No abstract

Components of the carbon balance in the Sultana vine (Vitis vinifera L.) were examined with emphasis on the autumn, post-harvest, period. The net photosynthetic rate (PN) of leaves decreased from 0.30 to 0.03 mg CO2 m-2 s-1 from January to May (late summer to autumn). Two-thirds of this decline cocurred in the month before leaf fall. This decline in PN as senescence progressed was mainly due to increases in the 'residual', non-gas-phase, resistance to CO2 transfer. 14C-labelled assimilates were shown to move from the leaves to the perennial portions of the vine in both early and late autumn, and this 14C label reappeared in the shoot growth of the following spring. However, the level of carbohydrate reserves in shoots, roots or trunk in the autumn to spring period was not significantly affected by a severe (c. 60%) defoliation in early autumn. This level of defoliation, which the vine is able to tolerate without cumulative effects, occurs where Sultana vines are 'harvest-pruned' as part of the harvesting method of trellis drying.

An experiment IS dcsci bed which lasted for SIX seasons and was designed to investigate the response of the cultivar Qouchen (syn Clare Riesling) to various trellising and pruning treatments This cultivar, which achieves high levels of bud fruitfulness when grown In the Murray Valley, responded to widening the trellis from 0.3 m to 1.4 m with an increase In yield of 25–30%. This yield Increase was largely due to a better bud burst for vines on the wider trellis. Increasing the number of nodes per vine from 32 to 48 caused a yield Increase of about 15 %, but a further Increase to 64 nodes d i d not result in any additional yield response In the initial year of the trial, spur- and cane-pruned vines (with node numbers in the ratio of 4 to 5) yielded equally well. But In later years spur-pruned vines gave increasingly better yields, again resulting from differences In bud burst. To investigate the relationship between wine quality and yield, the fruit of four combinations of pruning and trellising treatments, giving a range of yields, was made into wine. Small-scale wine-making techniques were used No significant differences In wine quality attributable to the yield differences were found.

Vegetative and reproductive growth was recorded on mature mango trees (cultivar Kensington) over two years in northern Australia. There were four vegetative growth flushes during each year, but not all shoots grew during each flush. Observations on the flowering of shoots of known age showed that the older shoots produced most inflorescences. Microscopic examination of terminal buds showed that floral initiation occurred within a month of the commencement of the flowering flush under these tropical conditions. The main vegetative growth flushes occurred prior to flowering between March and May, and during flowering and early fruit development in July and August.

Avocado trees of a range of cultivars growing in Darwin, northern Australia (average yearly maximum 33°C, minimum 23°C), were observed for flower and shoot development. Terminal buds of the cultivars 'Fuerte', 'Rincon' and 'Edranol' sampled in July were not floral. Buds which did not burst were sampled in September and they contained developing flowers with perianth primordia. Vegetative extension growth resulted from laterals proximal to the inhibited terminal buds.Avocado trees of the cultivars 'Fuerte' and 'Hass' which had initiated floral buds were transferred to controlled environment chambers with 33°C day, 23°C night (33]23) or 25°C day, 15°C night (25/15) with a 12-h photoperiod and photon flux density of 400 umol m -2 s -1 (400--700 nm). At 33/23 the trees had fewer flowers and a shorter flowering period than at 25115. Inhibited floral buds and lateral vegetative extension resulted at 33•23, as observed in northern Australia. The unburst buds had developing flowers with perianth and stamen primordia.The controlled environment experiments showed that the abnormal flushing behaviour of Mexican-and Guatemalan-type avocados growing in northern Australia was due to high temperature. Floral development was inhibited at the stage of stamen differentiation.