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Water stress adversely affects the photosynthetic apparatus and pigment composition in plants, leading to reduced yields and compromised plant health. Zinc (Zn) foliar spray in nano form presents a potential solution to ameliorate water deficit stress. We attempt here a detailed dissection of electron transport in Photosystem II (PSII) through studies on chlorophyll a fast fluorescence kinetics and non-photochemical quenching (NPQ) and pigment dynamics in response to water stress. We also investigated the possible changes in these processes and the regulation of it by Zn Nano and Zn Ethylenediaminetetraacetic acid (EDTA) foliar sprays that may lead to amelioration of stress. Our results indicated that water stress created a ''traffic jam'' like situation in the electron transport system of Photosystem II, leading to decreased photosynthetic efficiency. Treatments with water deficit stress + Zn Nano (particle size < 90 nm) spray with Zn concentration at 20 mg L−1 and water deficit stress + Zn EDTA spray (solid material size ∼ 100 µm) with Zn concentration at 240 mg L−1 effectively ameliorated water deficit stress by its action on flux ratio parameters viz., quantum yield for electron transport (φE0), probability of electron transport beyond QA (ψ0) and quantum yield of electron transport from QA⁻ to PS1 end electron acceptors (ϕR0) and also the specific fluxes and phenomenological fluxes. These treatments positively influenced chlorophyll content, and xanthophyll components, including violaxanthin, antheraxanthin, and zeaxanthin, and reduced NPQ and the de expoxidation state. Higher concentrations of Zn Nano foliar spray (water stress + Zn Nano spray Zn @ 30 mg L⁻¹) did not ameliorate water deficit stress as effectively as the lower concentrations, although this higher concentration was not in any way toxic. This lack of stress amelioration at higher concentrations of Zn Nano spray may be due to physiological limitations of elemental zinc action within the plant. Our findings suggest that Zn foliar sprays in Nano and EDTA form at optimum concentrations can significantly improve plant resilience to water stress.

Abstract The rising temperatures and levels of carbon dioxide in the atmosphere are anticipated to have a significant impact on the productivity of agricultural crops. Although, the individual effects of elevated CO2 and temperature have been extensively studied in C3 and C4 crops, there remains a scarcity of research investigating their interactive effects specifically on maize hybrids. The impact of elevated temperature and its interaction with elevated CO2 on phenology, physiology, biomass, and grain yield of maize hybrids was assessed in a field experiment using Free Air Temperature Elevation (FATE) facility. The results showed that elevated temperature (eT) increased the anthesis silking interval (ASI), while the presence of elevated CO2 along with elevated temperature (eT + eCO2) mitigated this effect. The differential expression were observed between hybrids depending on their genetic potential. Furthermore, the net photosynthetic rate (Anet), stomatal conductance (gs), and transpiration rate (Tr) of hybrids decreased under elevated temperature but eT + eCO2 condition helped in reverting its impact to some extent. In term of leaf composition, the highest level of total soluble sugars (TSS) and starch was observed under eT + eCO2 conditions, possibly due to improved Anet in the presence of elevated eCO2. The negative impact of eT was also evident through increased proline and MDA content, but eT + eCO2 ameliorated the adverse effect of eT. The biomass and grain yield also responded similarly, among the hybrids 900M GOLD recorded superior performance for grain yield at eT condition exceeding 35 °C. On the other hand, DHM117 experienced a significant reduction in grain yield under eT, but performed better under eT + eCO2 due to its improved physiological response to eCO2. The study indicated that elevated levels of carbon dioxide can actually mitigate the detrimental effects of elevated temperature on maize crop. This positive impact on maize crop can be attributed to an enhanced physiological performance in the presence of eCO2 which enables the plants to maintain satisfactory yield levels despite the challenging environmental conditions.

Transpiration Efficiency (TE), the biomass produced per kilogram of water transpired is an ideal parameter for measuring genetic variation in crop water use efficiency. Assessing the genetic diversity and variability in maize for this character will help us to understand the most efficient genotypes for water use. Studies on 89 maize genotypes for two years using six characters revealed significant differences among the genotypes and wide range of variation for all the characters. High variability was observed for total biomass, seed yield and TE-seed. High heritability and genetic advance as per cent of mean was observed for all the characters except water transpired. Eighty nine genotypes were grouped into 10 clusters and total biomass contributed maximum towards genetic divergence. TE seed was positively and significantly correlated with all the characters studied except water transpired. As there is a lot of variability present in the maize genotypes and the desirable characters reported high coefficients of variability, heritability, genetic advance and positively high correlation among the characters, the chance of selecting superior genotypes are more. Moreover, crossing between different clusters of clusters will enhance the chance of transgressive segregants. Maize genotypes Z 32-87, NSJ-176, DTL-2, Z101-68, HKI-1040-4, NSJ-189, LM-16, HKI-1025, NSJ-2011-26, NSJ-2011-37, DTL-3, DTL 4-1 HKI-1332, Z-60-72 and PSRJ-13038 were found to be superior for TE biomass and TE seed.

