Effects of gibberellin A4/7, 6-benzylaminopurine and chlormequat chloride on the number of male and female strobili and immature cones in Chinese pine (Pinus tabuliformis) with foliar sprays

Abstract

Three kinds of plant growth regulators, gibberellinA4/7 (GA4/7), 6-benzylaminopurine (BA), and chlormequat chloride (CCC), were evaluated for their ability to promote strobilus and cone production in a Chinese pine (Pinus tabuliformis Carr.) clonal seed orchard. Treatments (0, 250, 500, or 1000 mg·L−1) were applied during three periods (June–July, July–August and August–September) in 2005. Of the three plant growth regulators, GA4/7 was the best for promoting flower and cone production. Trees sprayed with GA4/7 (500 mg·L−1) from June to September had significantly more female strobili and immature cones than controls and other treatments (p≤0.0001). The best time to apply GA4/7 was in June. BA at 500 mg·L−1 significantly increased female flower and immature cone production, compared to other treatments and controls (p≤0.0001), while promotion of male strobili was unchanged. Chlormequat chloride at 1000 mg·L−1 significantly increased the number of male strobili, compared to the other treatments (p≤0.0001). Spraying CCC at 500 mg·L−1 significantly increased the number of female strobili, compared to controls (p 0.05). These results are important for improving seed production and seed orchard management of Chinese pine.