What is Available Water in Plants?

Water is a crucial component for plant growth and sustenance. It is required for many biological processes, such as photosynthesis, transpiration, turgor pressure maintenance, and nutrient uptake. However, not all water that is present in the soil is available to plants. Available water in plants refers to the amount of water that can be easily absorbed by the roots and used for growth and metabolic activities.

Soil Water Potential

The availability of soil water for plants depends on the soil water potential. Soil water potential is the measure of the energy status of water in the soil. It is influenced by factors such as soil texture, structure, compaction, organic matter content, temperature, and salinity. Soil particles exert a force on the surrounding water molecules, which creates a tension that affects the ability of plants to extract water from the soil.

Water Holding Capacity

The water holding capacity of the soil also affects available water in plants. Water holding capacity is the amount of water that a soil can hold at field capacity, which is the maximum amount of water a soil can hold against gravity. It depends on the soil's porosity, bulk density, and organic matter content. Soils with high water holding capacity are able to retain more water for plant use, while soils with low water holding capacity require frequent watering.

Rooting Depth

The rooting depth of plants influences their ability to access available water in the soil. Plants with deep roots can reach greater amounts of water, while plants with shallow roots are limited to the surface soils. Root depth is determined by factors such as soil type, texture, structure, and nutrient content, as well as the species and age of the plant.

Drought Resistance Mechanisms

Plants have developed various drought resistance mechanisms to cope with limited available water. These mechanisms include the production of osmoprotectants, which are solutes that protect cells from water loss by maintaining turgor pressure, and the closure of stomata, which reduces water loss through transpiration. Some plants have also evolved to have shallow roots that spread widely to capture water during rainy periods and to be dormant during periods of drought.

Conclusion

In conclusion, available water in plants is the amount of water that can be easily absorbed by the roots and used for growth and metabolic activities. The availability of water in the soil for plants depends on factors such as soil water potential, water holding capacity, and rooting depth. Understanding these factors is essential for optimizing plant growth and productivity in a variety of soil and environmental conditions.