Water Relations of the Banana. III. Effects of Controlled Water Stress on Water Potential, Transpiration, Photosynthesis and Leaf Growth.

Abstract

Banana suckers were grown in the glasshouse under controlled environmental conditions. Water potentials were measured on plants 6-12 months old using the solute potential of the latex as a guide. The diurnal fluctuations in water potential were monitored along with measurements of transpiration rate, leaf conductance, leaf temperature, assimilation rate and leaf growth rate.

Concurrent measurements were made of water potential, transpiration and other gas exchange parameters under rapidly and slowly applied water stress. Stomatal closure was almost complete after 10 days of rapid stress whereas, under slow stress, closure was delayed for a total of 30 days. Stomatal closure was accompanied by a reduction in transpiration and photosynthesis. However, the water potential of the plant was never more negative than -0.35 MPa even when the water stress was severe. The growth of the plant, as evaluated from the emergence of new leaves, was stopped at the same time as photosynthesis. The implications of these observations on the ability of banana to utilise dwindling supplies of water are discussed. The use of latex solute potential as a tool to understand the water status of the plant is further explained.