30 Transport Systems in Plants-Mid

Transport Systems in Plants FOCUS Question How do plant cells work together to move nutrients?

From Tiny to Tall Imagine Earth without bushes or trees. Millions of years ago, the only plants were tiny and low to the ground, like the mosses of today. These were nonvascular plants plants— with no special system of tubes and tissues to move water and nutrients. A plant won't grow taller if the upper part of the plant can't get what it needs to survive. Today, a vast variety of plants cover Earth! Vascular plants have tubes in their roots, stems, and leaves to move nutrients, food, and water. With this transport system, vascular plants, like giant redwood trees, can grow taller than 90 meters (300 ft.) That's a long way to move water, food, and nutrients. Wowser! The world's tallest tree is Hyperion, a tree in Redwood National Park in California. It's approximately 116 meters (381 ft.) tall.

Flow Through Plant Parts You probably know the main parts. of a plant But do you know how they each move water, food, and nutrients throughout the plant? Roots Roots not only anchor a plant in the ground; they pull water and nutrients from the soil. There are many tiny hairs on the roots, called root hairs, which help absorb water. One hair can't absorb a lot, but think how much water thousands of hairs can absorb. Roots also provide storage for the plant. Food is made in the leaves and flows down toward the roots. Plants use food to grow and maintain their tissues. They store extra food in their roots in the form of starch for times when they aren't able to make new food.

Leaves Leaves differ greatly in size and shape They can be single, simple leaves or clusters of small leaflets called compound leaves. Even the needles on a pine tree and the spines on a cactus are leaves. Leaves gather sunlight and carbon dioxide from the air. They combine it with water to make sugars, the food for the plant. This process is called photosynthesis. Veins in a leaf bring in water and minerals. The veins also send food from the leaf to other parts of the plant. Tiny holes in the leaf let gases flow, letting carbon dioxide in and oxygen out. These holes are called stomata. Water exits stomata through the process of evaporation. This special kind of evaporation used by plants is called transpiration.

Stems The stem holds the plant upright and connects the roots to branches and leaves. Within the stem of vascular plants are special tissues that transport substances throughout the plant. The xylem (ZY-lum) moves water and minerals from the roots to the leaves. Xylem cells are long and thin. They die soon after they form, but their hard structure remains. Xylem cells form a pipeline from the roots to the stem or trunk. The pipeline splits off into branches and moves into every leaf. Do You Know? When you observe tree rings, you are looking at the remains of old xylem tissue.

The phloem (FLOW-um) carries food from the leaves to other parts of the plant. Phloem cells are long and connected to one another throughout the entire plant. Unlike xylem cells, phloem cells remain alive for the life of the plant. In trees, the phloem is the innermost part of the bark. It must not be damaged or the tree might die. In some plants, the xylem and phloem are scattered throughout the plant in no particular order. In others, xylem and phloem are arranged in a ring around the edge.