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Open Access
Microencapsulation of Trichoderma viride for management of major soil borne fungal pathogens
(Department of Plant Physiology, College of Agriculture, Vellanikkara, 2020) Saleena, M; KAU; Reshmy, Vijayaraghavan
Trichoderma spp, one of the widely exploited biocontrol agents in the arena of crop disease management, are known for promoting growth and inducing abiotic stress tolerance in plants. However, direct application in the field limits their efficiency due to several adverse factors. Hence, they should be adequately formulated to escalate the efficacy in field application. Eventhough, a number of such formulations have been developed in the recent past, many of them are bulky in nature, having reduced shelf life with a high risk of contamination and desiccation. Thus, a study was conducted to develop a novel formulation of T. viride, with sodium alginate, a biodegradable polymer as the encapsulating carrier material. Evaluation of the effect of additive substances viz., mannitol (2%), trehalose (15 mM), polyvinyl pyrrolidone (1%), polyethylene glycol (0.25%), carboxymethyl cellulose (0.5%), liquid paraffin (1%) and tween 80 (0.5%) in eight combination on the shelf life of T. viride was carried out. After seven months of evaluation, a combination of trehalose, PVP, CMC and tween 80 outperformed the other treatments. Beads were prepared using 0.75, 1.5, 2.5, 3.0 and 3.5 per cent sodium alginate and 2.5, 3.0 and 3.5 per cent CaCl2 solution with and without additives. Without additives, no beads were formed at 0.75 and 1.5 per cent sodium alginate and spherical beads were formed at 2.5, 3.0 and 3.5 per cent. When additives were amalgamated, 0.75 and 1.5 per cent sodium alginate yielded spherical beads, while beads were not formed at 2.5, 3.0 and 3.5 per cent. Hence, the concentration of sodium alginate was standardized as 0.75 and 1.5 per cent. The impact of height of air column between the orifice of the separating funnel and the level of CaCl2 bath on the bead shape was evaluated at different heights where 2 and 4 cm yielded tailed beads while, rest of the heights yielded spherical beads. Hence, based on the shape of the bead, 8 - 12 cm was selected as the optimum height of air column. Previously standardized parameters along with 2.5, 3.0 and 3.5 per cent CaCl2 solution was adopted to prepare beads by employing ionotropic gelation and cross linking technique in 31 treatments. The beads were dried for 48 h at room temperature and stored in air tight containers. vii Properties like bead weight, diameter, yield and number of beads formed per ml sodium alginate solution was estimated. A maximum bead weight of 96.20 ± 1.8 mg and bead diameter of 2.42 ± 0.13 mm was recorded in control (T31-sodium alginate 2.5% and CaCl2 2.5%). Maximum per cent yield was documented in T19 (trehalose, PVP, CMC, tween 80, sodium alginate 1.5%, CaCl 2 2.5%) (69.09%) and a maximum of 26.91 beads were formed from each ml of sodium alginate in T9 while, it was 8.0 in control. Shelf life evaluation was carried out for six months, where T21 (trehalose, PVP, CMC, tween 80, sodium alginate 1.5%, CaCl2 3.5%) outperformed the other treatments even after six months hence, T21 was selected as the best treatment. Degree of contamination was estimated at 1, 3 and 6 months after preparation, where T1 - T6 and T19 - T30 remained free of contamination even after six months of preparation. Per cent of potentially infective beads were estimated where cent per cent germination was recorded at 72 h after incubation. Moisture content of the beads were assessed where the beads retained its intact shape at 48 h and therefore was selected as the optimum period of drying. Swelling behaviour of microbeads were estimated at pH 7.4 in phosphate buffer and at pH 1.0 in 0.1M HCl. A gradual increase in weight of beads at pH 7.4 confirmed the swelling behaviour while, reduction in weight at pH 1.0 revealed its shrinking nature. Time of gelation was standardized as 60 min as the bead weight declined until this time and attained stability after this time. The effect of pH on the selected bead (T21) was evaluated at pH 5.09 and 8.91 in soil under in vitro conditions where the release in former was sustained while a sudden release was observed in latter. Observations on biometric parameters, yield and the per cent disease incidence from pot culture experiments revealed that sodium alginate bead based formulation @ 5.0 g plant-1 performed superior to talc based and liquid formulations. The study on degradation revealed that the beads were biodegradable in nature. Thus, the present investigation succeeded in formulating T. viride using sodium alginate as the encapsulating carrier material, which would help to compensate the drawbacks associated with presently available formulations. However, the study should be complimented with multilocational trials to confirm its efficacy under field conditions.
