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VARIATIONS IN ADAPTATION STRATEGIES OF WHEAT CULTIVAR REPLACEMENTS UNDER SHORT-TERM OSMOTIC STRESS

JIAKUN YAN^1,3, NINGNING ZHANG^1,3, NAN WANG^1,2, YUPING LI², SUIQI ZHANG^1,2* AND SHIWEN WANG^1,2

Abstract: Wheat (Tritium aestival L.) production has increased substantially with wheat cultivar replacements, but little is known about how different-year released wheat cultivars maintain whole-plant water balance especially under drought stress. We investigated a series of indices of plant water balance under two water conditions to identify the mechanisms underlying this process in seedlings of four wheat cultivars released in Shaanxi Province, China, from the 1960s to the present decade. The newer cultivars maintained good water status under well-watered conditions by a high uptake of water by roots. The various cultivars released at different times, however, maintained whole-plant water balance differently under osmotic stress. The newer cultivars decreased water loss by decreasing foliar stomatal conductance and severely down-regulating TaPIP1-2, a gene encoding an aquaporin. The expression of root aquaporin genes was higher in the older cultivars than in the newer cultivars. Root hydraulic conductance was significantly and positively correlated with the relative expression of another aquaporin homologue, TaPIP2-1. The older cultivars maintained high levels of transpiration by a relatively high root hydraulic conductance or a large root surface area. The newer cultivars, with lower root hydraulic conductance, maintained water balance by synchronously decreasing foliar water loss. Wheat breeders should seek more effective solutions for improving the capacity of roots to take up water and for reducing foliar water loss to be able to cope with the expected lower availability of water resources for agriculture in the future.

Key words: Wheat; Plasma intrinsic proteins; Hydraulic conductance; Transpiration.
 

¹State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling 712100, China

²State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling 712100, China

³University of Chinese Academy of Sciences, Beijing 100049, China

^*Corresponding author’s email: sqzhang@ms.iswc.ac.cn; Tel.: +86 29 87010897; fax: +86 29 87012210