|Authors: ||X. Min, Duane P. Bartholomew|
Natural flowering of pineapple (Ananas comosus (L.) Merrill) can reduce yields and disrupt crop scheduling.
In an effort to better understand the mechanism(s) of flowering, pineapple tissue ethylene production and the effects of growth regulators on it were investigated.
Ethylene production (fresh weight basis) by basal white tissue of the youngest physiologically mature (D) leaf (basal tissue) ranged from 1.97 to 3.99 nl g-1 h-1; that produced by stem apical (stem) tissue ranged from 0.52 to 1.37 nl g-1 h-1. Ethylene was not detected from green leaf tissue.
Ethylene production by basal tissue was correlated (r = 0.74) with ethylene-forming enzyme (EFE) activity of that tissue but not with 1-aminocyclopropane-1-carboxylic acid (ACC) levels.
Ethylene production by stem tissue was more highly correlated with ACC level (r = 0.88) than with EFE activity (r = 0.21). Ethylene production by stem tissue and basal tissue were positively correlated (r = 0.64). Ethylene production by basal tissue was somewhat correlated with plant size (r = 0.44) while that of the stem was not.
EFE activity in leaf and stem tissue were not well related to plant size.
Ethylene production by stem tissue of ethephon treated plants was at least two-fold greater than the controls up to five days after treatment.
Stem tissue of plants treated with naphthaleneacetic acid (NAA) produced up to ten times more ethylene than did controls.
All plants treated with ethephon or NAA were induced to flower.
Ethylene production by stem tissue dipped in a solution containing 2.0 g l-1 gibberellic acid (GA3) was significantly lower than controls, but ethylene production by stem tissue of GA3 treated plants was not different from controls.
Ethylene production by stem tissue dipped in a solution containing amino-oxyacetic acid was significantly inhibited.
Dikegulac sodium, paclobutrazol and uniconazole had no effect on ethylene production or EFE activity of excised tissue dipped in solutions, or on treated intact plants.
GA3, dikegulac sodium, paclobutrazol, and uniconazole applied prior to forcing did not block ethephon induced flowering.
GA3 promoted peduncle elongation, but decreased inflorescence weight while plants treated with paclobutrazol and uniconazole had a shortened peduncle, but inflorescence weights that were comparable to the control.
Plants treated with silver thiosulfate (STS) followed by ethephon a week later were not forced.
The data indicate that ethylene plays a primary role in floral initiation and that GA3 may be involved in inflorescence development.
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