PLANT PHYSIOLOGY , Vol 104, Issue 2 515-520, Copyright © 1994 by American Society of Plant Biologists
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METABOLISM AND ENZYMOLOGY |
Carbohydrate Status of Tulip Bulbs during Cold-Induced Flower Stalk Elongation and Flowering
H. Lambrechts, F. Rook and C. Kolloffel
University of Utrecht, Department of Plant Ecology and Evolutionary Biology, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands
The effect of a cold treatment on the carbohydrate status of the scales and
flower stalk of Tulipa gesneriana L. cv Apeldoorn bulbs during growth after
planting was studied and compared with bulbs not given cold treatment.
Bulbs were stored dry for 12 weeks at 5[deg]C (precooled) or 17[deg]C
(noncooled). Only the 5[deg]C treatment led to rapid flower stalk
elongation and flowering following planting at higher temperatures.
Precooling enhanced mobilization of starch, fructans, and sucrose in the
scales. The cold-stimulated starch breakdown was initially accompanied by
increased [alpha]-amylase activity per scale. In noncooled bulbs,
[alpha]-amylase activity slightly decreased or remained more or less
constant. Cold-induced flower stalk elongation was partially accompanied by
a decrease in the sucrose content and an increase in the glucose content
and invertase activity per g dry weight. The starch content in internodes
initially decreased and subsequently increased; [alpha]-amylase activity
per g dry weight of the lowermost internode showed a peak pattern during
starch breakdown and increased thereafter. The internodes of noncooled
bulbs, on the contrary, accumulated sucrose. Their glucose content and
invertase activity per g dry weight remained low. Starch breakdown was not
found and [alpha]-amylase activity per g dry weight of the lowermost
internode remained at a low level. Precooling of tulip bulbs thus favors
reserve mobilization in the scales and flower stalk and glucose
accumulation in the elongating internodes.