Forty two F1 hybrids of blackgram were produced in line x tester mode with fourteen lines and three testers. The F1 hybrids along with parental lines were raised during kharif, rabi and summer 2013-14 to assess the heterosis and combining ability for seed yield and yield attributes over different environments. The pooled ANOVA revealed significant variability for seed yield, number of branches, pods, clusters, 100 seed weight, fodder biomass and harvest index due to crosses, environment, environment × crosses, while significant variability for environment × line × tester effect for all characters except for number of branches. Among 42 hybrids, three hybrids tested IC 587753 × PU-19, IC 436720 × PU-19, IC 436652 × LBG-20 exhibited significant and positive heterosis over mid, better and standard parent for seed yield, as well as significant specific combining ability. Hence these hybrids of this important pulse crop can be used for seed yield improvement through recurrent selection. Two lines viz., IC 587753 and IC 519805 identified as good general combiners for seed yield and can serve as parental lines in crop improvement programs.

Four groundnut (Arachis hypogaea L.) genotypes- Narayani, Dharani, K-6 and K-9 were assessed for growth and yield responses at elevated temperature of 3.0 ± 0.5°C above ambient canopy temperature (eT) and its interaction with elevated CO of 550 ± 50ppm (eT+eCO ) under Free Air 2 2 Temperature Elevation (FATE) facility. The study revealed that eT significantly decreased photosynthetic rate (A ) of all groundnut genotypes whereas eT+eCO condition ameliorated the ill effects of eT. The net 2 impact of eT on A was higher than transpiration rate (Tr) and this reflected in decreased WUE with all net genotypes. WUE improved significantly at eT+eCO with increased A and decreased Tr. Increase in 2 net canopy temperature (eT) resulted decreased relative water content (RWC), cell membrane stability and increased osmotic potential, Malondialdehyde (MDA) content and accumulation of proline. Elevated CO 2 along with eT (eT+eCO ) facilitated these parameters to recover to that of ambient controls, revealing the 2 ameliorative effect of eCO . Similar responses were recorded for biomass and yield parameters. Among 2 the selected groundnut genotypes, superior performance for seed yield at high temperature of >40°C by K-9 was due to ability to maintain better reproductive capacity and Dharani was responsive to elevated CO even at high temperature, indicating the genotypic variability.

A field experiment was conducted with maize (Zea mays L.) hybrid DHM-117 under elevated temperature and moisture deficit stress to assess the phenology, physiology, biomass and yield responses. The elevated canopy temperature (ET) was maintained as 3°C above ambient canopy temperature (AT) in Free Air Temperature Elevation (FATE) facility and water deficit stress (WD) was imposed at initiation of tasseling stage in an open plot experiment to assess the impact of these two abiotic stresses. As compared with ambient control, the phenology of flowering with the ET was early as 3 days for anthesis, 1 day for silking and this increased 4 days for anthesis silking interval (ASI), while with WD, anthesis was delayed by 2 days, silking by 3 days and ASI increased by 3 days. It was observed that both ET and WD significantly decreased photosynthetic rate (32%, 24%), stomatal conductance (45%, 28%), transpiration rate (36%, 44%) while increased WUE (6%, 38%). It is interesting to record that there was reduction in total biomass (11%, 13%) especially reproductive biomass (44%, 31%) with both ET and WD while vegetative biomass was improved (27%, 8%) revealing that reproductive components are effected with these abiotic stresses thereby decreased HI (42%, 36%). The impact of ET was more on seed set than seed filling as the reduction in test weight (8%) was higher than at WD (4%).

