Epidermal Tissue System of Soybean Leaf Blades

[摘要] Epidermal tissue system in terminal leaflet of the first trifoliate leaf of soybean plant (cv. Raiden) was observed by clearing method, SUMP method and paraffin method. Four types of cells, i.e. stomata (guard cells), ordinary epidermal cells, setaceous trichomes and clavate trichomes were recognized in the epidermis. There were many stomata on both adaxial and abaxial epidermis covering mesophyll tissue, but few on epidermis above vein in which bundle sheath extention (BSE) developed until epidermis (Fig. 1, 2). Stomatal density (number of stomata per unit leaf area) in abaxial surface was higher than that in adaxial surface (Fig. 9). In both surfaces it was highest at the middle part of the leaf blade near the midvein and low at the leaf top, base and margin (Fig. 9). Setaceous and clavate trichomes were present mainly on both adaxial and abaxial epidermis above veins around which BSE developed and touched with the epidermis, where the basal cells of these trichomes came in contact with the BSE (Fig. 2, 4, 6, 7). The number of both trichomes per unit midvein length in abaxial epidermis was approximately twice that in adaxial epidermis, and in both sides of midvein the number was largest at the middle position of it (Table 1). Many setaceous trichomes were present also at the leaf margin (Fig. 3, 5). When soybean plants were exposed to dark with saturated air humidity, many water drops were identified on both surfaces of leaf blades (Fig. 8) and the distribution of them coincided with that of clavate trichomes. These results suggested an excessive water of leaf be exuded out through the following pathway; xylem→bundle sheath→bundle sheath extention→clavate trichome, where the last trichome acts as a hydathode. It was also suggested that setaceous trichomes too may play a role in water physiology of young leaves.

[学科分类] 农业科学（综合）