Plant Structures

Plants have a vascular system, similar to the circulatory system in animals, for the transportation of substances over larger distances.
The vascular system in plants consists of xylem and phloem tissues.
Xylem tissue is responsible for the transport of water and minerals from the roots to the stem and leaves. The transport in xylem is unidirectional, i.e., from roots to other parts.
The mechanism of water transport in xylem is based on transpiration - the process of water evaporation from tiny pores, known as stomata, on the surface of leaves. This creates a suction pressure known as transpiration pull which pulls water up through the xylem vessels.
Phloem tissue carries out the function of transporting food substances like glucose and other organic materials, synthesized during photosynthesis. This process is called translocation.
Transportation in phloem occurs in both directions, i.e., from leaves (source of food production) to roots and other parts of the plant (sites of storage).
Translocation mechanism involves active transport - the sap (with high concentration of organic substances) is loaded into the phloem vessels which lowers the water potential within these vessels causing water to move in from surrounding tissues.
Roots play a key role in absorption of water and nutrients from the soil. This is facilitated by root hairs which increase the surface area for absorption.
Plants have a specialised tissue at their tips, the apical meristem, which allows for growth in length, while lateral meristems allow for growth in diameter.
Leaves, with their broad and flat nature, help in efficient light absorption for photosynthesis. Their stomata also facilitate gas exchange.
Special adaptation in plants for transportation includes the development of aerial roots in mangroves, for O2 intake in waterlogged soil conditions, and thorns in cacti to reduce water loss.
Plants constantly regulate water balance through the opening and closing of stomata. In dry conditions, plants can close stomata to prevent excessive water loss.