Articles
MODELLING THE WATER TRANSPORT DYNAMICS IN YOUNG NAVEL ORANGE TREES BUDDED ON ROOTSTOCKS COMMONLY GROWN IN NORTHERN ZIMBABWE
Article number
803_33
Pages
259 – 264
Language
English
Abstract
Interpretation of the water relations of most citrus cultivars is difficult due to the occurrence of stomatal oscillations whose origin is not well known.
These oscillations present sampling problems in water resource management in citrus orchards using discrete measurements of plant-based stress indicators.
In this study we investigated the effect of two rootstocks commonly grown in northern Zimbabwe on the characteristics of the oscillations in Navel orange trees.
This information was useful in deciding the optimal sampling frequency needed to obtain representative estimates of the plant water status.
In addition, insights on the possible origin of the oscillations were also gained.
The rootstocks comprised the rough lemon which is efficient in water uptake and produces drought tolerant trees and the troyer citrange which is less efficient in water uptake but it produces high quality fruit.
Oscillations in sap flow, stem diameter and leaf water potential had sustained amplitudes and longer periods (>70 min) for orange trees budded on the troyer citrange rootstock, while trees on the rough lemon rootstock produced faster oscillations with diminishing amplitudes and short periods ranging from 35 to 55 min.
A simple water balance model was used to describe the water relations of the trees budded on these two rootstocks.
In this model, transpiration by the crown was used as the driving variable for stem sap flow, while the plant resistance (Rx) and capacitance (C) were parameter values obtained by model calibration.
No significant differences in the estimates of Rx were found between the rootstocks, although this resistance appeared to change throughout the day.
It is probable that the fluctuating resistance played a part in generating the stomatal oscillations through changes in the efficiency of water transport, which created transient internal water deficits in the leaves.
These oscillations present sampling problems in water resource management in citrus orchards using discrete measurements of plant-based stress indicators.
In this study we investigated the effect of two rootstocks commonly grown in northern Zimbabwe on the characteristics of the oscillations in Navel orange trees.
This information was useful in deciding the optimal sampling frequency needed to obtain representative estimates of the plant water status.
In addition, insights on the possible origin of the oscillations were also gained.
The rootstocks comprised the rough lemon which is efficient in water uptake and produces drought tolerant trees and the troyer citrange which is less efficient in water uptake but it produces high quality fruit.
Oscillations in sap flow, stem diameter and leaf water potential had sustained amplitudes and longer periods (>70 min) for orange trees budded on the troyer citrange rootstock, while trees on the rough lemon rootstock produced faster oscillations with diminishing amplitudes and short periods ranging from 35 to 55 min.
A simple water balance model was used to describe the water relations of the trees budded on these two rootstocks.
In this model, transpiration by the crown was used as the driving variable for stem sap flow, while the plant resistance (Rx) and capacitance (C) were parameter values obtained by model calibration.
No significant differences in the estimates of Rx were found between the rootstocks, although this resistance appeared to change throughout the day.
It is probable that the fluctuating resistance played a part in generating the stomatal oscillations through changes in the efficiency of water transport, which created transient internal water deficits in the leaves.
Authors
S. Dzikiti, J.R. Milford, K. Steppe, R. Lemeur
Keywords
dynamic model, leaf water status, plant resistance, sap flow, stomatal oscillations
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