New Zealand Journal of Crop and Horticultural Science abstracts
Late-season temperature effects on the carbon economy and tree performance
of ‘Royal Gala’ apple (Malus domestica) trees
Dennis H. Greer*
The Horticulture and Food Research Institute
of New Zealand Ltd
Palmerston North Research Centre
Private Bag 11 030
Palmerston North, New Zealand
*Present address: School of Wine and Science, Charles Sturt University,
Locked Bag 588, Wagga Wagga, NSW 2678, Australia.
email: dgreer@csu.edu.au
Jens N. Wünsche
The Horticulture and Food Research Institute
of New Zealand Ltd
Hawke’s Bay Research Centre
Private Bag 1401
Havelock North, New Zealand
Abstract Potted ‘Royal Gala’ apple on M.9 rootstock
(Malus domestica) trees were grown after fruit harvest at constant
temperature conditions (18/8°C day/night) for 3, 6, and 9 weeks to manipulate
their carbohydrate reserves. On several occasions, leaf gas exchange was
measured and selected trees were destructively harvested before and after
each treatment to measure the dry weight of the component parts. Samples
were also taken for carbohydrate analysis. After treatment, the remaining
trees were returned outdoors and, in spring, selected trees from each treatment
were destructively harvested for dry weight and carbohydrate analysis. Budbreak
was then measured and fruit weight and crop load determined next autumn and
the trees destructively harvested for dry weight and carbohydrate analysis.
There was no change in tree dry weight after each late-season temperature
treatment. Carbohydrate concentrations, averaged over the whole tree, increased
by 10-15% compared to the pre-treatment trees, consistent with a net increase
in carbon acquisition. Over winter, the total carbohydrate concentration
had declined by 25-40%. In spring, time of budbreak differed significantly;
trees exposed for 3 weeks to 18/8°C in late-season broke buds 9-19 days
earlier than the other treatments in the following spring. The early budbreak
was associated with not only the largest increase in carbohydrate concentration
during treatment but also the greatest decrease thereafter. Although there
is some support for the conclusion that high carbohydrate reserves confer
a direct benefit on the budbreak process, it remains an open question if
it was the increase in reserves, or their subsequent consumption that advanced
budbreak.
Keywords budbreak; carbohydrates; fruit weight; crop
load; photosynthesis; respiration; carbon balance
H02089 Received 25 November 2002; accepted 31 March 2003; published 8
August 2003
New Zealand Journal of Crop and Horticultural Science, 2003, Vol. 31:
235-245
0014-0671/03/3103-0235 $7.00 © The Royal Society of New Zealand
2003
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