Pramlintide in combination with insulin is a potential therapeutic option for improving glycemic control in patients with diabetes, but the increased risk of hypoglycemia must be aggressively monitored.

This paper presents patterns of change in non-structural carbohydrate concentrations of 1-year-old shoots over a 2-year period for 'Braeburn' apple trees (Malus domestica) growing in the Waikato region of New Zealand. Carbohydrates analysed by enzymatic analysis included starch, sorbitol, sucrose, glucose, and fructose. Sorbitol concentrations were found to be higher than starch for most periods of the year and sorbitol comprised the majority of the total carbohydrates. Starch concentrations were never completely depleted, even during periods of rapid growth. These patterns of carbohydrate change were similar to those reported from Northern Hemisphere studies for a variety of deciduous fruit tree species, indicating that carbohydrate changes in New Zealand trees are comparable with trees worldwide, despite the long period of leaf retention after harvest in New Zealand.

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This work investigates the pathway and mechanism for lateral retrieval of carbohydrate into the transport phloem of apple stems (Malus domestica Borkh.). A heat exchanger was set up on the stem, allowing rapid chilling and subsequent re-warming of stem segments while the time course of axial transport of 11C-labelled photoassimilate was measured at a position ∼65 mm downstream of the heat exchanger. Whenever axial transport was blocked by a sudden chill at the heat exchanger, transport 65 mm downstream from the blockage immediately slowed but did not stop, showing that there was retrieval of solutes into the pathway (buffering), within that 65 mm of stem, to help maintain the axial flow. Use of PCMBS, an inhibitor of sugar transporters, showed that the buffering included retrieval of sugar from the apoplast. We concluded that in apple, apoplastic sugar in stem tissue can buffer phloem transport during short-term changes in supply and demand for carbohydrates. Buffering was stronger when mobile reserves in the stem were higher, for example late in the photoperiod, or if carbohydrate demand in the terminal sink was increased. We also suggest that the concentration of sugars in the apoplast is a regulator of carbohydrate storage and re-mobilisation.

No abstract