Global warming has increased the temperature significantly over a large extent both spatially and temporally. The threat of heat stress during the germination and seedling establishment stages in the wheat crop is now more prevalent than ever before. The present experiment assessed the effect of elevated temperature on the germination and early seedling growth of wheat genotypes. The seeds were sown under four temperatures, viz., 20 °C, 25 °C, 30 °C and 35 °C; the germination, seedling vigor and enzyme activities in 8-day-old seedlings were assessed. The temperature significantly influenced germination and early seedling growth. The germination percentage at 20 and 25 °C was statistically on par with and higher than at 30 and 35 °C. The seedling vigor parameters were maximum at 25 °C and showed a reduction at higher temperatures. Genotypic differences were observed for early heat stress as the genotypes WH 730, WH 1123 and HD 2967 showed tolerance towards heat stress during germination, whereas the genotypes PBW 725 and WH 1105 were susceptible. Antioxidant enzyme activities in seedlings increased with the rise in temperature. Catalase, peroxidase and superoxide dismutase enzymes showed increased activities at higher temperature levels.
In the present era of climate change and global warming, high temperatures have increased considerably, posing a threat to plant life. Heat stress affects the biochemistry, physiology and molecular makeup of the plant by altering the key processes, i.e., photosynthesis, respiration and reproduction which reduces its growth and development. There is a dire need to manage this problem sustainably for plant conservation as well as the food security of the human population. Use of phytohormones to induce thermotolerance in plants can be a sustainable way to fight the adversities of heat stress. Phytohormone-induced thermotolerance proves to be a compelling approach to sustainably relieve the damaging effects of heat stress on plants. Salicylic acid (SA) is an essential molecule in biotic and abiotic defense response signal transduction pathways. When supplied externally, it imparts heat stress tolerance to the plants by different means, viz., increased Heat Shock Proteins (HSP) production, Reactive oxygen species (ROS) scavenging, protection of the reproductive system and enhancing photosynthetic efficiency. The effect of SA on plants is highly dependent on the concentration applied, plant species, plant age, type of tissues treated, and duration of the treatment. The present review paper summarizes the mechanism of thermotolerance induced by salicylic acid in plants under heat stress conditions. It includes the regulatory effects of SA on heat shock proteins, antioxidant metabolism, and maintenance of Ca 2+ homeostasis under heat stress. This review combines the studies conducted to elucidate the role of SA in the modulation of different mechanisms which lead to heat stress tolerance in plants. It discusses the mechanism of SA in protecting the photosynthetic machinery and reproductive system during high-temperature stress.
Seed priming is a simple and cost effective method to obtain a better plant stand under diverse environmental conditions. The current study was designed to determine the optimal priming duration and water volume for wheat seed. For this experiment, three wheat genotypes with distinct genetic and adaptive backgrounds were chosen. Seeds of each genotype were hydroprimed for 7 durations, i.e. 1, 2, 4, 8, 12, 16, and 20 hours, in three different water volumes, i.e. half, equal, and double volume with respect to seed weight and then surface dried for 1 hour. The control was unprimed (dry) seed. The germination characteristics and seedling vigour potential of hydroprimed seeds were evaluated in the lab by recording several parameters such as germination percentage and speed, seedling growth, and vigour indices at two different temperature levels. The results showed that optimal duration for hydropriming of wheat seed is 12 hours with an equal volume with respect to original seed weight, closely followed by 8 hours with double volume. Reduction in seed performance was observed at 16 and 20 hours priming particularly at double volume treatment. Effect of temperature on seed germination showed improvement in seedling vigour at 25°C when compared to 20°C, although effect on germination percentage was non-significant. Volume of water and priming duration showed significant interactive effects demonstrating that a higher volume can give equivalent results at a shorter duration and vice versa. Another experiment was also conducted to compare the on-farm priming (surface dried seed) with conventional priming (seed re-dried to original moisture) taking 3 potential durations i.e. 8, 12 and 16 hours. Results revealed that both priming methods were statistically at par in terms of germination percentage, while, surface drying resulted in better seedling vigour and speed of germination.
Seed priming is a simple and cost effective method to obtain a better plant stand under diverse environmental conditions. The current study was designed to determine the optimal priming duration and water volume for wheat seed. For this experiment, three wheat genotypes with distinct genetic and adaptive backgrounds were chosen. Seeds of each genotype were hydroprimed for 7 durations, i.e. 1, 2, 4, 8, 12, 16, and 20 hours, in three different water volumes, i.e. half, equal, and double volume with respect to seed weight. The control was unprimed (dry) seed. The germination characteristics and seedling vigour potential of hydroprimed seeds were evaluated in the lab by recording several parameters such as germination percentage and speed, seedling growth, and vigour indices at two different temperature levels. The results showed that optimal duration for hydropriming of wheat seed is 12 hours with an equal volume with respect to original seed weight, closely followed by 8 hours with double volume. Reduction in seed performance was observed at 16 and 20 hours priming particularly at double volume treatment. Effect of temperature on seed germination showed improvement in seedling vigour at 25°C when compared to 20°C, although germination percentage decreased slightly. Volume of water and priming duration showed significant interactive effects demonstrating that a higher volume can give equivalent results at a shorter duration and vice versa.
Thirty four pearl millet restorer lines were evaluated on the basis of nine seed vigour traits and molecular analysis was done with 55 SSRs to study the genetic divergence among them. Cluster analysis based on seed vigour parameters revealed the considerable amount of variability and all genotypes were divided into six clusters. Furthermore, a set of 39 SSRs, selected after initial screening of 55, amplified 226 alleles with a mean of 5.84 alleles per locus. The highest polymorphic information content (PIC) value obtained was for PSMP 2084 (0.88) with a range of 0 to 0.88 and average PIC of 0.558. Neighbor joining tree based on molecular data differentiated all the genotypes into two major groups. The grouping based on both approaches can help breeders to use the studied material in further breeding for improvement of germination potential and early seedling vigour of pearl millet.
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