The leaf shape of ginkgo is also affected by the angle of the fork on both sides of the leaf base. A close look at the leaves of a group of live trees reveals a wide variation in the shape of the ginkgo leaf primordium, from curved, to triangular, to arrow-shaped. This is related to the degree of development of the leaf primordium and differs markedly from species to species. Generally long son type, Buddha's hand type varieties, leaf base tends to be close to the triangle; and plum nuclear type, longan type varieties, leaf base two sides of the angle is often greater than 180 degrees, curved, the whole leaf looks from the side, like a waist.
Ginkgo biloba, roughly do not distinguish between positive and negative, in fact, the positive and negative side of the ginkgo biloba also have obvious differences. Ginkgo biloba front, dark green in color, glossy, generally hairless, while its back, light green, with a large number of downy hairs or cilia, only a few hairless. When hairy, the color tends to be silvery white.
Ginkgo biloba generally has a deeper cleft in the center that divides the leaf into two roughly equal halves. For each half, there are generally 2-4 other shallow cracks. The depth and number of ginkgo biloba fissures are related to the seed source, species, sex, age and growth conditions, management measures. General male tree leaf fissures deeper, female tree leaf fissures shallower; young tree leaf fissures deeper, adult tree leaf fissures shallower; small-grain varieties of leaf fissures deeper, large-grain varieties of leaf fissures shallower; growth of trees and parts of the tree leaf fissures deeper, growth of median trees and parts of the tree leaf fissures shallower. Some people had the depth of the middle crack as the basis for judging the male and female sex of ginkgo. This method is not reliable. Because, from the base of the female tree sprouted branches, growth is particularly vigorous, the leaves also have the depth of the lack of carving, cracks are also very deep.
Ginkgo leaves, generally 5.0-5.3 centimeters long, up to 8 centimeters long; generally 7.0-8.5 centimeters wide, up to 11.5 centimeters wide. The area of each leaf blade is 4.0-32.0 square centimeters. The size of the leaf area is related to the strength of the tree. When the tree is overfruitful and weakened for various reasons, the area of a single leaf will be drastically reduced, and the number of leaves on each bell branch, too, will be reduced, and the leaves may even fall off early. Therefore, the number of leaves on each bell branch, the average value of leaf area per leaf, as well as the early and late leaf shedding of the fruiting plant can be used to determine whether the plant can be normal flowering and fruiting in the second year. Taking the Taixing Buddha finger as an example, if there are more than six leaves on the bell branch, the leaf area is normal, the leaves can be preserved until early November, generally the second year can still be productive.
The leaf veins of ginkgo biloba, in a dichotomous branching way outward. The number of branches, usually 3-4. Arnott H.J. (1959) carefully examined thousands of ginkgo biloba leaves and found that linkage of the leaf veins could be seen in about 10% of the leaves. He also classified the leaves into four types, depending on the number of dichotomous branches included and the presence or absence of dichotomous branches at the fusion of the leaf veins. This phenomenon of few unions on the leaf veins is considered to be a regressive phenomenon, as this configuration is similar to that of the leaflets of certain true ferns and sauropods.
The petiole of a ginkgo biloba is, in fact, a cluster of vascular bundles made up of a collection of many leaf veins. It is generally 5.5-7.0 centimeters long, with a maximum length of 12.1 centimeters and a minimum length of only 2.0 centimeters. Leaf blades borne on the same bell branch not only differ in blade shape and leaf area, but also in petiole length. Here, in addition to the influence of growth conditions, but also related to the variety.
The upper epidermis of the ginkgo biloba, has a distinct cuticle. The cuticle consists of two types of elongated cells. On top of the leaf blade, there are many dark-colored linear secretory grooves distributed. The epidermal cells that are in the parallel course of the leaf veins and the leaf veins are small, narrow and tightly arranged. The cells in between the two veins are long and wide, closely set and neatly arranged. The upper epidermis of the leaf has no stomatal apparatus, or only a few incompletely developed stomatal apparatus. The lower epidermis has more stomatal apparatus, and the guard cells are concave, often ovate or fusiform. The secondary guard cells are 5-7 in number, enclosing a ring with a smooth or hairy surface. The lower epidermis of the leaf consists of many irregular wave-shaped flat cells. The epidermal cells are densely toothed at their contacts and are embedded in each other. Below the upper epidermis is the fenestrated tissue, consisting of tightly arranged fenestrated tissue cells in long strips. The cells contain more chloroplasts. Spongy tissue consists of irregular round cells, also containing more chloroplasts.
Ginkgo biloba against a variety of pathogenic bacteria attack ability is stronger. This is also the ginkgo can continue to exist for 200-300 million years without extinction of the important reason. Some germ spores moisturizing inoculation to the ginkgo biloba, although they can sprout and form mycelial network, but it is difficult to penetrate the cuticle of the ginkgo leaf surface and infringement of its organization. On the contrary, this time the cell wall of ginkgo biloba leaves will be thickened accordingly. This thickening phenomenon also occurs when the leaf veins are mechanically damaged. This effectively prevents the attack of pathogenic bacteria. In addition to the anti-disease mechanism of the foliar structure, the polyvinylaldehyde and a variety of organic acids contained in the leaf blade also have obvious bacteriostatic and insecticidal effects.