Sunflower Hybrid (KBSH-1) was cultivated in Open Top Chambers (OTCs) at ambient (380 ppm) and elevated CO2 (550 and 700ppm) conditions. Biomass accumulation in root, stem, head and seed was significantly greater at elevated CO2 (550 ppm and 700ppm) compared with ambient (380 ppm).The improvement in total biomass with 550 and 700 ppm CO2was 18.7 per cent and 40.5 percent and seed yield was 21.0 per cent and 45.9 per cent respectively compared to ambient. The positive growth response to increased atmospheric CO2 resulted in N and C concentrations. Although elevated CO2 levels tended to lower N concentration in some plant parts compared to ambient, elevated CO2 enhanced total N accumulation in each plant component via an increase in biomass.Elevated CO2 decreased the N per cent compared to ambient in seed meal, leaf and stem. At the recommended dose of nutrients, the total N uptake was high in plants grown at 700 ppm (1.25 g per plant), followed by 550 ppm (1.11g per plant) and ambient (0.96 11 g per plant). At the recommended dose of nutrients, physiological N use efficiency (PE) and grain N use efficiency (NUEg) was also high in plants grown at elevated CO2 in OTCs and nitrogen harvest index (NHI) was similar for ambient (70.3%) and elevated CO2 conditions (70.4 and 70.2 per cent at 550 ppm and 700 ppm).The total carbon accumulation was high in plants grown at 700 ppm, followed by 550 ppm and ambient.The C/N ratio of plants was high at elevated CO2 conditions being 21.2, 20.0 and 19.0 at 700, 550ppm and ambient control respectively.

Sunflower (Helianthus annuus L.) and maize (Zea mays L.) were chosen as C3 and C4 crop plants and assessed for the impact of enhanced CO2 (700 ppm) and its interaction with drought stress in open top chambers (OTCs). The ameliorative effect of higher CO2 concentration (eCO2) under drought stress was quantified. It is interesting to note that the C3 crop responded significantly and positively with eCO2 under both well-watered and drought stress treatments for root: shoot ratio while C4 crop showed a better response only with the drought stress environment. Root volume showed a positive significant response with CO2 concentration enhanced over ambient level and the increment in root volume was 146% and 340% in sunflower and maize crops, respectively. The leaf water potential, stomatal conductance and transpiration showed a decreasing trend in both the crops with drought stress and eCO2 showed an ameliorative effect leading to higher Pn rates in sunflower crop under drought stress treatment. The findings reveal that improvement of root traits is worth attempting for the future crop behavioral responses under eCO2 and drought stress environments. The study confirmed the beneficial effect of eCO2 in maize and sunflower by ameliorating the adverse affects of drought stress.

Growth and yield responses of castor bean (Ricinus communis L.) to two elevated CO2 levels (550 and 700 ppm) were evaluated up to the maturity of first order spikes in open top chambers (OTCs). The growth characteristics - root and shoot lengths, root volume, root:shoot ratios, leaf area, dry weights of different plant parts, leaf area duration and crop growth rate increased with 550 and 700 ppm of CO2 levels compared with ambient control. The spike length, pod and seed yield of first order spikes increased under enhanced CO2 levels over ambient control. Elevated CO2 levels significantly increased the total biomass and yield of castor bean, however enhanced CO2 levels per se did not changed the content and quality of the castor oil. A positive response of castor bean to increased CO2 concentrations is a good indication for its future existence in potentially changed climatic conditions.

The response of blackgram (Vigna mungo L. Hepper) to two levels of elevated carbon dioxide (550 and 700 ppm) in terms of growth and yield was investigated and compared with ambient CO2 level (365 ppm) using open-top chambers. The growth parameters viz., length and weight of root and shoot, root:shoot ratio, leaf area and weight significantly increased at 700 ppm CO2 when compared with 550 ppm. The percentage increase in total biomass at 700 and 550 ppm CO2 was 65.4% and 39%, respectively compared to the ambient (chamber) control. The increase in total seed yield at 700 ppm (129%) was due to an increase in number of pods per plant and 100 seed weight, whereas at 550 ppm (88.7%) it was due to an increased number of pods/plant and seeds/pod. The results indicate variable responsive effects at different levels of CO2 emphasizing the pertinence of research on elevated CO2 in various agroecological inhabitations all over the world. The indication of higher responses for root and leaf at initial growth stages at the higher elevated level of CO2 (700 ppm), which leads to better root establishment, achieving early photosynthetic efficiency and also better biomass production, and its improved partitioning can be reckoned as a positive aspect of increasing concentrations of CO2 in atmosphere. The harvest index increased significantly to 35.7 and 38.4% at 550 and 700 ppm, respectively; it is a very important phenomenon in pulses for breaking the yield barrier.

