Question

Реферат 2класс тема стебель

Answer 1

Внешнее строение стебля. Стебель — это осевая часть побега, состоящая из узлов и междоузлий. В зависимости от степени вытянутости междоузлий стебель может быть удлиненным или укороченным. Так, у подсолнечника, кукурузы, астр, гладиолуса стебель удлиненный. А у подорожника, одуванчика, маргаритки, примулы, сенполии стебель укороченный.

Answer 2

The Stem: An Overview

The stem is an important part of a plant's anatomy. It serves as the main structural support for the plant and plays a crucial role in transporting water, nutrients, and sugars between the roots and leaves. In addition, the stem also provides a platform for the attachment of leaves, flowers, and fruits.

Structure of a Stem

The stem is composed of several layers and tissues that work together to perform various functions. The outermost layer of the stem is called the epidermis, which acts as a protective barrier against water loss and pathogens. Just beneath the epidermis is the cortex, which stores food reserves and provides mechanical support.

The vascular tissue, consisting of xylem and phloem, is located in the center of the stem. Xylem transports water and minerals from the roots to the leaves, while phloem carries sugars produced during photosynthesis from the leaves to other parts of the plant. The arrangement of xylem and phloem varies depending on the type of plant.

Types of Stems

Stems can be classified into different types based on their structure and function. Here are a few examples:

1. Herbaceous Stems: These stems are soft, green, and flexible. They are typically found in non-woody plants, such as grasses and annual flowers.

2. Woody Stems: Woody stems are hard and rigid, providing strong support to the plant. They are found in trees and shrubs and are composed of secondary growth, which increases the stem's girth over time.

3. Rhizomes: Rhizomes are horizontal underground stems that grow horizontally and produce new shoots and roots. Examples include ginger and iris plants.

4. Stolons: Stolons, also known as runners, are horizontal stems that grow above the ground. They produce new plants at nodes along their length. Strawberries are an example of plants that spread through stolons.

5. Tubers: Tubers are swollen underground stems that store food reserves. Potatoes are a well-known example of tubers.

Functions of the Stem

The stem performs several important functions in a plant's life cycle. Here are some key functions:

1. Support: The stem provides structural support to the plant, keeping it upright and allowing it to reach towards the sunlight.

2. Transport: The stem contains vascular tissues, such as xylem and phloem, which transport water, nutrients, and sugars throughout the plant.

3. Storage: Some stems, like rhizomes and tubers, store food reserves that can be used during periods of dormancy or for new growth.

4. Vegetative Propagation: Certain stems, such as stolons and rhizomes, can produce new plants through vegetative propagation, allowing the plant to spread and reproduce.

Conclusion

In conclusion, the stem is a vital part of a plant's anatomy, providing support, transportation, and storage functions. It comes in various forms, such as herbaceous and woody stems, rhizomes, stolons, and tubers. Understanding the structure and functions of the stem helps us appreciate the complexity and adaptability of plants.