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, T
Rice 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.
Open Access
Microencapsulation of Trichoderma viride for management of major soil borne fungal pathogens
(Department of Plant Physiology, College of Agriculture, Vellanikkara, 2020) Saleena, M; KAU; Reshmy, Vijayaraghavan
Trichoderma spp, one of the widely exploited biocontrol agents in the arena of crop disease management, are known for promoting growth and inducing abiotic stress tolerance in plants. However, direct application in the field limits their efficiency due to several adverse factors. Hence, they should be adequately formulated to escalate the efficacy in field application. Eventhough, a number of such formulations have been developed in the recent past, many of them are bulky in nature, having reduced shelf life with a high risk of contamination and desiccation. Thus, a study was conducted to develop a novel formulation of T. viride, with sodium alginate, a biodegradable polymer as the encapsulating carrier material. Evaluation of the effect of additive substances viz., mannitol (2%), trehalose (15 mM), polyvinyl pyrrolidone (1%), polyethylene glycol (0.25%), carboxymethyl cellulose (0.5%), liquid paraffin (1%) and tween 80 (0.5%) in eight combination on the shelf life of T. viride was carried out. After seven months of evaluation, a combination of trehalose, PVP, CMC and tween 80 outperformed the other treatments. Beads were prepared using 0.75, 1.5, 2.5, 3.0 and 3.5 per cent sodium alginate and 2.5, 3.0 and 3.5 per cent CaCl2 solution with and without additives. Without additives, no beads were formed at 0.75 and 1.5 per cent sodium alginate and spherical beads were formed at 2.5, 3.0 and 3.5 per cent. When additives were amalgamated, 0.75 and 1.5 per cent sodium alginate yielded spherical beads, while beads were not formed at 2.5, 3.0 and 3.5 per cent. Hence, the concentration of sodium alginate was standardized as 0.75 and 1.5 per cent. The impact of height of air column between the orifice of the separating funnel and the level of CaCl2 bath on the bead shape was evaluated at different heights where 2 and 4 cm yielded tailed beads while, rest of the heights yielded spherical beads. Hence, based on the shape of the bead, 8 - 12 cm was selected as the optimum height of air column. Previously standardized parameters along with 2.5, 3.0 and 3.5 per cent CaCl2 solution was adopted to prepare beads by employing ionotropic gelation and cross linking technique in 31 treatments. The beads were dried for 48 h at room temperature and stored in air tight containers. vii Properties like bead weight, diameter, yield and number of beads formed per ml sodium alginate solution was estimated. A maximum bead weight of 96.20 ± 1.8 mg and bead diameter of 2.42 ± 0.13 mm was recorded in control (T31-sodium alginate 2.5% and CaCl2 2.5%). Maximum per cent yield was documented in T19 (trehalose, PVP, CMC, tween 80, sodium alginate 1.5%, CaCl 2 2.5%) (69.09%) and a maximum of 26.91 beads were formed from each ml of sodium alginate in T9 while, it was 8.0 in control. Shelf life evaluation was carried out for six months, where T21 (trehalose, PVP, CMC, tween 80, sodium alginate 1.5%, CaCl2 3.5%) outperformed the other treatments even after six months hence, T21 was selected as the best treatment. Degree of contamination was estimated at 1, 3 and 6 months after preparation, where T1 - T6 and T19 - T30 remained free of contamination even after six months of preparation. Per cent of potentially infective beads were estimated where cent per cent germination was recorded at 72 h after incubation. Moisture content of the beads were assessed where the beads retained its intact shape at 48 h and therefore was selected as the optimum period of drying. Swelling behaviour of microbeads were estimated at pH 7.4 in phosphate buffer and at pH 1.0 in 0.1M HCl. A gradual increase in weight of beads at pH 7.4 confirmed the swelling behaviour while, reduction in weight at pH 1.0 revealed its shrinking nature. Time of gelation was standardized as 60 min as the bead weight declined until this time and attained stability after this time. The effect of pH on the selected bead (T21) was evaluated at pH 5.09 and 8.91 in soil under in vitro conditions where the release in former was sustained while a sudden release was observed in latter. Observations on biometric parameters, yield and the per cent disease incidence from pot culture experiments revealed that sodium alginate bead based formulation @ 5.0 g plant-1 performed superior to talc based and liquid formulations. The study on degradation revealed that the beads were biodegradable in nature. Thus, the present investigation succeeded in formulating T. viride using sodium alginate as the encapsulating carrier material, which would help to compensate the drawbacks associated with presently available formulations. However, the study should be complimented with multilocational trials to confirm its efficacy under field conditions.
