Fine Structural Changes in the Mesophyll Tissue of the Leaves of Xerophyta villosa during Desiccation

Abstract

X. villosa Th. Dur. and Schinz (Velloziaceae) is a desiccation-tolerant angiosperm that loses its chlorophyll under water stress. In the laboratory under controlled conditions, full desiccation takes 10-14 days. During drying, the leaves wilt slightly and yellow; leaf width is reduced to approximately, 1/2. After 8 days of drying, the chloroplast internal structure is reduced to stacks of elongate vesicles instead of grana and intergranal lamellae. Mitochondria lose their cristae. By 13 days, desiccation is complete; the only recognizable organelles are nuclei with dense chromatin and proplastid-like organelles containing vesicles and plastoglobuli.