Hoe gebruik bome water?

All fruit farmers know that irrigation is an essential part of growing the perfect crop, but how do trees actually use water?

In order for photosynthesis to take place, plants need to take up carbon dioxide through the leaf’s very small openings. These openings on the leaf surface called stomata or Huidmondjies.

The stomata’s space is saturated with water vapour while the air outside of the leaf is generally not saturated during the day. Due to the difference in vapour pressure in the air outside the leaf and the vapour pressure inside the leaf, water moves out of the leaf while the stomata are open. This process is called transpiration.

There is a compromise between plant productivity and water lost through transpiration. Stomata can close partially or fully in order to manage water loss through transpiration, but this impacts on the uptake of carbon dioxide, which may again impact on dry matter production, i.e. fruit growth, sugar levels, vegetative growth, sugar and metabolite production, energy for various processes, etc.

Factors that affect the water vapour pressure in the air can affect the rate of transpiration.

• Low relative humidity at high temperature equates to a low air water vapour pressure and therefore a strong driving force for transpiration.
• Wind removes the more saturated layer of air in immediate contact with the leaf and therefore also increases transpiration.
• Nets can increase the water vapour pressure of the orchard air and decreases wind, thereby decreasing the driving force for transpiration.

What happens when plant’s water supply is insufficient?

The water in the plant can become under considerable tension on days of high transpiration when supply to leaves through the roots and stem cannot keep up with the demand. The plant finds it more difficult to access soil water as the soil dries out. At a certain soil water moisture level, the plant cannot take up any water. Due to limitations to the rate at which water can flow through the plant, water demand can outstrip supply even when the  soil contains enough water. Partial to full closure of stomata at this point can restrict transpiration, but will limit photosynthesis due to lower uptake of carbon dioxide.

Sufficient water supply vary from crop to crop see our products page for more information.