Leaf area changes and transpiration in vineyards under salt stress

[摘要] ENGLISH SUMMARY: Irrigation of vines with saline water has long been a problem in the Western Caperegion. Research in this respect financed by the Water Research Commission was doneon vines to test the effect of 6 levels of irrigation water quality on production. Theexperiment consisted of two sites namely one at the Robertson experimental farm ofthe ARC outside of Robertson and the other on the Nietvoorbij experimental farmoutside Stellenbosch. Each site had 6 treatments replicated 4 times. The treatmentsconsisted of water with electrical conductivities of -40, 75, 150, 250, 350, 500 mS/m.The saline water was produced and controlled by a computerised injection system thatinjected a high concentration stock solution into the irrigation system. The stocksolution consisted ofNaCI and CaCl2 mixed to a Na:Ca ratio.Description of the canopy surface and structure per plant is essential to the formulationand description of plant reaction resulting from plant-environmental interaction. Thisstudy looked at measurement techniques to non-destructively describe and quantify thereaction of canopies to different saline treatments. Measurement techniques consistedof physical destructive and non-destructive light interception techniques with specialreference to the use of the Sunfleck Ceptometer and Dcor C2000 Plant CanopyAnalyser. Destructive measurements were only done to calibrate the non-destructivetechniques. The Dynamax Heat Balance Sap Flow Meter was used to measuredifferences in sap flow rate between plants from different treatments. The measuredtranspiration was compared with weather station derived evapotranspiration as well asthe sodium absorption ratio of the different soils.It was found that leaf area indices do show treatment effects very clearly. It was alsofound that by the time treatment effects were visible, leaf damage was alreadyirreversible. The method clearly highlights treatment effects but cannot be used in aproduction environment to help prevent leaf damage as a management tool. Sap flowmeasurement was done to show that sap flow is more sensitive and that differences dooccur before leaf damage is visible. Sap flow measurements can therefore be used withgreater success as a management and a research tool. A good calibration exercise todetermine leaf area indices non-destructively led to the ability of producing reliabletranspiration and evapotranspiration data.

[发布机构] Stellenbosch University