The significance of changes in cytokinin content during early fruit growth was examined in the kiwifruit (Actinidia deliciosa var. deliciosa cv. Hayward). Fruit growth was modified by the reduction of seed number or by the application of the synthetic phenylurea cytokinin N‐(2‐chloro‐4‐pyridyl)‐N‐phenylurea (CPPU). The influence of these treatments on cell division was monitored by flow cytometry and changes in the endogenous cytokinins were measured at days 10 and 20 after anthesis, using high‐performance liquid chromatography and radioimmunoassay. Total cytokinin levels appeared not to be limiting growth since the highest total cytokinin concentration was detected in unpollinated fruit, which abscised by day 25 after anthesis. However, compared with control fruit which had the highest concentration of zeatin (Z) 10 days post anthesis, Z levels were low in unpollinated fruit. It is hypothesised that an increase in Z is the critical change in cytokinin metabolism required for the initiation of cell division and fruit growth. The synthetic cytokinin CPPU promoted fruit development, but there was a decrease in the endogenous cytokinin concentration. Zeatin was not detected in CPPU‐treated fruit. Cell division was reduced in unpollinated fruitlets but there was no significant difference (P > 0.05) between the other treatments. Differences in final fruit size appeared to be due to cell expansion.

The incidence and severity of soft rot, flower grades, and tuber yields of calla (Zantedeschia spp.) plants were affected by the quantity of water received during the growing season, sawdust mulch, and Enhance ® biocide applications to tubers before planting. Incidence of plants with soft rot symptoms increased at a relatively constant rate during the season reaching an average for all treatments of 61% at the end of flowering. Irrigated plus mulched callas had 15% less soft rot than the irrigation without mulch or the mulch without irrigation treatments. Yield of tubers was 90% greater from irrigated plants. Dipping tubers in Enhance ® before planting slightly reduced the severity of rotting in harvested tubers from non-irrigated plants. The total number of flowers was not affected by irrigation but was slightly reduced by sawdust mulch. However, the number of long stemmed flowers was increased 41% by irrigation, to over 1.5 per tuber.

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The effects of five nitrogen (N) application rates-14. 2, 28.4, 56.8, 113.6, and 227.2 g N/ m 2 (equivalent to 37.5, 75, 150, 300, and 600 ppm of N as a daily liquid feed), on greenhouse cut flower production and outdoor tuber production in Sandersonia aurantiaca (Hook.) were compared in two experiments using a peat:pumice medium. Stem length and weight declined with increasing N rate. Tuber weight declined slightly along with tuber quality with increasing N rate. High N rates resulted in an increased incidence of tuber disorders including secondary tuber formation and tuber rots. Leaf N concentration increased with N rate to a maximum of 56.8 g N/m 2 , but tuber N continued to increase (from 0.68 to 2.01% dry weight) with increasing N rate. The effects of the N rates on tuber storage and subsequent cut flower production were assessed at two N rates (28.4 and 113.6 g N/m 2 ) in a third experiment. Leaf nutrient concentrations were not affected when tubers were forced at the two N rates in the third experiment nor was vase-life of stems. This study indicates that sandersonia requires low-medium amounts of nitrogen and that an N rate of Received 12 May 1998; accepted I February 1999 c. 28.4 g/m 2 would optimise both tuber quality and stem production for sandersonia grown in a soil-less medium. Tuber and leaf nutrient concentrations at this N rate could be used for crop cultural guidelines for both flower and tuber production. H98021

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