Báo cáo lâm nghiệp: The use of ultrasonic detectors for water stress determination in fruit trees

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Báo cáo lâm nghiệp: " The use of ultrasonic detectors for water stress determination in fruit trees"The use of ultrasonic detectors for water stressdetermination in fruit trees 2 Higgs 3 Bergamini A. K.H.H.G.Jones1 Institute of Horticultural RResearch, Wellesbourne, Warwick, U.K., tural esearch, W .K., urne,2 Institute of Horticultural Research, East Malling, Maidstone, U.K., and3 Istituto Sperimentale per la Frutticoltura, Trento, Italy converted into 5 V pulses and recorded onIntroduction were logger. AE production of 3 apple a counter or cultivars (Cox’s Orange Pippin, Golden Deli- cious and /t?20/3) on 2 rootstocks (M.9 and conductance inIn drought, the hydraulic M.25) were compared in a glasshouse droughttree stems can be reduced by embolisms experiment from 8-10 October 1987. 24 pottedthat occur within xylem vessels and tra- trees were transferred from a sandbed on 4cheids. There is good circumstantial evi- October and waiter was withheld from 2 of each rootstock/cultivar combination. Three days later,dence that these cavitation events can be water was withheld from one more tree fromdetected acoustically, either at low fre- each combination, the remainder of the treesquency, i.e., 0.2-2 kHz (Milburn and John- being retained as well-watered controls. Twoson, 1966) or high frequency, i.e., 0.1-1.0 ultrasound transducers were attached to stems of pairs of trees to record counts over 5 minMHz (Tyree and Dixon, 1983) It is impor- periods. Each transducer was mounted onto thetant to know at what stage cavitations xylem tissue of the rootstock stem (coveredoccur and whether there are inherent dif- with petroleum jelly) about 10 cm below theferences between varieties or species. As graft union. Leaf water potential ( down to -4 , VIa tool to investigate cavitation events, we MPa) and conductance to water vapor (g were ) i monitored concurrently with AE.have used ultrasound detectors, sincethey are able to operate in a noisy envi-ronment or in field conditions withoutbackground interference. Results Results presented for the 3 cultivars areMaterials and Methods in Fig. 1. There was a clear separately rootstock effect with the count rate for M.9 being up to Ei times that for M.25, de- design based on that by Sand-Using a circuit pending upon y. The threshold of y!i atford and Grace (1984), acoustic emissions (AE) a data logger recording at 30 min using intervals. Two ’ were used: A120/3 on trees M.25 and Cox on M.9. The pattern of V, vs AE was similar to that i ...