ISSN: 0041-3216 (Online), 0041-3216 (Print)
Volume 63 Number 3
Decreased water transport in lethal yellowing-diseased coconut palms
Reports of decreased water transport in lethal yellowing diseased coconut palms were confirmed by demonstrating decreased translocation of 32P applied to roots, stems and petioles. Investigation of the sites of vascular dysfunction indicated that the rates of 32P uptake and xylem exudation from excised roots of diseased palms were 10% of such rates in comparable healthy palms. In addition, the rate of water flow in excised petioles of diseased palms was ? 44% of that of healthy palms. The near complete stomatal closure, even on turgid leaves, was the earliest detectable symptom of lethal yellowing. Stomatal closure was coupled with a vastly increased resistance to diffusion of water vapour from leaves; this is likely to be the primary factor affecting the decreased rate of water transport in lethal yellowing diseased palms.
Keywords: Mycoplasma-like organism; Stomatal closure; Xylem transport