Transportation In Plants: Overview, Process, Structure

Definition Of Transportation

Plant transport is the transportation of water, nutrients, and other essential chemicals in a plant. It ensures a plant's health. Transport requires growth, an aspect which further allows plants to perform photosynthesis and respiration.

Some of the major processes in plant transport involve the uptake of water and minerals by roots, the flow of these substances through the xylem, the distribution of sugars and other organic compounds through the phloem, and how stomata control transpiration in leaves by regulated opening. All these mechanisms are of importance to understanding perfecting plant care and increasing agriculture productivity.

Types Of Transport Systems In Plants

There are 2 kinds of transport systems in plants.

Vascular Tissues

Two kinds of vascular tissues are present in plants.

Xylem

• Comprises of tubular structure

• Includes tracheids, vessel elements, fibres, and parenchyma cells

Function

• Conducts water and dissolved minerals from roots to all parts of the plant

• Provides structural support

Types of Xylem Cells

• Tracheids: Long, thin cells with tapered ends; found in all vascular plants

• Vessel Elements: Shorter, wider cells with perforated end walls; primarily in angiosperms

Phloem

• Consists of living cells

• Comprises sieve tubes, companion cells, fibres, and parenchyma cells

Function

Conducts Organic nutrients, mainly sucrose, produced by photosynthesis from leaves to other parts of the plant

Types of Phloem Cells

• Sieve Tubes: The long tubes formed by sieve tube elements joined end-to-end; conduct nutrient transport

• Companion Cells: The cells which assist in conducting the process by providing pressure to the sieve tubes and giving them metabolic support

Means Of Transportation In Plants

There are three kinds of major transportation systems in plants.

Diffusion

It is said to be the flow of molecules from an area of high concentration to an area of low concentration.

Importance:

It plays a very significant or crucial role in the flow of gases, oxygen carbon-di-oxide and small solutes within the plant tissues.

Facilitated Diffusion

Movement of molecules across the cell membrane through some particular transport proteins.

Source-to-Sink Model

It quantifies nutrient flow from source to sink—for instance, roots, and fruits—where they are either utilized or stored.

Pressure Flow Hypothesis

This is used to explain the phloem sap flow due to the pressure difference between source and sink areas. This result follows because of the osmotic pressure and active transport mechanisms.

Active Transport

The process by which molecules move against their concentration gradient, thus prompting energy, which is typically derived from ATP.

Significance:

It primarily occurs during the absorption of indispensable minerals and nutrients from the soil, generically done to ensure there is ion balance within the plant cell.

Mechanisms Of Water Transport

The mechanisms of water transport are listed below-

Root Absorption

Root Hair Function

Root hairs are designed to increase the surface area for both the absorption of water and also nutrient mineral intake from the soil. It helps to absorb the water and minerals through osmosis.

Osmosis and Diffusion

Water enters root cells from high to low water potential through osmosis. The process of diffusion across cell membranes is termed the movement of nutrients and other solutes.

Water Movement Through Xylem

Cohesion-Tension Theory

Water molecules exhibit cohesion, thereby sticking to one another, and adhesion, thereby sticking to xylem walls, forming a continuous column of water moving upwards due to tension created by transpiration.

Capillary Action

The rise of water up through the narrow xylem vessels is occasioned by the combined effects of cohesion and adhesion.

Transpiration Pull

Water evaporates through the stomata of the leaf; this creates negative pressure that pulls more water up from the roots through the xylem.

Stomata And Transpiration

Structure and Function of Stomata

Small leaf surface pores controlled by guard cells; regulate gas exchange and the loss of water vapors

Factors Affecting Transpiration Rate

Light intensity, temperature, humidity, and wind. Generally, light intensity increases the temperature which raises the rate of transpiration, and high humidity with low wind reduces it.

Role in Water Regulation

It regulates the water balance of plants, cools the plant, and the suction force that it pulls helps in the upward flow of nutrients by pulling up water through the xylem.