Abstract
The overall aim of this study was to determine whether carbohydrate supply
from either photosynthesis or stored reserves limited inflorescence development in grape and kiwifruit vines in a similar way. Both grape and kiwifruit vines have a protracted period of inflorescence development, beginning with the initiation of floral meristems (all the processes needed to commit the meristem to produce an inflorescence) in spring of the first season, followed by a quiescent period before floral morphogenesis (development of four distinct whorls of floral organs - sepals, petals, carpels and stamens) occurs between budswell and anthesis in the second season. Patterns of growth, carbon acquisition and carbohydrate dynamics in Actinidia deliciosa ‘Hayward’ kiwifruit and Vitis vinifera ‘Shiraz’ and V. vinifera ‘Cabernet Sauvignon’ grapevines were generally consistent across vines and seasons. Overall, growth of vines could be divided into two key stages each season:
1. From budbreak to 100 days after budbreak (DAB) when the productive capacity of shoots was established. Mobilisation of carbohydrate reserves supported the initial stages of floral morphogenesis and shoot development (0 - 30 DAB). Thereafter, shoots became autotrophic but perennial reserves continued to decline until the end of the stage when maximum shoot leaf area and berry numbers were established.
2. From 100 - 250 DAB when shoot photosynthetic capacity supported berry development, root growth and carbohydrate accumulation in perennial tissues.
Inflorescence initiation occurred during rapid shoot growth in the first season of floral development but was not directly influenced by carbohydrate supply in either ‘Hayward’ or ‘Cabernet Sauvignon’ vines. Carbohydrate supply to shoots was modified during inflorescence initiation by phloem girdling (to prevent phloem transport) and either defoliation or shading (to reduce photosynthesis). Only girdling and defoliation of ‘Hayward’ shoots prevented inflorescence initiation, suggesting floral signals were leaf derived but not specifically carbohydrate. However, the growth of both ‘Hayward’ and ‘Cabernet Sauvignon’ shoots was also limited by carbohydrate supply during rapid shoot growth and this limited the capacity of shoots to store reserves in the autumn of that season.
Carbohydrate reserves stored in canes and roots in autumn of the first season of floral development were essential to support early floral morphogenesis in both ‘Hayward’ and ‘Cabernet Sauvignon’ vines during the spring of the second season of floral development. These reserves were manipulated by modifying photosynthesis and phloem transport during shoot growth in spring or vine carbohydrate accumulation in autumn of the first season of floral development. Reducing photosynthesis 5-fold in spring reduced shoot growth and was associated with a decrease of up to 35% in cane carbohydrate storage. In autumn, reducing photosynthesis decreased carbohydrate storage in canes (by 15%) and roots (by 40 - 50%), and cane girdling increased cane reserves (by 17%). Modifying cane reserves altered inflorescence production of ‘Hayward’ shshoots by up to 2-fold each season. Girdling ‘Cabernet Sauvignon’ canes increased inflorescence production of shoots by 30% in two seasons whereas, shading ‘Cabernet Sauvignon’ vines only reduced inflorescence production by 30% after three seasons, suggesting both root and cane reserves were important for this cultivar.
Reducing carbohydrate supply during late floral morphogenesis, particularly through lower photosynthetic rates of ‘Hayward’, ‘Shiraz’ and ‘Cabernet Sauvignon’ shoots decreased the number of flowers that reached anthesis (by 10 - 30%) and modified fruit set (by 60 - 130%), so that berry numbers were reduced by 10 - 30% at harvest. During this period of rapid shoot growth carbohydrate supply also determined the growth and photosynthetic capacity of shoots and hence their ability to support berry growth and reserve accumulation over the remainder of the season.
