Abstract
Alternate partial root-zone irrigation (APRI) can improve water use efficiency in arid areas. However, the effectiveness and outcomes of different frequencies of APRI on water uptake capacity and physiological water use have not been reported. A two-year field experiment was conducted with two irrigation amounts (400 and 500 mm) and three irrigation methods (conventional irrigation, APRI with high and low frequencies). Root length density, stomatal conductance, photosynthetic rate, transpiration rate, leaf water use efficiency, midday stem and leaf water potentials were measured. The results show that in comparison with conventional irrigation, APRI with high frequency significantly increased root length density and decreased water potentials and stomatal conductance. No differences in the above indicators between the two APRI frequencies were detected. A significantly positive relationship between stomatal conductance and root length density was found under APRI. Overall, alternate partial root-zone irrigation with high frequency has a great potential to promote root growth, expand water uptake capacity and reduce unproductive water loss in the arid apple production area.
Highlights
China has the largest apple production area in the world and accounts for 50% of global production capacity
Under conventional irrigation with large irrigation volumes and long irrigation intervals, there is a alternation of excess water supply and water deficit stress, which results in increasing stomatal conductance and luxury transpiration for a short time after irrigation, followed by reduced water potential and photosynthesis before the irrigation[3]
The objectives of this study were (1) to evaluate the impact of Alternate partial root-zone irrigation (APRI) with different irrigation frequencies on root length density, stomatal conductance, photosynthetic rate, transpiration rate, leaf water use efficiency, and midday stem and leaf water potentials in apple trees in arid north-west China, and (2) to analyze the relationship between stomatal conductance and root length density to understand the mechanism of efficient water use under this system
Summary
China has the largest apple production area in the world and accounts for 50% of global production capacity. Under conventional irrigation with large irrigation volumes and long irrigation intervals, there is a alternation of excess water supply and water deficit stress, which results in increasing stomatal conductance and luxury transpiration for a short time after irrigation, followed by reduced water potential and photosynthesis before the irrigation[3]. Previous studies indicated that promoting root growth, reducing luxury transpiration and regulating stomatal movement are important approaches to improve water use efficiency of fruit trees[4,5]. When water content of a tree is reduced, the decreased water potential and the increased tension of xylem result in the cavitation and embolization of xylem, which may reduce water transport capacity and decrease stomatal conductance[9]. The reduction of stem and leaf water potentials results in the decrease in leaf stomatal conductance under conventional irrigation[10,11,12]
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