Effects of Day-length and Gibberellic Acid (GA3) on Flowering and Endogenous Hormone Levels in Rhynchostylis gigantea (Lindl.) Ridl.


  •  B. Phengphachanh    
  •  D. Naphrom    
  •  W. Bundithya    
  •  N. Potapohn    

Abstract

Effects of day-length and GA3 on flowering and endogenous hormone levels during flowering process of Rhynchostylis gigantea (Lindl.) Ridl. were studied. Three-year-old plants were grown under natural condition and short-day (10 h of light) combined with GA3 at 0 and 3,000 ppm, for 3 months. The results revealed that short-day could induce flower faster than natural condition around two weeks. Short-day and natural condition had effects on stem height and bush width, while GA3 had effects only on number of leaves per plant. ABA in leaf seemed to decreased in all treatments accept under NC-GA3, there was a peak of ABA at 30 days. Furthermore, under SD, GA3 seemed to decrease ABA in leaf. In shoot, ABA concentration was increased during 0-30 days in all treatments, after that GA3 seemed to decrease ABA concentration under NC, while the ABA concentration kept constancy under SD. On the other hand, GA3 seemed to boot t-ZR up in leaf under SD, but did not in shoot, where GA3 seemed to drop t-ZR. The reducing ABA and increasing t-ZR in leaf and/ or shoot might be related to flower buds initiation and early flowering of R. gigantea, especially, under SD.



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