Studies on the variability of stomatal density in soybean cultivars. I. Influence of leaf sides and leaf positions on the differences among cultivars.

Abstract

This study was planned to know how the leaf sides and leaf positions influence on the differences among cultivars in soybean. Experiment A : Differences among cultivars in stomatal density and its two components. Five and twelve cultivars were used as materials in 1979 and 1980, respectivery. Each plant was grown in a pot, in a natural-light phytotron with a temperature of 30°C during the day (06.00-18.00) and 25°C during the night. Only central leaflets in the component leaves of main stem were observed. The copies of epidermis were taken with manicure liquid from the central position between mid rib and leaf margin, in a fully expanded leaflet. Stomatal density (number of stomata per unit of surface area of epidermis, SD) is devided into two components, (1) the power of stomatal differentiation (ratio of stomatal number to epidermal cell number, PS), and (2) the epidermal cell size (surface area of an epidermal cell, EC). The relationship among SD, PS and EC is shown in the equation (1), on condition that the guard cell has very small surface area compared to the epidermal cell. Both in SD and PS, the values were a half smaller in adaxial side than in abaxial side at every leaf positsons (Table 2). Contrary to this, the values in EC did not differ so much with leaf sides (Table 2, Table 5). F values with leaf positions showed significant levels in SD, PS and EC (Table 4). But, the variabilities of SD among laef positions were smaller than those among leaf sides (Table 2). Differences among the cultivars in SD, PS and EC were also significant statistically (Table 3, Table 4). In adaxial leaf side, SD showed high positive correlation with PS, but did'nt show significant correlation with EC (Table 6). Contrary to this, SD in abaxial leaf side showed relatively high negative correlation with EC, and moreover showed lower positive correlation with PS compared to the case of adaxial side (Table 6). Experiment B : Observation on differentiation of stomata with the course of leaflet growth. Staining surface method (Table 1) was adopted for the observation, using the central leaflet of third leaf position in main stem of two cultivars as materials. It was found from the observations that the stomata began to differentiate after the epidermal cells had already differentiated moderately, and that the stomata began to differentiate somewhat earlier in abaxial leaf side than in adaxial leaf side (Fig. 1, Fig. 3). The patterns of change in EC and PS during leaflet growth were wholly differed each other (Fig. 2, Fig. 3). Between the two cultivars, the differentiation of stomata was earlier in Tokachi Hadaka than in Akiyoshi (Fig. 3). From the above results, the relation was shown that the process patterns of SD with the course of leaflet growth were differed between the two cultivars, especially in adaxial leaf side (Fig. 4).