An attempt was made to understand the interactive effect of the elevated CO2 and moisture stress on germination and initial growth responses of blackgarm (Vigna mungo L. Hepper). Four open top chambers (OTCs) were used for different conditions: irrigated with ambient CO2 (365 ppm), irrigated with elevated CO2 (600 ppm), moisture stress with ambient CO2 and moisture stress with elevated CO2. The percentage of germination, germination speed, emergence index, and vigor index were measured on the 5th and 6th day after sowing (DAS). Plants were harvested at different time intervals, i.e. on 7, 14, 21 and 28 DAS; leaf area and dry weights of the seedlings were recorded. It was observed that moisture stress in general reduced the germination in all the conditions and affected seedling growth of blackgram. Germination percentage, emergence index, germination speed and vigor index were increased with elevated CO2 under both irrigated and moisture stress conditions. Plants grown with elevated CO2 were taller and attained a greater leaf area along with more biomass than ambient CO2 levels under irrigated and moisture stress conditions at all time intervals. The increase in the germination, larger leaf area and dry matter of root, shoot and leaf proved that CO2 enrichment of the atmosphere will be beneficial for the crops for better establishment and greater productivity.

A study was conducted with two important rainfed food crops viz., sorghum (Sorghum bicolor L. Moench.) and blackgram (Vigna mungo L. Happer) and two oil seed crops viz., sunflower (Helianthus annuus L.) and groundnut (Arachis hypogaea L.) under two conditions viz., elevated CO2 (600 ppm) and ambient CO2 (365 ppm) in open top chambers (OTCs). The observations were recorded at the vegetative stage at 7, 14, 21 and 30 days after sowing (DAS). The results showed significant differences between crops, conditions and time intervals, as well as the single and double order interactions for all the characters studied viz., total dry weight, stem dry weight, root dry weight, leaf dry weight, shoot length, root length and leaf area. Total dry weight and its components viz., stem dry weight, root dry weight and leaf dry weight along with leaf area showed a significant increase under enhanced CO2 conditions. Among the four crops studied the overall results showed the highest response to elevated CO2 by blackgram while the lowest response by sorghum.

Sunflower plants (C3) transpired more water than pearl millet (C4) from seedling to maturity under ambient conditions. The transpiration (water use) at elevated CO2 was lesser for pearl millet and higher for sunflower compared to ambient. Elevated atmospheric CO2 increased TE more in pearl millet (21.9%) than in sunflower (10.5%) and decreased the TR or water transpired to produce dry mass by 18.1% in pearl millet and 9.7% in sunflower compared to ambient. As the CO2 content of the air continues to rise, both sunflower (C3) and pearl millet (C4) agriculture crops will respond favorably by exhibiting increases in TE.

An efficient and rapid regeneration protocol was developed using shoot apices from germinating seedlings of two cultivars of sorghum, SPV-462 and M35-1, as explants. A vertical slit given from the base of each dissected apex enhanced the efficiency of callusing response by two fold. MS medium containing 0.5 mg dm−3 each of 2,4-D and kinetin was most effective in producing friable and embryogenic calli. Scanning electron microscopy of these calli detected somatic embryogenesis. Calli thus induced gave rise to approximately 42 green shoots per callus in both the genotypes when transferred to regeneration medium containing 1.5 mg dm−3 kinetin. [ABSTRACT FROM AUTHOR]

Three pigeonpea (Cajanus cajan L. Millsp.) genotypes- GT-1, AKP-1 and PRG-158 with varying crop duration, growth habit and flowering pattern were evaluated for variability in their response for drought stress. Drought stress was imposed at initiation of flowering and the observations on biomass and seed yield parameters were recorded at harvest. The magnitude of response of individual component to drought stress was found to be genotype specific. Drought stress significantly decreased photosynthetic rate (PN), transpiration rate (Tr) and relative water content (RWC) in all the genotypes, however the magnitude of reduction differed with genotype. With drought stress, the reduction of PN was highest in GT-1 while reduction in Tr was highest in PRG-158. The genotype AKP-1, accumulated significantly higher concentrations of osmotic solutes especially proline under water deficit stress, this facilitated it to maintain higher relative water content (RWC) and lower malondialdehyde (MDA) content as compared to other genotypes. Drought stress also impacted biomass production and their partitioning to vegetative and reproductive components at harvest. There was significant variability between the genotypes for seed yield under drought stress while it was non-significant under well-watered condition. Drought stress enhanced flower drop and decreased flower to pod conversion resulting in reduced pod number and seed number in PRG-158 and GT-1. The genotype AKP-1 recorded superior performance for seed yield under stress environment due to its ability in maintaining pod and seed number as well as improved test weight (100 seed weight). Under drought stress, significant positive association of seed yield with proline, seed number, pod number and test weight clearly indicating their role in drought tolerance.