Therefore carbohydrate supply was essential for floral morphogenesis to proceed in both grape and kiwifruit vines, with the early stages dependent on carbohydrate from vine reserves and the later stages on carbohydrate from photosynthesis.
from either photosynthesis or stored reserves limited inflorescence development in grape and kiwifruit vines in a similar way. Both grape and kiwifruit vines have a protracted period of inflorescence development, beginning with the initiation of floral meristems (all the processes needed to commit the meristem to produce an inflorescence) in spring of the first season, followed by a quiescent period before floral morphogenesis (development of four distinct whorls of floral organs - sepals, petals, carpels and stamens) occurs between budswell and anthesis in the second season. Patterns of growth, carbon acquisition and carbohydrate dynamics in Actinidia deliciosa ‘Hayward’ kiwifruit and Vitis vinifera ‘Shiraz’ and V. vinifera ‘Cabernet Sauvignon’ grapevines were generally consistent across vines and seasons. Overall, growth of vines could be divided into two key stages each season:
1. From budbreak to 100 days after budbreak (DAB) when the productive capacity of shoots was established. Mobilisation of carbohydrate reserves supported the initial stages of floral morphogenesis and shoot development (0 - 30 DAB). Thereafter, shoots became autotrophic but perennial reserves continued to decline until the end of the stage when maximum shoot leaf area and berry numbers were established.
2. From 100 - 250 DAB when shoot photosynthetic capacity supported berry development, root growth and carbohydrate accumulation in perennial tissues.
Inflorescence initiation occurred during rapid shoot growth in the first season of floral development but was not directly influenced by carbohydrate supply in either ‘Hayward’ or ‘Cabernet Sauvignon’ vines. Carbohydrate supply to shoots was modified during inflorescence initiation by phloem girdling (to prevent phloem transport) and either defoliation or shading (to reduce photosynthesis). Only girdling and defoliation of ‘Hayward’ shoots prevented inflorescence initiation, suggesting floral signals were leaf derived but not specifically carbohydrate. However, the growth of both ‘Hayward’ and ‘Cabernet Sauvignon’ shoots was also limited by carbohydrate supply during rapid shoot growth and this limited the capacity of shoots to store reserves in the autumn of that season.
Carbohydrate reserves stored in canes and roots in autumn of the first season of floral development were essential to support early floral morphogenesis in both ‘Hayward’ and ‘Cabernet Sauvignon’ vines during the spring of the second season of floral development. These reserves were manipulated by modifying photosynthesis and phloem transport during shoot growth in spring or vine carbohydrate accumulation in autumn of the first season of floral development. Reducing photosynthesis 5-fold in spring reduced shoot growth and was associated with a decrease of up to 35% in cane carbohydrate storage. In autumn, reducing photosynthesis decreased carbohydrate storage in canes (by 15%) and roots (by 40 - 50%), and cane girdling increased cane reserves (by 17%). Modifying cane reserves altered inflorescence production of ‘Hayward’ shshoots by up to 2-fold each season. Girdling ‘Cabernet Sauvignon’ canes increased inflorescence production of shoots by 30% in two seasons whereas, shading ‘Cabernet Sauvignon’ vines only reduced inflorescence production by 30% after three seasons, suggesting both root and cane reserves were important for this cultivar.
Reducing carbohydrate supply during late floral morphogenesis, particularly through lower photosynthetic rates of ‘Hayward’, ‘Shiraz’ and ‘Cabernet Sauvignon’ shoots decreased the number of flowers that reached anthesis (by 10 - 30%) and modified fruit set (by 60 - 130%), so that berry numbers were reduced by 10 - 30% at harvest. During this period of rapid shoot growth carbohydrate supply also determined the growth and photosynthetic capacity of shoots and hence their ability to support berry growth and reserve accumulation over the remainder of the season.
Therefore carbohydrate supply was essential for floral morphogenesis to proceed in both grape and kiwifruit vines, with the early stages dependent on carbohydrate from vine reserves and the later stages on carbohydrate from photosynthesis.
| Original language | English |
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| Qualification | Doctor of Philosophy |
| Awarding Institution |
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| Supervisors/Advisors |
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| Award date | 31 Jul 2014 |
| Place of Publication | Australia |
| Publisher | |
| Publication status | Published - 2015 |