Articles
Xylem uptake and mobilisation of exogenous sucrose in dormant kiwifruit canes
Article number
1419_12
Pages
87 – 94
Language
English
Abstract
During winter chilling in kiwifruit (Actinidia sp.), starch in plant tissues is hydrolysed into soluble sugars that function to enhance freezing tolerance.
It is possible that under low chilling conditions there is a paucity of soluble sugar availability to support the metabolism of dormant buds.
In the xylem, vessel-associated cells release and absorb sugars from the apoplast even during dormancy in deciduous species.
Dormancy is maintained via hormones within buds, but sufficient sucrose availability can interact with hormone networks to trigger bud break.
We hypothesized that exogenous sucrose perfused via the xylem may simulate high chill accumulation, leading to higher budbreak and flower production even under low chill conditions.
To test this, we excised Actinidia chinensis var. deliciosa LSQUOHaywardRSQUO canes in early winter after 150 h of chill accumulation.
High chill control canes were placed into cool storage to accumulate 1200 total chill hours.
Low chill control canes and perfusion treatment canes received no additional chill.
Perfusion treatments consisted of a range of sucrose concentrations (0-15% w/v), which were repeated three times over four weeks.
Bark and wood carbohydrate concentrations were quantified before and after treatments, and canes were assessed for budbreak and flower production.
Canes perfused with sucrose solutions had increased wood and bark starch and sucrose concentrations but had lower concentrations of raffinose and stachyose than high-chill control canes.
Budbreak and flower production were not increased in perfused canes compared with low-chill controls.
These results demonstrate that kiwifruit canes are capable of absorbing and metabolising exogenous sucrose perfused via the xylem, even at unnaturally high concentrations.
However, the increased availability of sugar was not a sufficient substitute for winter chilling to drive higher productivity in spring.
It is possible that under low chilling conditions there is a paucity of soluble sugar availability to support the metabolism of dormant buds.
In the xylem, vessel-associated cells release and absorb sugars from the apoplast even during dormancy in deciduous species.
Dormancy is maintained via hormones within buds, but sufficient sucrose availability can interact with hormone networks to trigger bud break.
We hypothesized that exogenous sucrose perfused via the xylem may simulate high chill accumulation, leading to higher budbreak and flower production even under low chill conditions.
To test this, we excised Actinidia chinensis var. deliciosa LSQUOHaywardRSQUO canes in early winter after 150 h of chill accumulation.
High chill control canes were placed into cool storage to accumulate 1200 total chill hours.
Low chill control canes and perfusion treatment canes received no additional chill.
Perfusion treatments consisted of a range of sucrose concentrations (0-15% w/v), which were repeated three times over four weeks.
Bark and wood carbohydrate concentrations were quantified before and after treatments, and canes were assessed for budbreak and flower production.
Canes perfused with sucrose solutions had increased wood and bark starch and sucrose concentrations but had lower concentrations of raffinose and stachyose than high-chill control canes.
Budbreak and flower production were not increased in perfused canes compared with low-chill controls.
These results demonstrate that kiwifruit canes are capable of absorbing and metabolising exogenous sucrose perfused via the xylem, even at unnaturally high concentrations.
However, the increased availability of sugar was not a sufficient substitute for winter chilling to drive higher productivity in spring.
Publication
Authors
K. Kramer-Walter, M. Clearwater, N. Gould, A. Richardson, H. Boldingh
Keywords
kiwifruit, winter chilling, dormancy, exogenous sucrose, xylem sugar uptake
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