Assist. Prof. Dr. Waleed A. T. El-Fahdawi

Many environmental stresses affect the growth and yield of all plants, and the most important environmental stress is the water stress, which is in contact with the nature of the growth of most parts of the plant, especially the roots, which we will focus in this article on the relationship of its growth and development with water stress and its reflection on plant growth. Studying the root state and the nature of its response to water stress conditions enables us to study the entire plant functions and the disturbance that occurs under stress.

The root of the plant is hidden in the soil, far from the view of the breeder, and it is rarely linked positively and negatively in its characteristics with the state of the plant’s tolerance to salt or water stress, and thus we find only a few researchers who based the selection of stress-tolerant plants on some root characteristics, , This is mainly due to the fact that the available scientific concepts about the characteristics of the root under stress are still not understood in the scientific way that makes the breeder rely on them in the selection programs.

The division of root cells horizontally and vertically in the soil and its relationship to plant growth in the later stages and the yield, is also still unclear in terms of functions as a basis for most of the different field plants.

Perhaps the corn plant is of the most interest by researchers in genetic research and breeding processes, as well as studying the state of the root, its growth and other characteristics and its relationship with plants of the later generation, where the difference in the size of the root in water-sufficiency and non-water-sufficiency soil, but will this size be the same if the root is exposed to stress or will it be larger?

The growth of the root, as well as other parts of the plant, is controlled by several hormones, such as ABA, and this acid, if added to the plant, would reduce its growth, as the plants that grow under water stress have a high concentration of ABA.

This conclusion is in agreement with the results of several researchers, as this mechanism may be associated with an increase in the concentration of ethylene in the part exposed to water stress, The limiting factor for plant growth could be ethylene, which is present with ABA. Therefore, scientists confirmed that the characteristic of large root size is associated with the presence of genes responsible for the high concentration of ABA. If this fact applied to all plants, it would have been possible to benefit from it in breeding programs. It was found through the results of the research that the roots of corn plant grown in the dark and under a temperature of 29° and an ET value reached zero, the root tip growth was at a rate of 3 Mm per hour, knowing that it was planted in a media of water-sufficient vermiculite, While it grew at a rate of 4 Mm per hour when the seedlings were in the media of a nutrient solution. In general, root growth is a non-specific condition as long as there are soil conditions and a suitable climate for growth, as the roots go deep into the depths of the soil, it may reach several meters. It also spreads horizontally under the same growth conditions, while its growth is determined to a large extent under the opposite growth conditions. For example, it was found that the roots of corn had grown to a depth of about 2.5 Mm in light soil under adequate irrigation, while the root of this crop plant grew at a rate of one mm in The hour when it was growing under water stress at a rate of -1.6 MPa.

The growth factors associated with the root growth of a specific plant makes the division and elongation of root cells associated with these factors, especially the root tip, which is the basis for the rate of root growth and spread.