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Nonuniform stomatal closure in leaves of wheat and soybean

Meng Qingwei, Zou Qi, Xu Changcheng, Zhao Shijie

Shandong Agricultural University. Taian 271018, Shandong

Abstract

The occurrence of “patchy”pattern of CO_(2) uptake across the surface of leaves was examined in wheat and soybean under field conditions by ~(14)CO_(2) autoradiography. Well-watered leaves had uniform distribution of photosynthesis. Plant water deficits causing a leaf water potential depression to -1.75 MPa in wheat and -1.32 MPa in soybean resulted in nonuniform CO_(2) assimilation patterns. The leaf water potential at which nonuniform stomatal closure occurred in soybean was not as low as that in wheat. Nonuniform stomatal closure occurred when a leaf was subjected to a rapid dehydration in air for a few minutes.An increase in the calculated value of intercellular CO_(2) concentration was often observed.The increase probably resulted from an erroneous calculation due to “patchy” stomatal closure,but might also be caused by an enhanced photorespiration or respiration rates.When the photosynthetic rate of wheat flag leaves showed midday depression under field conditions on clear days,nonuniform stomatal closure was not observed.Soybean leaves,on the other hand,sometimes showed nonuniform stomatal closure when midday depression occurred with an increase of Ci. Higher VPD during midday period was probably the main factor causing nonuniform stomatal closure of soybean leaves. It is not certain whether the observed increase of intercellular CO_(2) concentration in soybean leaves was due to nonstomatal limitalion or an overestimation due to “patchy” stomatal closure, or both. It is suggested that,whenever nonuniform stomatal closure takes place,one should not infer the occurrence of nonstomatal limitation of photosynthesis from an increase of Ci.

Key words: ~(14)CO_(2) autoradiograph;Nonuniform atomatal closure;Midday depression of photosynthesis;Wheat;Soybean

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Citing This Article：

Meng Qingwei, Zou Qi, Xu Changcheng, Zhao Shijie. Nonuniform stomatal closure in leaves of wheat and soybean. Acta Physiol Sin 1997; 49 (1): (in Chinese with English abstract).