ABSTRACT
Three closely related growth regulators (G) that are present in some myrtaceous plants were examined for possible anti-transpirant effects. The bioassay material involved cuttings of mung bean and Eucalyptus rupicola. Stomatal resistance was determined by a diffusion porometer. Water loss was equated with water uptake by the cutting over a 24-hour period.In both bioassays, G reduced water loss. The reduced water loss was associated with stomatal closure. This anti-transpirant effect of G was five to ten times less than that of abscisic acid. The stomatal resistance to the diffusion of water vapor from mung bean leaves increased within 1 hour of application of G. Marked stomatal closure occurred after 6 hours when 5 to 7 micrograms of G had accumulated in the leaves.These results and earlier evidence, suggest that G growth regulators are involved in the water economy of Eucalyptus and perhaps other related genera.
ABSTRACT
A growth regulator (G) occurs at high concentrations in adult leaves of E. grandis Maiden. Low concentrations of G are present in juvenile leaves of this species and also in adult leaves of some other Myrtaceae. Low concentrations of G (5×10(-6) and 10(-5) M) promote rooting in mung-bean cuttings and elongation in Avena coleoptile sections; high concentrations (5×10(-4) M) inhibit. These and other bioassay results indicate that G may have auxin-like activity.
ABSTRACT
Interspecific compatibility and incompatibility have been examined through the genus Populus. General methods of manipulation have been developed to break the incompatibility barriers. These methods are described and a hypothesis is put forward to account for the results. This proposes that at least two factors are involved, one attached to the pollen (P) and one to the stigma (S), and that the interaction of these (PS) is critically involved in the total process. Implications for future plant breeding are discussed.
