameters and so was selected for further experiments. In the second experiment evaluation of plant response to elevated CO2 under different soil moisture regimes were evaluated. Two weeks old potted plants were shifted to OTCs. All the three sets of plants were maintained at field capacity (FC) initially. Soil moisture levels were brought down to 80% and 70%, in the second and third sets 30 days after planting and were maintained for a period of 30 days at these soil moisture regimes in OTCs. The result indicated an improvement in growth performances of cowpea and amaranthus under mild and severe moisture stress conditions (80% and 70% FC) in terms of increased number of leaves (46.82, 43.22), specific leaf area (360.43, 261.58 cm^ g-') root weight (9.02, 8.51 g), shoot weight (30.56, 22.16 g), root shoot ratio (0.327, 0.216) and dry matter production (38.98, 29.67g) respectively. The same trend was found in the case of amaranthus for number of leaves per plant (41.00, 37.66), specific leaf area (171.25, 157.59 cm^ g'), plant height (79.66, 72.32 cm), root weight (0.840, 0.416 g), shoot weight (4.740, 3.031 g), root shoot ratio (0.197, 0.130) and dry matter production (4.82, 4.71 g). In the case of cowpea CO2 enrichment induced early flowering in all the three soil moisture conditions. Significant increase in yield was also obtained under stress condition (78.51 and 77.08 g/plant) due to increase in number of pods per pod (8.67, 7.32), single pod weight (11.63, 10.36 g), number of seeds per pod (9.33, 8.75) both under 80% and 70% PCs. In cowpea, total chlorophyll content (1.671, 1.238 mg g"'), RWC (85.24, 77.97 %), stomatal frequency (2144.00, 1964.53 no cm"^), starch (6.12, 5.69 mg g"'), reducing sugar (12.48, 12.09 mg/g), phenol content (0.943, 0.801 mg g') free amino acid content (5.960, 4.823 mg/g), SOD activity (3.466, 4.230 g-Wnute-'), ascorbic acid content (6.87, 5.84 mg/lOOg). Reduction of transpiration rate (0.547, 0.335 mmol water m-^ s"') total soluble protein (6.02, 5.13 mg g'^), membrane integrity (% leakage) (37.80, 34.61%) under CO2 enrichment after stress. The same trend was found in the case of amaranthus total chlorophyll content (1.245, 1.206 mg g"'), RWC (84.98, 79.37%), stomatal frequency (691.16, 573.78 no cm'^), reducing sugar (17.61, 13.56 mg g"'), starch (2.66, 2.53 mg g"'), phenol content (6.20, 3.53 mg g"') free amino acid content (1.071, 1.036 mg g'), SOD activity (1.842, 1.526 g-'minute-'), ascorbic acid content (36.93, 28.40 mg/lOOg), reduction of transpiration rate (2.093, 1.410 mmol water m- s ) total soluble protein (15.42, 15.06 mg g '), membrane integrity (3.480, 3.017%) under elevated CO2. Evaluation of plant responses to elevated CO2 under different soil nutrient regimes was earned out in the third experiment. Potted plants of cowpea and amaranthus (Variety Arun) were used for conducting the experiment. Plants were maintained at FC at four nutrient levels throughout the crop period. The best performance given by plants receiving nutrients as per POP recommendation along with 25% extra nitrogen In cowpea, the values were recorded as follows, number of leaves (76.00), specific leaf area (468.95 cm^ g"^), dry root weight (42.0%), dry shoot weight (0.5%), root shoot ratio (4.9%). total dry matter production (117.58 g), number of pods per plant (16.66), single pod weight (15.83 g), number of seeds per pod (13.33) and total yield (169.53 g/plant). In the case of physiological and biological parameters also this level of nutrient application recorded maximum values for total chlorophyll content (1.528 mg stomatal frequency (2782.01 no cm"^), total soluble protein (20.25 mg g'), starch (13.88 mg g"'), reducing sugar (14.65 mg/g), total protein (15.25 mg g ) and fibre content (1.18 mg g"') and The highest number of root nodules per plant (45.26) and highest nutrient use efficiencies for N, P and K (1.013, 2.675, 0.293 g) were recorded under this treatment. In amaranthus, higher values were recorded in for number of leaves per plant (52.11), specific leaf area (316.20 cm^ g"'), dry root weight (2.13 g), dry shoot weight (4.34 g), root shoot ratio (0.64 g) and total dry matter production (10.47 g). Total chlorophyll content (1.542 mg g"'), stomatal frequency (705.64 no cm"^), total soluble protein (20.25 mg g"'), starch (3.29 mg g"'), reducing sugar (23.14 mg g"'). Calcium content (23.69 mg g'), Fe content (6.71 mg g"') and ascorbic acid content (43.51 mg/lOOg), under elevated CO2 condition. Though a C4 plant like amaranthus also responded to CO2 enrichment, extend of increase in growth and dry matter production was less compared to cowpea, which can be due to the mnate CO2 enrichment mechanism present in C4 systems. The fourth experiment was conducted to study the temperature and humidity interaction with CO2 enrichment. Potted plants of cowpea and amaranthus (variety Arun) were used for conducting the experiment. Plants were maintained at EC throughout the crop period