RESUMO
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.
RESUMO
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.