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Effects of water deficit on gas-exchange parameters and ribulose 1,5-bisphosphate carboxylase activation in wheat

1992; Elsevier BV; Volume: 32; Issue: 4 Linguagem: Inglês

10.1016/0098-8472(92)90053-5

1873-7307

A. Scott Holaday, Steven W. Ritchie, Henry T. Nguyen,

Plant Stress Responses and Tolerance

Two spring wheat (Triticum aestivum L.) genotypes, Anza, drought resistant, and Chenab 70, drought susceptible, were used to study the effects of a slowly developing water stress on gas-exchange parameters and ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBPCase; EC 4.1.1.39) activities. By day 7 of the experiment, the two genotypes exhibited similar declines in stomatal conductance (g) (by 77%) and photosynthetic CO2 assimilation rate (A) (by 33%). However, their leaf relative water content (RWC) was still 90% and total (CO2/Mg2+ activated) RuBPCase activities had declined only by 12%. By day 12, RWC decreased to 67% for Chenab 70 and 58% for Anza plants, while g was reduced by more than 95%, and A was reduced by 71% for both genotypes. Thus, Anza plants maintained the same A as Chenab 70 plants even though their RWC was less. Total soluble protein decreased by 30% for Chenab 70 and 43% for Anza plants, while a 12% average reduction in chlorophyll occurred. Over the 12-day experiment, an average 31% reduction in RuBPCase activity occurred for both genotypes. However, the proportion of RuBPCase in the activated state did not change (for Anza) or declined by only 9% (for Chenab 70) over the course of the experiment. These data suggest that changes in in vivo RuBPCase activities are not a major consequence of moderate to severe water deficits in spring wheat.