Gibberellin A4/7 and the Promotion of Flowering in Pinus radiata

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Abstract
Gibberellin A4/7 mixture (GA4/7), a highly effective promoter of early and enhanced flowering in the Pinaceae, caused a significant reallocation of dry matter and 14C-photosynthate within terminal buds of Pinus radiata D. Don within 8 days of hormone treatment. Treatment with GA4/7 to terminal shoots of vigorous, potentially flowering mature grafted propagules reduced the flow of photoassimilated 14C and dry matter into the terminal bud as a whole, but significantly increased the dry matter and 14C allocated within the bud to developing long-shoot primordia (potential seed-cone buds). This was accomplished at the expense of the structural tissues, the apical dome region, and the vegetative branch buds. Although GA3 caused a similar reallocation of dry matter within the terminal bud, it was significantly less effective than GA4/7 thus appears to have, in addition to any nutrient diversion abilities, a distinct morphogenic function in sexual differentiation.