Along with typical plants, modified shoots often develop, which is associated with the performance of other functions by them.
Shoot modifications are modifications of parts of the stem – adaptations that help plants survive and adapt to adverse circumstances. Some perennial herbaceous plants have a peculiar underground storeroom. The aerial parts of these plants die off annually by autumn. Roots and modified underground shoots – rhizomes, tubers and bulbs – remain in the soil. It is in them that the reserves of organic matter are deposited for the winter.
1. Rhizome is a perennial underground shoot that gives new shoots after wintering. The rhizome is of great importance for vegetative propagation, since it has buds from which a new plant can grow.
Example: many plants have rhizomes, including nettle, wheatgrass, iris, lily of the valley.
The lily of the valley has a rhizome. All parts of the plant are poisonous.
Common liverwort, can bloom in early spring, as it uses the nutrients accumulated in the rhizome.
Irises are widespread ornamental plants that reproduce using rhizomes.
2. A tuber is a thickened part of the stem in which nutrients accumulate.
Example: tubers are found, for example, in potatoes, corydalis, Jerusalem artichoke (ground pear) fodder plant.
Underground shoots, on which potato tubers develop, grow from the bases of aboveground stems; these shoots are called stolons.
Tubers are apical thickening of stolons. The tubers have buds, which are called “eyes”. There are more eyes on the side of the tuber, which is called the tip. On the opposite side – the base – the tuber is connected to the stolon. Organic matter constantly flows from the leaves of the potato through the stems into the stolons and is deposited in the tops in the form of starch. The tops of the stolons grow, thicken, and by autumn they turn into large tubers.
3. A bulb consists of a bulb base and many closely spaced leaves and adventitious roots.
In the lower part of the onion bulb there is an almost flat stem – the bottom (if the bulb is planted in the ground, a fibrous root system forms on the bottom side of the bottom). On the bottom there are modified leaves – scales. The outer scales are dry and leathery, while the inner ones are fleshy and juicy. They contain reserves of water with sugar and other substances dissolved in it. The presence on the bottom of the buds located in the axils of the scales confirms that the bulb is a modified shoot.
Example: bulbs form perennial plants – onions, lilies, tulips, daffodils, wild goose onions.
From the apical bud of the bulb, an aerial shoot develops, for example, the stem, leaves and flower of a tulip. Sometimes young bulbs, called babies, develop from the buds. Each baby bulb can grow an independent plant.
Aboveground modifications of the shoot are thorns of wild apple, pear, hawthorn, which protect plants from being eaten by animals.
Kohlrabi has a modified aerial shoot, which is a thickening of the internodes of the stem.
Antennae are formed from various terrestrial parts of the plant.
Example: tendrils of grapes, cucumbers, pumpkins, melons – modified shoots. In peas and peas, some leaves of compound leaves are modified into antennae (their antennae are modified leaves). With the help of antennae, peas are attached to the support and “climb” up.