Different responses to different compositions of iso-osmotic salt solutions and to both osmotic agents indicate specific ionic effects. This study demonstrates that the germination of P. strombulifera is strongly influenced by the nature of the ions in the salt solutions and their interactions. Comparative studies of Cl(-) and SO(4)(2-) effects and the interaction between SO(4)(2-) and Cl(-) in salt mixtures indicate that extrapolation of results obtained with monosaline solutions in the laboratory to field conditions can be speculative.

Water stress is one of the most important environmental factors that regulate a plant's growth and development. In agronomic practice the effects of water stress are translated into low yield and/or reduced quality. Abscisic acid (ABA) sprays (1 mM) were applied to wheat plants at different phenological stages and the effects on several physiological variables and on yield were evaluated under field conditions at different water regimes. Studies were conducted in the field across three consecutive winter-spring seasons. ABA treatments were applied at the beginning of shoot enlargement and repeated at anthesis. Exogenous ABA increased shoot dry weight and maintained a high concentration of photosynthetic pigments for a longer period of time during grain growth and maturation. Although ABA applications increased stomatal closure immediately after its application, the longer-term effect was to allow for a greater ostiolar opening of the stomatal pore which resulted in increased conductance of gases and water vapor. ABA also improved the transport of photoassimilates from the leaves and stem to the developing grains, that is, it effectively increased the sink strength of the grains. This correlated with a yield increase without significantly changing the protein quality in the grains. Thus, elevated ABA levels from exogenous application or genetic selection could help improve agricultural production of grains in arid areas where irrigation is not possible.

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Seedlings of Prosopis strombulifera (Lam.) Benth. were grown hydroponically in Hoagland's solution with addition of 25 mmol/L NaCl every 48 h until final salt concentrations of 250, 500, and 700 mmol/L were reached. Control plants were grown without salt. Salinity induced anatomical changes in roots (young and mature zones), hypocotyls, young stems, and leaflets. The diameters of the young zone of roots of plants grown in increasing salt concentrations were smaller than those of controls, with reduced number of cortex layers and reduced size of the vascular system. The roots from tolerant plants showed precocious suberization and (or) lignification of the endodermal cells and early activity of the pericycle. Hypocotyl diameter was reduced along with a reduction in secondary phloem. Roots and hypocotyls showed abundant phellem formation. The stem diameter of young tolerant plants was notably diminished and less tissue lignification occurred. In stems and leaflets of treated plants, NaCl stimulated the production of tannins. In the leaflets, vascular bundles were similar in size. Groups of elongated parenchyma cells with many chloro plasts surrounded the bundles. These results suggest that in the absence of secretory organs, the anatomical modifications in this species are related to metabolic adaptations, such as an early development of the endodermal barrier for ion exclusion, to allow survival in high salinity.Key words: Prosopis strombulifera, anatomical changes, hydroponics, NaCl.

Anatomical changes in the peach (Prunus persica (L.) Batsch.) flower buds were defined and then assessed and correlated with the phenological stage from early dormancy through to flower opening. The peach flower bud, unlike the vegetative bud, shows a continuous anatomical development during the late autumn and winter dormancy period, even though there are no obvious macroscopic changes. Sterile whorls differentiate rapidly in late summer through early autumn. In contrast, fertile whorls develop very slowly during winter; their rapid development begins in late winter and continues through early spring. The androecium develops throughout the winter, while the gynoecium develops in late winter. By late winter, the anthers begin to undergo microsporogenesis and microgametogenesis and the ovaries have formed ovules. Vascular connections between flower primordia and branch wood are complete by late winter, when rapid phenological changes begin. At this point in time, the peach floral bud enters a "rapid maturation phase" that ends in flower opening. Thus, for the peach flower bud at least, the concept of dormancy as "a temporary suspension of visible growth of any plant structure containing a meristem" that was proposed by earlier researchers appears inappropriate. Rather, cell division, enlargement, and differentiation, which lead to organogenesis, take place throughout the entire "dormancy" period.Key words: dormancy, floral bud anatomy, floral bud phenology, peach, Prunus persica.