Phenology, Pigment Content and Diurnal Change of Proline in Green and Senescing Leaves of Three Zygophyllum Species

Abstract

Phenology, pigment content, succulence ratio and the diurnal changes of water and proline contents were investigated in green and yellow leaf parts of Zygophyllum album , Z. decumbens and Z. coccineum . Phenological patterns and the leaf area index were followed monthly during 1988. Pigment content, succulence ratio and the diurnal change of water and proline contents were investigated under natural environments in August. The leaf area index curves of the three species showed the highest values towards the end of the rainy season. The yellow leaflets and petioles of Z. album showed higher fresh and dry weights than the corresponding green ones. On the contrary, the green leaflets and petioles of Z. decumbens and Z. coccineum showed higher fresh and dry weights than the yellow ones. With the exception of shrivelled leaflets of Z. album , the leaf parts of the species investigated showed high succulence ratio. Phenology and the pigment content results support the concept that the three species undergo leaf senescence followed by shedding in the dry season. The importance of chlorophyll-dependent proline biosynthesis was clarified. The petioles of Z. decumbens and Z. coccineum showed higher proline content than the leaflets. Most leaf parts of the investigated species showed diurnal change of water and proline contents. Irrespective of the species, the relationship was negatively correlated in the green leaflets, the green and yellow petioles. This implies that the three species, although from two different habitats, showed a confirmed generality of proline accumulation, but in different magnitudes by the green and yellow (senescing) leaf parts as a response to water deficit.