Question

The manufactured food in a green plant moves leaves to other parts through (a) xylem (b) phloem (c) cortex (d) pith.

Short answer

The manufactured food in a green plant moves from leaves to other parts through (b) phloem.

Step-by-step solution

Understanding the function of plant tissues

In plants, different tissues have different functions. The xylem primarily transports water and minerals from the roots to the leaves, while the phloem is responsible for distributing the sugars and nutrients produced during photosynthesis, from the leaves to other parts of the plant.

Identifying the correct tissue for transportation of food

Knowing the functions, you can determine that the phloem is the tissue through which manufactured food (sugars and organic substances) moves from the leaves to the rest of the plant.

Key concepts

Phloem Transportation

When we think about how plants distribute the sugars they create, we are referring to the role of the phloem. The phloem is a complex tissue system in vascular plants, primarily responsible for the translocation of organic nutrients, particularly the sugar sucrose, from the photosynthesizing leaves to various parts of the plant.

This process is critical for the growth and development of a plant. Imagine the phloem as an elaborate highway system, with on-ramps and off-ramps, through which these essential nutrients travel to reach their destinations. This includes growing tissues like the stems and roots, as well as storage organs like tubers and bulbs.

The movement within the phloem is driven by a process known as translocation, which operates on the principle of pressure flow. Essentially, sugar is loaded into the phloem tissue, which increases the pressure, causing the contents to flow towards areas of lower pressure where the sugar is needed or will be stored. This unique transportation system ensures that energy produced in the leaves can sustain the entire plant.

Xylem Water Transport

The xylem, on the other hand, functions much like the plumbing system of a plant, conducting water and dissolved minerals from the roots up to the leaves. As you may recall from the exercise, xylem does not play a role in transporting the food produced by photosynthesis.

Water uptake is a result of the combination of two forces: transpiration and root pressure. Transpiration is the process of water evaporation from the plant’s surface, primarily through the leaves, creating a negative pressure that helps to draw water upwards. This acts somewhat like a straw, utilizing cohesion and adhesion properties of water molecules to maintain a continuous water column from the roots to the leaves.

Root pressure, although less significant than transpiration, contributes too, especially during periods of high soil moisture and low transpiration. Together, these processes enable the xylem vessels to transport water against gravity, irrigating even the highest leaves with life-sustaining moisture.

Photosynthesis Byproducts Distribution

Photosynthesis is the process by which plants use sunlight to produce glucose and oxygen from carbon dioxide and water. But what happens to these products once they are made? Oxygen, as a byproduct of photosynthesis, is largely released into the atmosphere through stomata — tiny openings on the leaves.

The glucose, however, is not just food for the plant; it's also a building block for more complex sugars and starches that the plant uses for structure and storage. This is where the photosynthesis byproducts distribution comes into play.

Glucose and other nutrients are converted into a form that can be transported by the phloem to other parts of the plant where they are either used immediately for energy, used to build cell walls (in the form of cellulose), or stored for future use. This system ensures a consistent distribution of food and nutrients, which is vital not only for the plant’s growth and repair but also for its ability to reproduce and create new seeds.