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, T
Rice 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.
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, T
Gerbera (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
Open Access
Physiological and biochemical studies in cluster bean (Cyamopsis tetragonoloba (L.) Taub) as influenced by light and moisture stress
(Department Of Plant physiology, College Of Agriculture, Vellayani, 2020) Sreeraj; KAU; Viji, M M
The programme entitled “Physiological and biochemical studies in cluster bean [Cyamopsistetragonoloba(L.) Taub.] as influenced by light and moisture stress” was carried out at the Department of Plant Physiology, College of Agriculture, Vellayani, during 2019-2020. The objective of the programme was to study the light and moisture stress induced physiological and biochemical changes in cluster bean. A field study was carried out with the cluster bean variety ‘KAU Suruchi’ in Factorial Randomized Block Design (FRBD). It involved a combination of three levels of light stress (different shade levels) and three levels of moisture stress (different field capacity levels) which is inclusive of a control also, with four replications .The observations were taken at three different critical stages of the crop viz.vegetative stage, flowering stage and pod filling stage. Different shade levels were provided by using high-density polyethylene nets with differential light transmission to maintain 50 % and 25% shade and no shade net for open condition. Whereas for imposing moisture stress, three irrigation regimes based on gravimetric estimations were followed to maintain the field capacity levels of 100%, 75% and 50%.The treatment ( open condition + 100% field capacity) served as the control (T7) for the experiment. Different growth parameters such as plant height, number of primary branches per plant, root dry weight, shoot dry weight, root: shoot ratio, crop growth rate and relative growth rate were studied. It was found that only root dry weight and root: shoot ratio increased under combined light and moisture stress in comparison to control . However, plant height was found to increase under the treatments T1 (50% shade + 100% field capacity), T4 (25% shade + 100% field capacity), T5 (25% shade + 75% field capacity) and T6 (25% shade + 50% field capacity) compared to the control. The physiological parameters studied viz. transpiration rate and photosynthetic rate were found to decrease under the influence of both light and moisture stress conditions compared to the control. Among the biochemical parameters studied, total chlorophyll content was found to increase under the influence of both the stresses with the highest value (1.747 mg g-1, 1.947 mg g-1 and 2.141 mg g-1) across the three growth stages except that of treatment T9 (open + 50% field capacity).The chlorophyll ‘a’content was found to increase across all the treatments compared to the control. However chlorophyll ‘b’ content was found higher under shaded condition. But the chlorophyll a: b ratio was found to be higher only under open conditions. The total soluble protein content showed a decrease under the combined abiotic stresses. Overall it was observed that under the combined influence of light and moisture stress, physiological parameters such as plant height(T1,T4,T5 and T6), root weight and root: shoot ratio were up regulated whereas number of primary branches per plant, shoot weight, crop growth rate, relative growth rate, photosynthetic rate and transpiration rate were down regulated. As far as biochemical characters are concerned chlorophyll ‘a’, chlorophyll ‘b’ (T1 to T6), chlorophyll a: b ratio (T8 and T9) and total chlorophyll content (T1 to T8) improved, whereas the total soluble protein was found to decrease across all treatments compared to control. Considering the physiological, and biochemical characters, treatment T6 (25% shade + 50% field capacity) is favourable for the tolerance of cluster bean to the light and moisture stress, in view of the enhancement of plant height and chlorophyll content and the comparatively better performance than other stress combinations in comprehending the stress combination. However, the severest stress combination of treatment T3 (50% shade + 50% field capacity) enhanced the root: shoot ratio and lowered the transpiration rate the most, which is a positive aspect in terms of stress tolerance. In short, cluster bean is capable of tolerating light and moisture stress levels up to 50% shade and 50% field capacity respectively.
