Each of us noticed that the leaves on plants are arranged in a certain way. Biologists call this phenomenon phyllotaxis. From our article you will learn what a whorled leaf arrangement is and in which plants it occurs in nature.
Types of phyllotaxis
At an apple tree and a wild rose, only one leaf departs from the node. The rest are arranged in a spiral relative to each other. This type of phyllotaxis is found in plants of the family Umbelliferae, Cereals, Birch and Bukotsvetnye. It is called regular or spiral.
With opposite phyllotaxis, there are two leaves in the node, which are located opposite each other. Examples of such plants are sage, mint, motherwort, rosemary, basil, lemon balm.
Whorled leaf arrangement: plant examples and features
But plants with whorled phyllotaxis are not so common in nature. In such species, several leaves develop at once on one node.
Annular leaf arrangement (as the whorl is also called) is considered the most profitableto effectively absorb sunlight. In this case, the leaves practically do not obscure each other. Moreover, their total area is much larger than that of the plant itself. As examples of plants with annular leaf arrangement, one can cite representatives of the families Melantievye, Kutrovye, as well as the genus Vodokrasovye.
Tiered categories
Leaves located on different parts of the shoot are morphologically and functionally different from each other. According to these features, they can be grouped into three groups:
- Grassroots perform the function of protection and supply of nutrients. Develop at the bottom of the leaf. At first they are white, but over time the shade changes to brown or black.
- Medium - photosynthetic green leaves with large plates. Develop in the middle part of the shoot.
- Horse - leaves located in the area of inflorescences. They are underdeveloped, poorly dissected. Their green color is not for photosynthesis, but to attract insects.
The whorled leaf arrangement allows each plate to make the most of the light. If the leaves grow in a horizontal or vertical plane on petioles of unequal height, a so-called mosaic is formed. It can be observed in plants with different phyllotaxis, including whorled.
Which plants have a whorl?
Several leaves in one node often develop in conifers. This isjuniper, spruce, pine, cypress. Their leaves are needle-shaped and are called needles. This structure prevents excessive loss of moisture in the cold season. But for the implementation of photosynthesis, the needles must be arranged in "bundles".
Whorled leaf arrangement is also characteristic of many ornamental plants. It can be found in lilies and oleander. Their leaves have a rich green color and a waxy coating, which makes these plants visually more attractive.
Horsetail is also an example of species with a whorled leaf arrangement. It belongs to the group of higher spore plants. Moreover, only the summer shoot performs the function of photosynthesis, in the rosettes of which thin wedge-shaped leaves develop.
Elodea is a typical example of an aquatic plant with whorled phyllotaxis. Each node of the shoot develops three leaves with a rounded oblong plate. They are transparent, bright green in color, located on long shoots. This structure makes Elodea a real decoration of aquariums and ponds.
So, the annular or whorled leaf arrangement, examples of which we examined in the article, is characterized by the presence of several plates in one node. In this case, they do not shade each other, contributing to the efficient flow of the photosynthesis process.
