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A rhizotron was used to study fine‐root demography in mature vines of kiwifruit (Actinidia deliciosa). The vines were grown in a deep, well drained, silt loam and received normal orchard management. Roots were measured from 10 to 160cm depth at biweekly intervals for 2 years. After an initial phase of rapid colonisation of the repacked soil behind the rhizotron windows, the total length of visible roots per vine remained quite steady. This apparent stability of the total belied fast and sustained localized turnover of the fine roots at all soil depths. Fifty‐one per cent of the roots survived ≤28d, 69% died at an age ≤56d and only 8% survived >252d. For each year, the cumulative length of roots grown was equivalent to about 2·75 times the maximum net length of roots visible. These may be the largest annual rates of root turnover yet reported. This has important ramifications for the carbon balance, mineral nutrition and water relations of the plant.

An internal blackening disorder may cause substantial losses in the value of tomatoes grown for processing. The disorder resembles an internal form of blossom-end rot and appears to be more common in dry seasons. In an experiment to test whether the internal blackening is caused by water deficit and whether it is indeed blossom-end rot, plots of cv. Cannery Row were irrigated to keep the soil moisture deficit c50 mm and others were sheltered from rain and not irrigated from early flowering onwards. Shoot growth (total and fruit dry mass) was measured destructively at intervals, and root growth and death nondestructively using minirhizotrons. There was a greater incidence of internal blackening and blossom-end rot, and lower Ca concentrations, in the fruit of non-irrigated plants. Root growth and root death were accelerated in these plants around the time that internally-blackened fruit were set. Although the internal blackening syndrome shared some features with blossom-end rot some differences were apparent in this experiment. It is suggested that internal blackening could have resulted from increased root competition for photosynthate, leading to abnormal seed development. Root turnover was appreciable (3040% of the roots survived < 28 days). This suggests there may be substantial errors in contemporary models of dry matter partitioning in tomato crops.

We investigated whether irrigation can affect the storage potential of kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson).Two experiments were carried out on mature kiwifruit vines growing in a deep silt loam near Gisborne, New Zealand. Experiment 1 (1990/91) mainly compared the effects of irrigation applied to replace different fractions of the shortfall between the weekly totals of potential evapotranspiration and rainfall. It also included a treatment in which early-season irrigation was withheld. Experiment 2 (1991/92) compared the effects of withholding irrigation at different times during the season. Fruit firmness was measured by penetrometer at intervals during storage. Withholding irrigation for the entire season improved fruit firmness during storage, but was accompanied by a significant depression in fruit size. Withholding irrigation until midsummer resulted in only mild water stress (fruit size was unaffected) but increased by c. 30 days the time H94046 taken for the firmness of stored fruit to decrease to 1 kgf or 0.2 MPa (the critical value for market acceptability). The mechanisms by which irrigation affected fruit storage properties are unclear.

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