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

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: The use of ultrasonic detectors for water stress determination in fruit trees. | 338s Ann. Sci. For. 1989 46 suppl. 338s-341s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA The use of ultrasonic detectors for water stress determination in fruit trees . Jones1 . Higgs2 and A. Bergamini3 11nstitute of Horticultural Research Wellesbourne Warwick . 2 Institute of Horticultural Research East Mailing Maidstone . and 3 Istituto Sperimentale per la Frutticoltura Trento Italy Introduction In drought the hydraulic conductance in tree stems can be reduced by embolisms that occur within xylem vessels and tracheids. There is good circumstantial evidence that these cavitation events can be detected acoustically either at low frequency . kHz Milburn and Johnson 1966 or high frequency . MHz Tyree and Dixon 1983 It is important to know at what stage cavitations occur and whether there are inherent differences between varieties or species. As a tool to investigate cavitation events we have used ultrasound detectors since they are able to operate in a noisy environment or in field conditions without background interference. Materials and Methods Using a circuit design based on that by Sandford and Grace 1984 acoustic emissions AE were converted into 5 V pulses and recorded on a counter or logger. AE production of 3 apple cultivars Cox s Orange Pippin Golden Delicious and A120 3 on 2 rootstocks and were compared in a glasshouse drought experiment from 8-10 October 1987. 24 potted trees were transferred from a sandbed on 4 October and water was withheld from 2 of each rootstock cultivar combination. Three days later water was withheld from one more tree from each combination the remainder of the trees being retained as well-watered controls. Two ultrasound transducers were attached to stems of pairs of trees to record counts over 5 min periods. Each transducer was mounted onto the xylem tissue of the rootstock stem covered with petroleum jelly about 10 cm below the graft union. Leaf water potential v down to -4 .

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