Resource allocation in kiwifruit (Actinidia chinensis) : a thesis presented in partial fulfilment of the requirements for the degree Doctor of Philosophy in Plant Physiology at Massey University, Albany, New Zealand
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Date
2012
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Massey University
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Abstract
Kiwifruit growers in New Zealand receive financial incentives to produce high yields of fruit
with high individual dry matter concentrations (DMCs). Several vine management techniques
are available to growers to enable them to direct more resources into production of fruit rather
than into other sinks such as root growth and shoot extension. The long term consequences of
these management techniques are not well understood. The overall objective of the work
described in this thesis was to investigate how manipulating whole vine source-sink
relationships affects fruit quality, long-term vine health and productivity in ‘Hort16A’
kiwifruit vines.
A compensatory reduction in flower numbers occurred as a result of whole vine carbohydrate
depletion (famine treatment) and producing high crop loads of high DMC fruit with reduced
leaf area (minimal pruning, standard nitrogen). Keeping crop loads low did not result in
increased productivity, instead additional resources were allocated to root growth (feast
treatment). Isolating the canopy from the roots by extended trunk girdling was the technique
that enabled high flower numbers to be maintained across seasons.
Increasing individual fruit DMC generally enabled fruit to be harvested earlier than fruit with
lower DMC. This was because flesh colour change, the main harvest criterion, occurred
earlier in fruit from treatments where DMC was increased. Fruit softening behaviour was less
affected by changes in DMC than flesh colour change, meaning that low DMC fruit could be
softer at commercial harvest that more mature high DM fruit. The implications of this finding
for storage performance were discussed.
Vines showed few of the common responses to carbohydrate depletion. There was no
evidence of increased individual leaf area, reduced specific leaf weight, upregulated leaf
photosynthesis or increased shoot growth. Uptake and allocation of some mineral nutrients
within the vines was affected, but few visible signs of leaf nutrient deficiencies were seen.
The results suggest that vines respond to carbon depletion primarily be altering resource
allocation between flowering and root growth, rather than by altering its ability to capture
carbon.
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Keywords
Kiwifruit, Actinidia chinensis, Kiwifruit growth, Kiwifruit yield, Kiwifruit physiology