EFFECTS OF DROUGHT STRESS ON STOMATAL MORPHOGENESIS OF SOYBEAN VARIETIES

Stomatal frequency, dimension, size of aperture and pore area of six soybean varieties, including Dah liarn, Wakashima, Native 13, AGS 62, Sanluis and 66-F-4-2, under long-term drought stress were studied by microscopic method in order to study the responses of stomatal morphogenesis to drought stress. The results are summarized as follows. 1. Abaxial stomatal frequency of well-watered leaf was 280 and adaxial frequency was 102 per mm2. 2. Stomatal frequency increased 18% and stomatal dimension decreased 27% under severe drought stress. 3. Single stomatal aperture of well-watered adaxial epidermis was 2 approximately 3-mu-m2 greater than that of abaxial epidermis. But abaxial frequency was greater, so that pore area of abaxial epidermis was greater. 4. Whether drought stressed or not, both stomatal aperture and pore area of AGS 62 were the greatest among six varieties. Pore area of Native 13 was easily affected by drought stress. 5. Responses of stomatal morphogensis to drought stress differed with varieties. These responses could be used as indicators for selecting drought resistance.