Michael Clearwater

ABSTRACT The aim of this work was to investigate the roles of the apoplasmic and symplasmic pathways in the delivery of solutes to the outer pericarp of developing green-fleshed kiwifruit berries (Actinidia deliciosa [A. Chev.] C. F. Liang et A. R. Ferguson var. deliciosa Hayward'). Experiments with the symplasmic tracer 5(6)-carboxyfluorescein (CF) showed symplasmic movement of dye during the initial rapid growth stage of the fruit, but as fruit growth slowed and starch content increased, a reduction in symplasmic spread of CF was observed (+126 DAA [days after anthesis]). Measurements of sugar uptake rates from the apoplasm were sufficient to account for the dry matter accumulation in growing fruit at each stage of fruit growth, and could potentially operate alongside a symplasmic pathway for post-phloem unloading of sugars during the rapid growth period. Energy requirements driving uptake from the apoplasm appear to depend on the sugar concentration gradients across the cell membrane throughout fruit development. Together, these data suggest: 1) the post-phloem symplasmic pathway is important during the fruit rapid growth stage, 2) the uptake of sugars from the apoplasm has a role in the transport of carbohydrates in the fruit, especially later in fruit development when the symplasmic pathway is reduced, and 3) apoplasmic sugar has an important role in the flow of water into the apoplasm of the fruit, providing a mechanism to maintain hydrostatic pressure gradients along the phloem supplying the fruit.

ABSTRACT The distribution of the endemic kauri (Agathis australis) coincides with one of the regions of New Zealand which will suffer more frequent and severe summer droughts under future climates. However, very little is known about the water-relations of this slow-growing and iconic species. We measured sap flux density (Fd) in mature kauri trees across an 18-month period. Here we present an exploration of the variation in Fd at different sapwood depths. Quantifying radial variation in Fd is important for estimation of whole-tree water use of trees with considerable sapwood depth. Sapwood depth of kauri trees was up to 18 cm and there was significant variation in the rate of water movement across the radial profile. We centred 1 cm probes at 1, 3, 5, 7 and 9 cm depths and found the greatest Fd occurred at the 2.5-3.5 interval. Peak Fd at other depths was between 20 and 60% of the 3 cm peak. This pattern was consistent across seasons. We also compared Fd across contrasting field conditions. We chose three rain free periods of ten days in length during January 2012 (wet summer), July 2012 (wet winter) and January 2013 (dry summer). Sap flux density was largest during the wet summer period and smallest during the dry summer period. Regression analysis showed a stronger relationship between vapour pressure deficit (D) and Fd during the dry summer while the slope of the relationship was steeper during the wet summer, indicating stomatal regulation of Fd. In addition, nocturnal sap flow indicated stem water storage is another potential drought avoidance mechanism used by kauri.

A method was designed and validated for the analysis of dihydroxyacetone in the floral nectar of ma̅nuka (Leptospermum scoparium). The method was applied to samples collected from different regions of the North Island and the Nelson region of the upper South Island of New Zealand during the period 2009-2012 as well as to nectar samples from some Australian Leptospermum species. The ratio of dihydroxyacetone to total sugar (DHA/Tsugar) was classified as low (<0.001 mg/mg), moderate (0.001-0.002 mg/mg), or high (>0.002 mg/mg). Inter- and intraregional variation were observed as well as interannual variation with variation from low to high classification occurring within one region and from low to moderate between years. Australian species also demonstrated elevated levels of dihydroxyacetone in the nectar. Some garden cultivars were shown to produce very high nectar DHA/Tsugar, and a survey of cultivars was undertaken; cultivars with single-flowered red or pink flowers were the ...

Information on the biology and ecology of Griselinia lucida (Forst. f.) (Griseliniaceae) available through published and unpublished sources is assembled and reviewed. G. lucida is a large shrub hemiepiphyte that grows primarily in trees of wet, lowland forests and also in open coastal and rocky outcrop habitats. Large, bright green, glossy leaves and grooved terrestrial roots that descend from the