as per POP recommendations of KAU. One set of plants were exposed to mist and the second set was maintained without exposure to mist. In cowpea, highest values were recorded by plants exposed to mist for number of leaves per plant (76.14), specific leaf area (471.07 cm^ g"'), dry root weight (21.74 g), dry shoot weight (72.46 g), root shoot ratio (0.302), dry matter production (104.2 g), single pod weight (15.93 g), number of pods per plant (18.75), number of seeds per pod (14.00), total yield (175.36 g/plant), RWC (96.48%), total chlorophyll content (1.651 mg g'^), stomatal frequency (2724.83 no cm"^), starch (13.29 mg g'^), reducing sugar (15.71 mg g"'), phenol (1.128 mg g"'). Free amino acid (6.398 mg g"'), SOD activity (3.56 g-Wnute-') and ascorbic acid content (9.36 mg/lOOg), Early flowering was induced in this set of plants. Parameters like transpiration rate (1.394 mmol water m-^ s"') total soluble protein (8.82 mg g"'), membrane integrity (43.92% leakage) recorded lower values under CO2 enriched treatments. In amaranthus, higher values were recorded under mist condition for number of leaves (48.51), specific leaf area (327.68 cm^ g"') dry root weight (2.160 g), dry shoot weight (6.74 g), root shoot ratio (0.517), dry matter production (8.90 g). RWC (95.38 %), Total chlorophyll content (1.382 mg g"'), stomatal frequency (694.02 no cm"^), starch (4.19 mg g'), reducing sugar (23.02 mg g"'), phenol (7.92 mg g"'), Free amino acid (1.536 mg g"'), SOD activity (2.44 g-'minute-') and ascorbic acid content (42.75mg/100g). Parameters like transpiration rate (12.36mmol water m-^ s ), total soluble protein (19.05 mg g') (25.40 %) and membrane integrity (% leakage) (6.47 % leakage) recorded lower values. Significant improvement in plant performance and increase in yield are seen under CO2 enrichment with mist exposure in the cases of cowpea and amaranthus The present study shows the existence of varietal variation in the crop responses under CO2 enrichment gives option for selection of varieties with better yield and quality under the changing climatic condition. Elevated CO2 concentration is found to be improve stress tolerance through better photosynthetic rate and activation of defence mechanism. Improved production technologies can be developed especially with mist facility with minimizing irrigation requirement. This can also be utilized for enhancement of antioxidant production which are economically valuable secondary metabolites. Exploitation of soils lacking sufficient nutrient and water can be done through the introduction of low cost CO2 enrichment methods. Since soil moisture and temperature are the primary determinants of nutrient availability and acquisition plant nutrition can strongly be influenced by global climate change. This necessitates site specific CO2 enrichment studies. The present study showed the existence of varietal variation in the crop responses under CO2 enrichment which gives option for selection of varieties with better yield and quality under the changing climatic scenario. Elevated CO2 concentration is found to improve the performance of plants grown under low soil moisture levels by improving the performance of photosynthetic machinery and by activating defence mechanisms. Based on this, improved high-tech agriculture production technologies with mist facility can be developed with minimum irrigation requirement which will ensure maximum water use efficiency. This also gives a possibility of utilizing the interactive effects of different cultivars, CO2 enrichment, and other abiotic factors for enhancing the production of antioxidants, many of which are economically valuable secondary metabolites. The present programme also opens up possibilities of quality improvement of agricultural products based on the interaction of elevated CO2 with factors like cultivars, growth stages, light, nutrient and abiotic stress factors. Intensification of cultivation and quality improvement are equally important to address the new challenges of global health because many of the economically important crops, when grown under field conditions at the elevated atmospheric C02were reported to have deleterious impacts on quality. The present study indicated the improved performance of cowpea under CO2 enrichment with additional nitrogen input. This points towards the changing nutrient requirement of crop plants under the current scenario of increasing CO2 concentration and suggests for bringing out modifications in the nutrient recommendations with additional nutrients, especially nitrogen. Exploitation of soils lacking sufficient nutrient and water also can be done through the introduction of low cost CO2 enrichment methods. Since soil moisture and temperature are the primary determinants of nutrient availability and acquisition, plant nutrition can strongly be influenced by global climate change. So this study also points to the requirement of site specific CO2 enrichment studies.