What Plants Need Surviving as stationary organisms on land is a difficult task that most plants face. Plants have developed a number of adaptations that enable them to succeed. The lives of plants center on the need for sunlight, gas exchange, water, and minerals. These basic needs are illustrated in Figure 22–2.

▸ Sunlight Plants use the energy from sunlight to carry out photosynthesis. As a result, every plant displays adaptations shaped by the need to gather sunlight. Photosynthetic organs such as leaves are typically broad and flat and are arranged on the stem so as to maximize light absorption.

▸ Gas Exchange Plants require oxygen to support cellular respiration as well as carbon dioxide to carry out photosynthesis. They also need to release excess oxygen made during photosynthesis. Plants must exchange these gases with the atmosphere and the soil without losing excessive amounts of water through evaporation.

▸ Water and Minerals On a hot sunny day, plants can lose a great deal of water to the air, just as we sweat when we are hot. Also, water is one of the raw materials of photosynthesis, so it is consumed when the sun is shining. Thus, land plants have evolved structures that limit water loss and speed the uptake of water from the ground.

As they absorb water, plants also absorb minerals. Minerals are nutrients in the soil needed for plant growth. Many plants have specialized tissues that carry water and nutrients upward from the soil and distribute the products of photosynthesis throughout the plant body. Simpler types of plants carry out these functions by diffusion.

In Your Notebook Outline the basic needs of plants. Under each head, add supporting details.

FIGURE 22–2 Basic Needs of a Plant All plants have the same basic needs: sunlight, a way to exchange gases with the surrounding air, water, and minerals. Observe Where do water and minerals enter the plant?

Table of Contents