The Effect of Abscisic Acid and Benzylaminopurine On Gases Exchange and Water Use Efficiency in Maize (Zea mays L.) During Water Stress.

Young plants of maize, cv. Anjou 245, exposed to gradual drying-up of soil retained a high RWC (84–89 %), virtually at the level of non-stressed plants, for 3 through 12 days after interruption of irrigation. However, the results confirmed that even in the C4 maize plants growing on a drying-up soil, there is a chemical signal by which the information on the drought is transferred to the above-ground part of the plant. This chemical signal is probably the abscisic acid (ABA) produced in roots and transported to leaves. The proof is that plants respond to the decreasing availability of water in soil by partially closing stomata and reducing the photosynthesis and transpiration rates in spite of the high relative water content in leaves. It was also found that growth regulators supplied to maize during a water stress can effectively influence its photosynthetic performance and water management capability. Reducing the gas exchange parameters by applying ABA can generally improve the ability of plants to survive an unfavourable drought because reduction of the amount of water evaporated through transpiration enables the plant to economise water, to adapt gradually as concerns osmosis and to redistribute water in its organs. Another aspect that apparently also matters are the interactions of exogenously supplied substances and the natural levels of hormones in plants, as shown by the findings obtained after application of benzylaminopurine (BAP). A lower dose of BAP ultimately supported the ability of maize plants to economise water and improved water use efficiency (WUE). A higher dose of BAP supported improvement of WUE by increasing the photosynthesis rate.