Effects of a pre-flower phloem girdle on root pressure and partitioning of carbohydrate in Actinidia chinensis var. deliciosa 'Hayward'
Haisman, N. A. (2019). Effects of a pre-flower phloem girdle on root pressure and partitioning of carbohydrate in Actinidia chinensis var. deliciosa ‘Hayward’ (Thesis, Master of Science (MSc)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/12552
Permanent Research Commons link: https://hdl.handle.net/10289/12552
The objective of this research is to understand the impacts of applying a pre-flower trunk girdle to the kiwifruit cultivar ‘Hayward’ (Actinidia chinensis var. deliciosa). The pre-flower girdle is a recent addition to the management of ‘Hayward’ kiwifruit orchards since it was discovered that it can reduce flower budrot. However, the effects of a trunk girdle in early spring on the partitioning of resources through the vine and the impacts on vine growth are unknown. Two approaches were used to address the objective. The first approach was to use mature ‘Hayward’ vines at the Plant and Food Research Orchard, Te Puke in the Bay of Plenty. The aims were to determine if xylem mobile sugars are important in the development of spring root pressure, and to define the impacts of a pre-flower girdle on root pressure, carbohydrate partitioning and storage, and vine phenology within the vine. The second section of research used the detection of Bremmstrahlung radiation to trace the in vivo movement of radiolabelled photosynthate through ‘Hayward’ scions recently grafted onto Bruno rootstocks. The aim was to understand how stem girdling effects the movement of carbohydrate between source and sink tissues of young developing vines. Key results of this research were that the refilling of xylem vessels and the establishment of hydrostatic pressure in early spring occurs gradually from the roots up the trunk of the vine. Fructose in the fine roots was identified as a key carbohydrate in the generation of the hydrostatic pressure required to refill xylem conduits after winter dormancy. After a pre-flower trunk phloem girdle was applied there was a loss of xylem pressure that lasted for two weeks. The cause has not been resolved though results from this study suggest a relationship with loss of phloem flow, or cavitation induced air embolisms in the xylem preventing xylem pressure recovery. Leaves from girdled vines exported less carbohydrate than non-girdled vines which suggests a delayed transition to an autotrophic status. Root and trunk carbohydrates showed little short-term effect of the pre-flower girdle. However, there was a location effect seen with the trunk bark carbohydrates that suggest the utilisation of ‘local’ reserves is exploited in preference to long-distant transport of reserves. There was no detectable short-term impacts of the pre-flower girdle on phenology. Further research is proposed to understand the long-term impacts of a pre-flower girdle on root pressure, carbohydrate storage and the development of seasonal organs.
The University of Waikato
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