Transport in plants (xylem and phloem) — KCSE Biology

In plants, the transport of water and food is vital for their survival. Xylem and phloem are the two main tissues involved in this process.

1. Water Transport (Xylem):

   • Water is absorbed by the roots from the soil.
   • It moves upwards through the xylem vessels via capillarity and transpiration pull.
   • Transpiration is the evaporation of water from leaves, creating a negative pressure that pulls water up.

2. Food Transport (Phloem):

   • Photosynthesis occurs in leaves, producing glucose.
   • The glucose is then converted to sucrose and transported through phloem.
   • This process is driven by pressure flow, where sucrose concentration creates a pressure gradient, moving sap from source (leaves) to sink (roots and fruits).

Understanding these mechanisms is essential as they ensure that plants receive the necessary nutrients and water for growth and development.

In plants, transport occurs mainly through two types of vascular tissues: xylem and phloem.

• Xylem is responsible for the transport of water and minerals from the roots to the leaves. It consists of hollow tubes made of dead cells, which allows for efficient upward movement of water through capillary action and transpiration pull.
• Phloem, on the other hand, transports organic nutrients, particularly sugars produced during photosynthesis, from the leaves to other parts of the plant. It is composed of living cells that facilitate the flow of nutrients through active transport and diffusion.

Both xylem and phloem play crucial roles in maintaining plant health and growth by ensuring that essential substances are delivered where needed.

In summary, xylem transports water and minerals, while phloem distributes nutrients throughout the plant.