Open Access
Effect of high temperature on physiological, biochemical and yield parameters in tomato(Solanum lycopersicum L.)
(Department Of Plant physiology, College Of Agriculture, Vellayani, 2020) Amrutha, Vijayakumar; KAU; Beena, R
An experiment entitled “Effect of high temperature on physiological, biochemical and yield parameters in tomato (Solanum lycopersicum L.)” was conducted in the Department of Plant Physiology, College of Agriculture, Vellayani during Rabi 2019-2020 with the objective to study the effect of high temperature on physiological, biochemical, yield and quality parameters in tomato. Twenty two different tomato varieties were used for the study. The experiment was laid out in completely randomized design with two treatment levels i.e. control and high temperature stress (36+/-2oC) with three replications each. The high temperature stress was induced from flower initiation to maturity stage by keeping the pots in a temperature controlled green house facility for 45 days. Phenological, physiological, biochemical parameters were taken at flowering stage. Also quality parameters and yield parameters were taken at harvesting stage. All the tomato genotypes under heat stress showed delayed flowering and fruiting. Delay in flowering was found to vary between the varieties. Kashi Vishesh showed minimum delay in first flowering (10-12 days) than that of control whereas, Pusa Rohini showed maximum delay in flowering (25-30 days) than that of the control plants. Kashi Vishesh showed less delay in first fruiting (8-12 days) than that of control whereas, genotypes like Arka Rakshak, PKM-1, Pusa Rohini showed maximum delay (30-35 days) in fruiting under stress conditions. Under high temperature condition, Arka Sourabh showed the highest exerted stigma length and there is significant variation for flower burning and flower drop. A decrease in Membrane Stability Index (MSI) was observed for varieties on 15th day after stress induction and further reduction for 25th day after stress induction when compared to control plants. Under heat stress conditions, Nandi (51.8%) and Arka Rakshak (25.13%) showed maximum and minimum MSI respectively. The percentage reduction in MSI was highest in Pusa Ruby (52%) and lowest in IIHR-2200 (11%). Under high temperature conditions pollen viability reduced significantly for all varieties with maximum viability for Nandi (87.38%) and minimum for Arka Vikas (36.31%). Similar results were obtained for physiological parameters like total chlorophyll content (mg g-1 fresh weight), photosynthetic rate (A) μ CO2 moles m-2 s-1), transpiration rate (E) (mmol H2O m-2 sec-1), stomatal conductance (Gs) (mmol H2O m-2 sec-1) and chlorophyll fluorescence (CF-Fv / Fm). The percentage reduction in photosynthetic rate under high temperature condition was highest in Palam Pride (30%) and minimum for Manulakshmi (9%). The percent reduction in transpiration rate was maximum for Arka Sourabh (67%) and minimum for Kashi Vishesh (12%). Significant genotypic differences for starch content and soluble sugar content were observed in tomato plants under high temperature. Among the genotypes, Vaibhav (312.97 mg g-1 fresh weight) recorded the maximum starch accumulation while the minimum starch content was recorded in Arka Vikas (209.70 mg g-1 fresh weight) under control conditions. Under heat stress condition, the highest starch content was observed in Anagha (235.67 mg g-1 fresh weight), while the lowest was observed in Arka Sourabh (84.37 mg g-1 fresh weight). The percent decrease