Give a short overview of transportation of substances in plants

Answer 1

Transportation of substances in plants is a vital process that allows them to transport water, nutrients, and various substances throughout their different parts. There are two main types of transportation in plants: transport of water and minerals through the xylem, and transport of sugars and other organic molecules through the phloem.

Xylem is responsible for the upward transport of water and minerals from the roots to the leaves and other aerial parts of the plant. This transport is driven by a combination of transpiration (evaporation of water from the leaves) and cohesion-tension mechanism. Water is absorbed from the soil through the roots and moves up through the xylem vessels, forming a continuous column due to cohesive forces. Small pores called stomata on the leaf surface allow water to evaporate, creating a pull that helps in drawing more water from the roots.

Meanwhile, the phloem transports sugars, amino acids, hormones, and other organic molecules produced in the leaves or storage tissues to the rest of the plant. This transport occurs in both upward (source to sink) and downward (sink to source) directions. The movement of substances in the phloem is mainly driven by pressure flow mechanism. Sugars are actively loaded into the phloem cells of a source (e.g., leaves) and this creates a high concentration gradient. As a result, water moves into the phloem by osmosis, increasing the pressure inside. This pressure gradient allows the phloem sap to flow from the source to the sink, where the stored sugars and other substances are utilized or stored.

Overall, the transportation of substances in plants is a complex and coordinated process, involving specialized tissues (xylem and phloem) and various mechanisms such as transpiration, cohesion-tension, and pressure flow. This efficient transport system ensures the distribution of water, nutrients, and organic molecules throughout the plant, supporting its growth, metabolism, and overall functioning.