Water Management in Horticultural Crops

4.Effect of moisture stress on crop growth

Water stress affects, particularly every aspect of plant growth: modifying anatomy, morphology, physiology and biochemistry. Some of the adverse effects of deficit soil moisture stress on plant growth, development and yield are:

• Loss of turgidity leading to cell enlargement and stunted growth
• Decrease in photosynthesis due to decreased diffusion of CO2 with the closure of stomata to conserve water and reduced leaf area.
• Increase in respiration resulting in decreased assimilation of photosynthates
• Break down of RNA, DNA and proteins
• Inhibition of synthesis and translocation of growth regulators
• Hydrolysis of carbohydrates and proteins leading to increase in soluble sugars and nitrogen compounds
• Affects germination, cell expansion, cell division, growth of leaves, stems ,fruits and root development. The duration of crop in general is increased when the stress occurs before flowering and decreased when occurs after flowering.
• The degree and duration of moisture stress at these stages finally dictates the economic yield. The dry matter, number of fruits and individual grain weight are affected.
• Delaying the first irrigation for some days after germination in order to impose some amount of water stress encourages deeper penetration of roots that enables the crops to explore water from deeper layers of soil and withstand drought conditions better.