Articles
Rootstock-dependent physiological and biomass allocation responses of apple trees to water deficit
Article number
1468_27
Pages
207 – 212
Language
English
Abstract
Efficient water use in irrigated apple orchards is essential for sustaining yields and fruit quality in water-limited regions.
This study evaluated the effects of water deficit (WD) on whole-tree transpiration, leaf gas exchange, and biomass allocation in ‘Rosy Glow’ apple trees grafted onto five rootstocks: M.793, M.7, G.222, G.202, and M.9 RN.29 (in order of decreasing vigour). We tested the hypothesis that dwarfing rootstocks (e.g., M.9 RN.29) are more sensitive to WD. The trial was conducted outdoors in Stellenbosch, South Africa, in 2019, using potted one- and two-year-old trees.
Two WD cycles were imposed by completely withholding irrigation for 9 days (23 Feb-3 Mar) and 10 days (23 Mar-1 Apr). Whole-tree transpiration was measured with sap flow sensors and the stem heat balance method.
WD significantly reduced daily transpiration, net CO2 assimilation rate (A), stomatal conductance (gs), transpiration rate (E), chlorophyll a and b (chla, chlb), and the chla/chlb ratio, while increasing intrinsic water use efficiency (WUEi) across all rootstocks.
During recovery, M.793 and M.9 RN.29 trees exhibited rapid restoration of transpiration, while G.202, G.222, and M.7 recovered more slowly, suggesting potential adaptation responses.
In WD cycle 2, G.222 and M.9 RN.29 maintained higher A, maximum electron transport rate (Jmax), triose phosphate utilization (TPU), and maximum Rubisco carboxylation rate (Vcmax) compared to M.793, M.7, and G.202. Root biomass partitioning increased under WD for M.793 and G.222, but not for M.7, G.202, or M.9 RN.29. Trees on M.7, G.202, and M.9 RN.29 displayed a marked decrease in total dry mass accumulation in response to water deficit.
Results indicate that M.9 RN.29 is not more WD-sensitive than other rootstocks and can recover effectively.
These findings provide insights for rootstock selection and adapted irrigation scheduling to optimize water productivity under water-limited conditions.
This study evaluated the effects of water deficit (WD) on whole-tree transpiration, leaf gas exchange, and biomass allocation in ‘Rosy Glow’ apple trees grafted onto five rootstocks: M.793, M.7, G.222, G.202, and M.9 RN.29 (in order of decreasing vigour). We tested the hypothesis that dwarfing rootstocks (e.g., M.9 RN.29) are more sensitive to WD. The trial was conducted outdoors in Stellenbosch, South Africa, in 2019, using potted one- and two-year-old trees.
Two WD cycles were imposed by completely withholding irrigation for 9 days (23 Feb-3 Mar) and 10 days (23 Mar-1 Apr). Whole-tree transpiration was measured with sap flow sensors and the stem heat balance method.
WD significantly reduced daily transpiration, net CO2 assimilation rate (A), stomatal conductance (gs), transpiration rate (E), chlorophyll a and b (chla, chlb), and the chla/chlb ratio, while increasing intrinsic water use efficiency (WUEi) across all rootstocks.
During recovery, M.793 and M.9 RN.29 trees exhibited rapid restoration of transpiration, while G.202, G.222, and M.7 recovered more slowly, suggesting potential adaptation responses.
In WD cycle 2, G.222 and M.9 RN.29 maintained higher A, maximum electron transport rate (Jmax), triose phosphate utilization (TPU), and maximum Rubisco carboxylation rate (Vcmax) compared to M.793, M.7, and G.202. Root biomass partitioning increased under WD for M.793 and G.222, but not for M.7, G.202, or M.9 RN.29. Trees on M.7, G.202, and M.9 RN.29 displayed a marked decrease in total dry mass accumulation in response to water deficit.
Results indicate that M.9 RN.29 is not more WD-sensitive than other rootstocks and can recover effectively.
These findings provide insights for rootstock selection and adapted irrigation scheduling to optimize water productivity under water-limited conditions.
Authors
L. Banda, S. Dzikiti, E. Lötze, S.J.E. Midgley
Keywords
apple rootstocks, biomass allocation, gas exchange, transpiration, water deficit, water use efficiency
Groups involved
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