in soluble sugar content was more in Arka Rakshak (31.2%) and less in IIHR-2200 (3%) under high temperature condition. Titrable acidity (TA) and total soluble solids (TSS) of tomato fruits were highest in concentration under high temperature conditions compared to low temperature regimes. The percent increase in titrable acidity under heat stress was highest for Arka Alok (27%) and minimum for Pusa Rohini (2%). Highest TSS was recorded for Arka Samrat (5.72%) and lowest for IC-45 (2.32%) under control ambient condition. But under high temperature conditions highest TSS was recorded for Kashi Vishesh (6.23%) and lowest for IC-45 (2.57%). The lycopene content decreased with rise in temperature and the ambient condition recorded the highest lycopene content in fruits. The percent reduction in lycopene content under heat stress conditions was maximum for IIHR-2200 (52%) and minimum for Kashi Vishesh (3%). The yield attributes viz., number of fruits/plant, fruit set %, average fruit weight (g), yield per plant (g /plant) were significantly lower for varieties like Arka Saurabh, Arka Rakshak and Pusa Rohini. Under heat stress conditions only those genotypes that are tolerant as well as moderately tolerant, namely Nandi, Anagha, Akshaya, IIHR-2200, Vellayani Vijay, Kashi Vishesh, Arka Abha, Arka Alok, Vaibhav, Manuprabha, Manulakshmi, IC-45 and IIHR-26372 produced higher fruit yield per plant. But the varieties like Arka Saurabh, Arka Rakshak, PKM-1, Sakthi, Palam Pride, Arka Samrat recorded the maximum percent reduction in yield per plant (99%) and the minimum was recorded in Kashi Vishesh (69%). In polyhouse conditions, all the genotypes showed an increment in the plant height and total dry weight because of the shaded environment, high temperature and enhanced CO2 (570 ppm) conditions inside. With respect to yield and physiological data the varieties sharing similar characteristics can be classified under three categories viz, tolerant varieties, moderately tolerant and susceptible varieties. Tolerant genotypes (Nandi, Kashi Vishesh, Vellayani Vijay) exhibited similar characteristics like yield (10-30 g-1 plant), MSI (60-70 %), PV (50-70%), starch content (190-200 mg g-1 fresh weight), A (17-22 μmol CO2 m-2 sec-1), Gs (47-68 mmol H2O m-2sec-1), CF (Fv / Fm) (0.6-0.7). Moderately tolerant varieties (Akshaya, Manuprabha, IIHR-2200, Vaibhav) showed similar characteristics like yield (5-15 g-1 plant), MSI (40-50 %), PV (45-50 %), starch content (200 mg g-1 fresh weight), A (17-19 μmol CO2 m-2 sec-1), Gs (55-65 mmol H2O m-2sec-1), CF(Fv / Fm) (0.6-0.7) and susceptible varieties (Arka Vikas, Pusa Rohini, Arka Sourabh, Arka Rakshak) showed similar features like yield (0.5-5 g-1 plant), MSI (25-40 %), PV (44-45 %), starch content (90-110 mg g-1 fresh weight), A (13-16 μmol CO2 m-2 sec-1), Gs (30-37 mmol H2O m- 2sec-1) and CF (0.4-0.5). The correlation analysis revealed that under heat stress conditions yield showed positive and significant correlation with MSI, photosynthetic rate, stomatal conductance, starch content, soluble sugar content, CF(Fv / Fm), pollen viability, total chlorophyll content, number of fruits per plant, fruit set %, average fruit weight and negatively correlated with intensity of flower drop. Hence this study has importance in identifying genotypes that possesses important physiological traits to increase the thermo-tolerance, so that they could give moderately higher yield even under high temperature.
Open Access
Influence of elevated CO2 on zinc dynamics in rice (Oryza Sativa L.)
