Abstract:
Objective Starch metabolism at time of repeated bolting was studied to determine the optimum time for bulb-harvesting in propagation of out-of-season lilies.
Method Contents of starch and reducing sugars as well as images of starch granules under scanning electron microscope of the lily bulbs at various developmental stages were examined. Expressions of amylase-related genes of the bulbs were obtained by qRT-PCR.
Result The starch and reducing sugars in the bulbs underwent significant changes at germination stage, as the starch content decreased by 4.98% and reducing sugars increased by 3.23%. The SEM images of the starch granules were of A-, B- and C-types, or, large, medium and small in sizes. They were mainly A- and B-types in the expanding and mature bulbs. Upon germinating, the granules began to separate from one another with the appearances of C-type and deformed A-type that showed depressions or were stretched to an L/S ratio as high as 1.77. At bolting, the A-type granules disappeared while the B- and C-types appeared with bubbles and tiny " bud-like” growth on their surfaces. The qRT-PCR analysis indicated that the AMY gene in the bulbs expressed at a high-level during germination and bolting stages, while SSS and SBE at expanding and mature stages, and that the variations paralleled the contents of starch and reducing sugars.
Conclusion A large amount of starch was consumed during repeated bolting of the bulbs. Thus, to reduce the ill-effects on the quality of the bulbs and lily flowers, bulb-harvesting at the mature stage was recommended.
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