Effect of growth regulators, girdling, and mulching on flowering of young European and Japanese larches under field conditions

Abstract

Two experiments were undertaken in 1977 and 1979 to promote flowering of 5- and 7-ycar-old field-grown seedlings of Larixleptolepis Gord. and L. decidua Mill. A gibbcrellin A4/7 mixture (GA4/7) was applied alone or in combination with GA3 and naphthalene acetic acid (NAA) to both girdled and nongirdled trees or branches by two methods, perfusion into the xylem and spraying with an aqueous cationic surfactant solution. Perfusion was most effective, especially on girdled branches, although spraying was reasonably effective for male flowering in L. decidua. Only GA4/7 alone significantly increased flowering. Male flowering was doubled and female flowering increased eightfold by GA4/7 in the best treatments, over all application dates. Generally, male flowering doubled and female flowering increased eightfold by GA4/7. Even more flowering was obtained at optimal application dates. May and June applications were best, especially for treatments associated with girdling. However, some flowering occurred with applications as late as August and September. More strobili of both sexes develop in the upper crown. However GA4/7 treatment induced seed cone buds to appear in the lower crown, an abnormal location. An unusual effect occurred in that a positive flowering response of the 1977 experiment occurred only in 1979, whereas the 1979 experiment yielded enhanced flowering in 1980. Soil mulching with a plastic film, with or without hormone treatment, was a very effective adjunct treatment for both male and female flowering.

Carry-over effect of gibberellins (GA4/7) and ringing on female flowering in Norway spruce (Picea abies (L) Karst) seedlings

“…Using gibberellins (GA 4/7 ) and girdling he noticed a carry-over effect, observing flowering 2 years after the treatment (BonnetMasimbert, 1987). Similar results concerning a carry-over effect were obtained for Japanese and European larch grafts (Heitmüller and Melchior, 1960;Melchior, 1960;Bonnet-Masimbert, 1982), Douglas-fir seedlings (Pharis et al, 1980), Sitka spruce grafts (Philipson, 1985) and Engelmannwhite spruce grafts (Ross, 1992).…”

“…The effect in the second year after treatment has usually been attributed to girdling and/or strangulation alone (Heitmüller and Melchior, 1960;Melchior, 1960;Ross, 1992), or to the interaction of GA 4/7 and girdling (Pharis et al, 1980;Bonnet-Masimbert, 1982Philipson, 1985). This is the first time when the carry-over effect appeared also as a result of GA 4/7 alone.…”

Cytokinins in Vegetative and Reproductive Buds of Pseudotsuga menziesii

“…Franco) and variability in annual cone production impede breeding programs (12). Cultural practices to enhance cone production have included stem girdling (16,22), root pruning, temperature stress ( 15), nitrate fertilization ( 17), and even root flooding (2). Unfortunately, these methods have a limited effect on cone production and often damage the trees.…”

Shoot elongation, leaf demography and bud formation in relation to branch position on Larix laricina saplings

“…Bonnet-Masimbert 1982). It can be interpreted as a mechanism that (1) provides initial advantage in leaf expansion to the weaker short shoots lower in the crown that will experience progressive increases in shading thereafter and (2) exposes more slowly the peripherally situated long shoots that would be more demanding in terms of compensatory growth for crown spread if damaged by late frosts.…”