(Department of Plant Physiology, College of Agriculture, Vellayani, 2020) Ramireddy, Bhavana; KAU; Manju, R V
The present programme “Influence of elevated CO 2 on zinc dynamics in rice (Oryza sativa L.)” was undertaken in the Department of Plant Physiology, College of Agriculture, Vellayani during 2018-2020 with the objective of assessing the impact of elevated CO2 on growth, development and nutritional quality of rice in relation to modifications in Zn dynamics. The extent of variation in growth, physiological, biochemical parameters and parameters related to Zn dynamics were assessed in two rice genotypes, Uma (MO16) and Njavara-golden yellow. Plants were maintained under three CO2 conditions i.e., OTC (Open Top Chamber) (500 ppm), Polyhouse (420 ppm) and open field condition (390 ppm) with four zinc enrichment treatments (D1- Foliar spray (ZnSO4 0.5% at panicle initiation and grain filling stage); D2-AMF (3g of AMF inoculum /cavity of protrays); D3-Seed treatment: seed priming with 6.4% ZnSO4 for 36 hrs; D4-control) with the aim to improve the zinc status of rice plants. The experiments were laid out in CRD with 24 treatment combinations and three replications. The study indicated that upon exposure to 500ppm CO2, highest values were recorded in plant height, no. of tillers, root weight and straw yield in the case of both varieties. The treatment with 0.5% ZnSO4 foliar spray (D1) recorded highest plant height (102cm), no. of tillers (34) and straw yield, (35g/plant) in Uma and in Njavara the same treatment resulted in highest plant height (130cm), no. of tillers (32) and straw yield (46.8g/plant). AMF treatment (D2) has recorded highest root weight both in Uma (26.7g/plant) and Njavara (20.4g/plant). The no. of days to 50% flowering was increased under OTC (85 days in Uma and 71 days in Njavara) and Polyhouse (80 days in Uma 69 days in Njavara) as against 72 days in Uma and 61days in Njavara under open field condition. Physiological and biochemical parameters recorded at active tillering and grain filling stage had shown that OTC condition resulted in highest total chlorophyll content (2.33 mg g-1 fresh weight), photosynthetic rate (27 µmol CO 2 m -2s-1) and total reducing sugars (1.9 mg g-1) at active tillering stage. The same trend was observed in grain filling stage also but to a lesser extent in total chlorophyll content (1.805 mg g-1 fresh weight) and photosynthetic rate (17.6 µmol CO 2 m -2s-1) whereas the total reducing sugars (6.3 mg g-1) was increased to a greater extent. However the photosynthetic rate and total chlorophyll content were decreased at grain filling stage in all the three CO2 conditions. Lowest total soluble protein was recorded under OTC in active tillering stage (0.8 mg g-1) and grain filling stage (7.1 mg g-1). All the Zinc treatments had significant influence on all the above parameters and foliar spray with 0.5% ZnSO4 resulted in maximum enhancement. The transpiration rate and stomatal conductance which was decreased under eCO2 did not show significant difference upon application of Zn treatments in both the varieties. Yield attributes and Zn content in grain and bran could not be recorded as there was no grain development in plants under OTC due to high temperature. The parameters related to zinc dynamics were analyzed in leaf and shoot under all the conditions. Decreasing levels of zinc in leaf and shoot with increasing levels of CO2 was evident in both the varieties of rice in the present study in untreated plants. Though all the zinc treatments were having positive influence on Zinc status, foliar application of 0.5% ZnSO4 was found to be the most effective one followed by seed treatment and AMF. The zinc content in leaf was highest in D1 with 25.8 μg g-1 in Uma and 26.1μg g-1 in Njavara. Similarly, the zinc content in shoot was also recorded highest in D1 with 25.4 μg g-1 in Uma and 26 μg g-1 in Njavara followed by D3 and D2. In the present study, increasing concentration of CO2 was found to enhance growth and development in rice variety Uma and Njavara by inducing increased photosynthetic rate, chlorophyll and reducing sugars content but at the same time it had a negative influence on Zinc content leaf and shoot tissue which was decreased due to the accumulation of more no. of carbohydrates which has diluted the Zn concentration in the leaf and shoot tissue in the untreated plants. Supplement of zinc through different treatments has elevated the zinc content in the leaf and shoot tissue in all the three different CO2 conditions. These results offer a small slice of the broad implications for the impact of higher CO2 on nutrition and health. Taken together, CO2 induced nutritional declines could produce a major headwind on progress towards alleviating malnutrition and deserves attention and concerted action. The information generated will help farmers to raise quality produce with the help of low cost technologies, to make paddy cultivation more profitable and can also be an answer to the serious health crisis and malnutrition faced globally in this changing climatic scenario.

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