Effects of root restriction on growth, flowering and water uptake of starfruit

M. Zainudin

Abstract

Starfruit plants cv. B17 were subjected to four different container sizes namely 3, 6, 12 and 24 litres to determine the effects of root restriction on growth, flowering and water uptake. The experiment was carried out using randomised complete block design with three replications. Each experimental unit consisted of three plants. At the sixth month, a sensor was installed into the plant stem of each treatment for three consecutive weeks to measure the sap flow. The entire experiment was carried out under a glasshouse for eight months. Irrigation and fertilization were given accordingly to schedule. The growth was linearly increased with container volumes suggesting that plant growth was retarded under root restricted conditions. Similar trend response was observed in dry matter percentage distribution. However, root dry matter percentage (DRMP) did not follow the same manner whereby DRMP increased by 38% in 3- or 6-litre compared to 26.5% in 24-litre containers. The ‘day to flowering’ was 60 days earlier with respect to decrease in similar container volume. But, sap flow velocity reduced from 22.3 to 9.5 cm/h and leaf water potential increased from –1.2 to 2.2 MPa when container volume reduced by eight folds. The physiological changes of the plant were due to the root restriction resulting from different container sizes.

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