The physiology and biochemistry of the multipurpose forest trees species: Leucaena leucocephala (Lam.) De Wit, Prosopis juliflora (Swartz) DC, Acacia saligna (Labill.), and Eucalyptus citriodora (Hook F.) as influenced by water stress
Abstract
This research was conducted to study the influence of water stress on four multipurpose forest trees species (MPFT): Leucaena leucocephala (Lam.), Prosopis juliflora (Swartz), Acacia saligna (Labill.), and Eucalyptus citriodora (Hook F.). Productivity as well as physiological and biochemical responses to drought were studied. Simulated annual rainfall amounts representing different rainfall distributions of arid and semi-arid regions, were applied in an initial greenhouse experiment to examine the species ability to survive and grow with variable available water. The four species produced forage across the range of available water even at the lowest levels. A. saligna and L. leucocephala produced the highest amounts of forage. Several traits were studied such as number of leaves and branches, leaf nitrogen (forage quality), plant height, and root nodulation. These traits tended to decrease as water applied decreased. In a second greenhouse experiment, two drought periods were applied to young sapling of the four study species with an intervening rewatering period. Drought significantly influenced physiological processes such as photosynthesis, stomatal conductance, and transpiration rate as well as leaf relative water content and water potential. P. juliflora and E. citriodora showed greater photosynthesis and higher leaf relative water content across the range of measured water stress compared to L. leucocephala and A. saligna. Withholding water induced the accumulation of proline in the three leguminous species and quaternary ammonium compounds (QAC) in P. juliflora. P. juliflora showed the highest accumulation of both proline and QAC. P. juliflora and E. citriodora were more efficient in photosynthesis under drought compared to the other species as judged by higher rates of assimilation per unit of leaf water potential. This shows the potential of both species to tolerate drought with continued physiological functioning. Solute accumulation may have influenced P. juliflora physiological activity under drought. However, E. citriodora showed no solute accumulation, although exhibited an efficient photosynthesis under water stress. As such, the relationship between biochemistry and physiology needs further study that can be important criteria in selecting plant species to grow in dry areas. Growing such species will support the agricultural systems and reforestation efforts in the arid and semiarid regions.
Degree
Ph.D.
Advisors
Gillespie, Purdue University.
Subject Area
Forestry|Botany
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