Each of us noticed that the leaves on the 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 in nature it occurs.
Types of phyllotaxis
In the apple tree and rose hips, only one leaf leaves the node. The rest, relative to each other, are arranged in a spiral. This type of phyllotaxis is found in plants of the Umbrella, Cereal, Birch and Buciferous family . It is called the next or spiral.
With opposite phyllotaxis, the node contains two sheets, 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 found in nature so often. In such species, several leaves develop on one node at once.
An annular leaf arrangement (also called a whorl) is considered the most beneficial for the effective absorption of 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. Representatives of the families Melantium, Kutrovy, and also the genus Vodokrasovye can be cited as examples of plants with a ringed leaf arrangement.
Tier categories
Leaves located on different parts of the shoot morphologically and functionally differ from each other. According to these signs, they can be combined into three groups:
- Grassroots perform the function of protecting and stocking up nutrients. Develop at the bottom of the sheet. At first they are white, but over time the hue changes to brown or black.
- Median - photosynthetic green leaves with large plates. Develop in the middle part of the shoot.
- Horse - leaves located in the field of inflorescences. They are underdeveloped, weakly dissected. Their green color serves not for photosynthesis, but for attracting insects.
The whorled leaf arrangement allows each plate to maximize the use of 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 various phyllotaxis, including whorled.
Which plants have a whorl?
Several leaves in one node often develop in conifers. This is juniper, spruce, pine, cypress. Their leaves are needle-shaped and are called needles. This structure prevents excessive moisture loss in the cold season. But for the implementation of photosynthesis, the needles need to be located "bunches".
A 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.
Field horsetail is also an example of a species with a whorled leaf arrangement. It belongs to the group of higher spore plants. Moreover, the function of photosynthesis is performed only by the summer shoot, in the outlets of which thin wedge-shaped leaves develop.
Elodea is a typical example of an aquatic plant with whorled phyllotaxis. In each shoot node, three leaves develop with a rounded oblong plate. They are transparent, bright green in color, located on long shoots. This structure makes Elodea a real decoration for aquariums and ponds.
So, the ringed or whorled leaf arrangement, the 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 obscure each other, contributing to the efficient course of the photosynthesis process.