Abstract
The number, size and morphology of vascular bundles were observed in transverse section at the base of leaf blades and at the center of leaf sheaths. The results were fundamentally the same in seven species of millets examined. The number and size of both large and small vascular bundles increased as the leaf position (shoot-unit) became higher (Fig. 2, 3). In the large vascular bundles, cross sectional area of phloem, cross sectional area of xylem and diameter of late metaxylem vessel were proportional to the size of the bundle (Table 1, 2, 3). But in the small vascular bundles, the cross sectional area of xylem was not in proportion to the size of the bundle, and smaller small vascular bundles had relatively smaller amount of xylem (Table 2). The total cross sectional area of phloem at the base of a leaf blade was larger than that at the center of leaf sheath. But the total cross sectional area of xylem in the leaf blade was smaller than that in the leaf sheath (Fig. 4). Large leaves had large total cross sectional areas of phloem and xylem, but the total cross sectional areas of phloem and xylem per unit leaf area were smaller than that of small leaves. The determining process and functional meaning of a quantitative relationship between the amount of conducting tissues and leaf were discussed.
