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Drought is one of the important problems that drastically affect sugarcane production in several countries. The objective of this research was to investigate the effects of early drought stress on physiological parameters and agronomic traits of six sugarcane genotypes under field conditions. The experiment was arranged in a split plot in a completely randomized block design with three replications. The main plot was represented by three different water regimes: field capacity (FC), ½FC and rain-fed (RF), whereas the subplot consisted of six sugarcane genotypes: KK3 (drought tolerant), Q117 (drought tolerant), LK92-11 (drought susceptible), Ths98-271 (S. spontaneum), KK08-214 (the F1 hybrid derived from S. spontaneum × S. officinarum) and E08-4-019 (the F1 hybrid derived from Erianthus sp. × S. officinarum). The six sugarcane genotypes were subjected to three irrigation treatments. The 45-day-old plants of all sugarcane genotypes were exposed to drought by withholding water for 72 days. Certain photosynthetic parameters were measured in the leaves of four-month-old plants. Certain cane yield parameters were measured in the 12-month-old plants. The results showed that early drought stress decreased the maximum quantum yield of PSII efficiency, net photosynthetic rate, transpiration rate and stomatal conductance. Drought stress significantly (p ≤ 0.01) decreased cane yield. The cane yield and sugar yield of KK3 were significantly (p ≤ 0.01) higher than those of the other genotypes. The wild-type sugarcane and the F1 hybrids derived from the wild and commercial sugarcane could maintain better photosynthetic performance while encountering early drought stress.

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Salt-induced changes in protein synthesis in leaf sheaths of the Thai rice cv. Leaung Anan were investigated using one-dimensional SDS-PAGE and two-dimensional PAGE (2DE). In SDS-PAGE, two protein bands (22 and 31 kDa) whose expression was specifically increased under salt stress were identified. Enhanced expression of these protein bands was consistently observed in plants grown under greenhouse conditions saline during different time of the year. In 2DE, at least thirteen different proteins were induced and ten different proteins were decreased by salt. Western blot analysis of the 31 kDa of rice seedlings of three cultivars: salt-tolerant Pokkali, moderately tolerant Leuang Anan, and salt-sensitive KDML 105, showed different expression patterns. The protein was strongly induced by salinity in leaf sheaths of treated tolerant Pokkali and Leuang Anan, compared to control plants. In contrast, its level in the sensitive KDML 105 remained unchanged with salt treatment. Moreover, rice cv. Leaung Anan showed higher expression of the 31 kDa protein than Pokkali. These results suggest that the 31 kDa polypeptide is a salt-induced protein in rice leaf sheaths.

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