Relationship between gibberellin A_4/7 concentration, time of treatment, and crown position on flowering of Piceaglauca

Abstract

Treatment with the gibberellin mixture A4 and A7 (GA4/7) enhanced female flowering on mature white spruce (Piceaglauca (Moench) Voss). Time of treatment, crown position, and GA4/7 concentration influenced treatment success. GA4/7 treatment initiated before meristematic differentiation began (late June) enhanced female strobilus production, whereas those initiated after late June were ineffective. Shoots treated with 250 mg•L−1 GA4/7 bore significantly more female strobili than shoots that received 500 mg•L−1. Treatment did not affect female production on uppermost crown positions, male strobilus production, or seed yield per cone. Female strobili predominated from axillary buds centrally located on untreated shoots. GA4/7 treatments that enhanced female production shifted the distribution of strobili to more distal shoot positions.

Location of cones in the crown and along shoots of Sitka spruce (Picea sitchensis (Bong.) Carr.) and the influence of coning intensity and shoot size

“…On both the cuttings and mature trees in this study, female cones were most numerous on whorls 2 and 3. This is also in agreement with other work on single-age material (Marquard and Hanover 1984a;Philipson 1985;Bonnet-Masimbert 1987), though both whorls 1 and 4 have been found favourable Note: Values for shoot volume are mean, with SE given in parentheses. n, number of shoots measured in each section from 18 trees; T, terminal position; DL, lateral position on distal 20% of bearing shoot; ML, lateral position on adjacent 40% of bearing shoot; PL, lateral position on proximal 40% of bearing shoot.…”

“…In addition, where female and male cones occurred together on equivalent shoot types, male cones tended to be borne more proximally on the bearing shoots than female cones. These patterns fit those described elsewhere for this and other species of Picea Molder 1976, 1977;Powell 1983;Marquard and Hanover 1984a;Longman 1985;Longman and Dick 1985;Lüscher 1989) and indeed match remarkably those presented for P. mariana at a comparable level of detail (Caron and Powell 1993).…”

“…In both the juvenile cuttings and mature trees most cones were held in the upper whorls and interwhorl when few cones were borne but progressed basipetally (and centripetally) as total cone production increased. This general pattern has been noted in other even-aged material (Tompsett et al 1980;Marquard and Hanover 1984a;Dick et al 1994) and, to a great extent, mirrors the progression of the female zone in young P. mariana as they aged (and produced more cones; Caron and Powell 1992).…”

Influences of crown size and maturation on flower production and sex expression in Picea glauca treated with gibberellin A4/7

“…In white spruce (Picea glauca (Moench) Voss), GA 4/7 used alone or in combination with cultural treatments (heat stress and root pruning) promotes flowering of containerized grafts (Corriveau et al 1989, Greenwood et al 1991, Ross 1991, field-grown grafts (Cecich 1985, Daoust et al 1993a) and mature trees (Pharis et al 1986, Daoust et al 1993b. However, there is no evidence that the timing of GA treatment preferentially promotes male or female flowering in different stock types or that the concentration of GA applied affects the sex ratio (Owens and Molder 1979, Marquard and Hanover 1984a, 1984b, Cecich 1985, Pharis et al 1986.…”

Gibberellin A4/7enhances flowering of Picea glauca grafts in two consecutive years

“…The mixture of gibberellins A 4 and A 7 (GA 4;7 ) can increase flowering in conifers if applied at the correct time, duration and concentration (Cecich, 1983;Marquard and Hanover, 1984;Pollard and Portlock, 1983 …”