Low air humidity increases leaf-specific hydraulic conductance of Arabidopsis thaliana (L.) Heynh (Brassicaceae).

The typical isohydric plant response to low relative humidity involves stomatal closure, followed by long-term responses like adjustment of shoot-to-root ratios. Little information is available on the early responses of the root system to exposure of shoots to low humidity, nor is it clear to what extent responses of Arabidopsis thaliana conform to the isohydric model. In this study, A. thaliana plants grown hydroponically at high humidity were exposed to two constant relative humidities, 17% and 77%, while the root system remained in aerated nutrient solution. Leaf conductance (g(s)), transpiration, water potential (Psi(l)), osmotic potential, and whole plant hydraulic conductance (K) were determined for the following time intervals: 0-10, 10-20, and 20-40 min, and 0-5, 5-10, and 24-29 h. At low relative humidity, no change in g(s) was detected. Psi(l) decreased by 0.28 MPa during the first 5 h and then remained stable. During the first hour, leaf-specific K averaged 1.6 x 10(-5) kg MPa(-1) m(-2) s(-1) at high humidity. At low humidity it increased >3-fold to 5.8 x 10(-5) kg MPa(-1) m(-2) s(-1). Similar significant differences in K were observed during all time periods. Low concentration mercury amendments in the hydroponic solution (5 microM and 10 microM HgCl(2)) had no discernible influence, but pre-exposure to 50 microM HgCl(2) reduced K differences between humidity treatments. As HgCl(2) is known to be a potent inhibitor of aquaporin function, this suggests that aquaporins may have played a role in the fast hydraulic response of plants transferred to low humidity. The rapid hydraulic response and the influence of mercury raise the possibility that an alternative response to atmospheric dryness is increased K modulated by aquaporins.

Microcutting culture and morpho-physiological changes during acclimation in two Lycium chilense cytotypes

Lycium chilense, a deciduous perennial shrub, is one of the endangered native species of Patagonia due to sheep overgrazing. Chances of recolonization by seeds are scarce due to the limited density of propagules in the soil and very specific requirements for germination. The objective was to develop an in vitro propagation protocol that would help to perform reestablishment of this species in degraded areas of the Patagonian steppe. Seeds came from two provenances with different somatic number due to differences in ploidy level. Defoliated microcuttings were planted in test tubes with different growing media and taken to a growth chamber. Rooting percentage did not differ between origins, but higher values were encountered for medium without hormones. Subcultures increased significantly rooting percentage and reduced time to rooting. The leaves from micropropagated plants were thinner, did not exhibit hairs, and had poorly developed palisade parenchyma and less epicuticular waxes. In vitro leaves had lower stomatal density and their stomata were less functional when compared to acclimated leaves. A repopulation program of Lycium chilense based on microcutting culture, specialy using subcultures, is feasible. (AU)

Microcutting culture and morpho-physiological changes during acclimation in two Lycium chilense cytotypes

Lycium chilense, a deciduous perennial shrub, is one of the endangered native species of Patagonia due to sheep overgrazing. Chances of recolonization by seeds are scarce due to the limited density of propagules in the soil and very specific requirements for germination. The objective was to develop an in vitro propagation protocol that would help to perform reestablishment of this species in degraded areas of the Patagonian steppe. Seeds came from two provenances with different somatic number due to differences in ploidy level. Defoliated microcuttings were planted in test tubes with different growing media and taken to a growth chamber. Rooting percentage did not differ between origins, but higher values were encountered for medium without hormones. Subcultures increased significantly rooting percentage and reduced time to rooting. The leaves from micropropagated plants were thinner, did not exhibit hairs, and had poorly developed palisade parenchyma and less epicuticular waxes. In vitro leaves had lower stomatal density and their stomata were less functional when compared to acclimated leaves. A repopulation program of Lycium chilense based on microcutting culture, specialy using subcultures, is feasible.

Microcutting culture and morpho-physiological changes during acclimation in two Lycium chilense cytotypes.

Lycium chilense, a deciduous perennial shrub, is one of the endangered native species of Patagonia due to sheep overgrazing. Chances of recolonization by seeds are scarce due to the limited density of propagules in the soil and very specific requirements for germination. The objective was to develop an in vitro propagation protocol that would help to perform reestablishment of this species in degraded areas of the Patagonian steppe. Seeds came from two provenances with different somatic number due to differences in ploidy level. Defoliated microcuttings were planted in test tubes with different growing media and taken to a growth chamber. Rooting percentage did not differ between origins, but higher values were encountered for medium without hormones. Subcultures increased significantly rooting percentage and reduced time to rooting. The leaves from micropropagated plants were thinner, did not exhibit hairs, and had poorly developed palisade parenchyma and less epicuticular waxes. In vitro leaves had lower stomatal density and their stomata were less functional when compared to acclimated leaves. A repopulation program of Lycium chilense based on microcutting culture, specially using subcultures, is feasible.

Microcutting culture and morpho-physiological changes during acclimation in two Lycium chilense cytotypes.

Lycium chilense, a deciduous perennial shrub, is one of the endangered native species of Patagonia due to sheep overgrazing. Chances of recolonization by seeds are scarce due to the limited density of propagules in the soil and very specific requirements for germination. The objective was to develop an in vitro propagation protocol that would help to perform reestablishment of this species in degraded areas of the Patagonian steppe. Seeds came from two provenances with different somatic number due to differences in ploidy level. Defoliated microcuttings were planted in test tubes with different growing media and taken to a growth chamber. Rooting percentage did not differ between origins, but higher values were encountered for medium without hormones. Subcultures increased significantly rooting percentage and reduced time to rooting. The leaves from micropropagated plants were thinner, did not exhibit hairs, and had poorly developed palisade parenchyma and less epicuticular waxes. In vitro leaves had lower stomatal density and their stomata were less functional when compared to acclimated leaves. A repopulation program of Lycium chilense based on microcutting culture, specially using subcultures, is feasible.