Author: Shu-Hsien Lee
J Integr Plant Biol 1952, 1 (1): -.
Five species of the bulb crops simultaneously grown in China were used in this study. Namely garlic, Allium sativum L. onion, A. cepa L.; Welsh onion, A. fistulosum L.; scallion, A. Backeri Ragel; and Chives (Kiu-tsai,) A. tuberosum Rottler ex Sprengel. They may be distinguished by the following key based on the structure of the leaves.
A. Mature leaf hollow, with a large central lacuna.
B. Mature leaf triangular in transverse section……………A Backeri
BB. Mature leaf fistular and terete in transverse section.
C. Leaf larger and stronger, palisade tissues usually glayered, with a large bulb ….A. cepa.
CC. Leaf smaller and weaker, palisade tissues usually 2-layered, with a smaller bulb. ……..A. fistulosum.
AA Mature leaf, flat and solid or nearly so, with more stomata and smaller vascular bundles on the ventral side than on the dorsal side of the leaf.
B. Leaf broader, up to 2 cm. wide, somewhat conduplicate in cross section, acute at apex…… A sativum
BB. Leaf linear and narrower, few exceeding 1 cm. in width, obtuse at apex….. A. tuberosum.
Like other monocotyledons, of which the leaves are usually borne vertically or nearly so, there was only a slight difference in the number of stomata per unit area between the dorsal (abaxial) and ventral (adaxial) sides of the leaves in all the five species of Allium herein studied. As a rule, there are about 100 stomata per square centimeter on the ventral epidermis more than those on the dorsal epidermis. These differences were found to be greater in the species with solid and flat leaves than those with fistular or terete leaves. There is no appreciable difference in the number of stomata per unit area between the leaves under soil blanching and those under ordinary culture. The practice of blanching, no matter what method is used, may reduce the chlorophyll content in the mesophyll, and the lignification of the cell wails, but do not affect the development and number of the stomata. The number of stomata per unit area varies not only from species to species, but also from leaf to leaf of the same plant, and even from different portions of a single leaf. In the case of blanched chives (Kiu-tsai), there are no stomata on the ventral side and only a few hundred stomata per square centimeter on the dorsal side of the leaf sheath. The number of stomata in the leaf blade is greatly increased from outer (older) to inner (younger) leaves of a single plant, and that on the ventral side is generally greater than that on the dorsal side. The scale-like membrane which is equivalent to the sheath of a normal leaf, consists only one stoma per square centi meter in average.