November 28, 2021
Leaves generally refer to the organs of plants that perform photosynthesis and respiration. It is flat, with veins of leaves, and it extends to every corner of the leaves.
In botany, it refers to the lateral organs formed at the stem apex (tip of the stem), so in addition to the above, calyx, petals, ovary, carpel (the source of the pistil), bracts. , Including bracts, etc. Some of these are explained in "Special Structures".
Here, the leaves of broad-leaved trees such as cherry blossoms and camphor trees will be described by regarding broad-leaved trees (dicotyledonous plants) as typical. In addition, moss also has a leaf-like structure.
Structure and features
The leaves are organs for photosynthesis. The thin and wide structure seems to be an adaptation for efficiently absorbing the sunlight and exchanging gas.
The leaves are the parts that emerge from the stem and spread flat, where they usually do not sprout. It has a certain lifespan, and when the time comes, it is cut off from the root and abandoned. That is, it withers and leaves fall.
There are various shapes depending on the species and function. It is often flat and spreads horizontally to make it more susceptible to light. The part that connects to the branch is slightly thicker to support the entire leaf, and when it can be distinguished from the leaf body and the branch, it is called a petiole. The body of the leaf is called the leaf blade. Leaf blades come in a variety of shapes, but the most common are oval or similar. There are various shapes and characteristics, and it is a characteristic of each species.
The appendage at the base of the leaf is called the leaf. It is often like a small leaf, but it can be exceptionally large or turned into a spine or tendril. In many cases, the leaves do not exist, or even if they do exist, they fall off immediately.
Many monocotyledonous plants are in the form of elongated leaves. In particular, many gramineous plants are rather hard and have elongated leaves that stand up, and are said to be suitable for life in grasslands. It is a form in which light can easily enter to the root and photosynthesis can occur throughout the plant.
Many gymnosperms such as pine have thin leaves like needles, and are collectively called coniferous trees. On the other hand, many angiosperms have wide leaves, and such trees are called broad-leaved trees.
It can be seen in many cases that plants deform their leaves to accommodate a variety of uses. In particular, what is common to almost all plants is the response to reproduction. In the lineage to which the seed plant belongs, spores occur on the leaves, and various leaf deformations associated with them are observed. The flowers and their elements, petals, stamens and pistils, are also leaf variants, and therefore the fruits are also considered to be derived from the leaves.
For plants, leaves are an important point of contact with the environment and also the weakest part. Therefore, depending on the growing environment, there are leaves of various shapes, and at first glance they may not look like leaves.
The leaves are also vulnerable to dryness and show various adaptations. Usually, many of them are thick and small, or develop a mechanism for storing water in the leaves. In particular, plants that grow in drylands and store water in such leaves and stems are called succulents. In particular, the special adaptation of leaves is that, as seen in cacti, leaves are no longer used as anabolic organs and have become spines.
In carnivorous plants, the leaves are deformed into various shapes to develop a mechanism for catching, digesting and absorbing insects. �