Semi-mechanistic model for oxygen consumption by fruit-tree roots varied by changes in environmental conditions
1999
Kumut Sangkhasila (Kasetsart Univ., Bangkok (Thailand). Faculty of Agriculture. Department of Soil Science)
Measurement of oxygen comsumption by roots has been conducted from two mango seedlings. These two seedlings were grown separately in closed chambers. Only a root part of each seedling was grown in a closed chamber while its shoot part can directly contact with the diurnal changes in climatic conditions. The rate of oxygen consumption was measured in accordance with climatic and physiological parameters. These parameters are measured on the diurnal basis. The results of climatic measurement suggested that these two seedlings were grown under a normal condition for a rainy season. Air temperatures varied from 24 to 25.5C diurnally. Relative humidity was quite high for the whole period of the measurement, i.e. it was higher than 80 percent. The photosynthetically photon flux density started to be available at 6:00 and vanished at 18:30 with its peak of 2040 mu mol 1/square m/s at 11:50. Soil temperatures for both chambers were normally varied following the diurnal change in air temperature. Soil water content was high for the whole period of measurement suggesting that it would not induce the water stress condition for the two seedlings. Seedlings no.1 had a 107.0 square cm leaf-area. All of its leaves are young and active. The rate of transpiration for this seedling was 680.0 mm d/square m -leaf area while its rate of oxygen consumption by its roots was 113.11 mg/d square m -leaf area. Seedling no.2 had a 590.5 square cm leaf area. All of its leaves were mature. Its rate of trapiration was 71.6 mm/d square m -leaf area while its rate of oxygen consumption by roots was 30.64 mg/d square m -leaf area. More measurements are in the need for a construction of an oxygen consumption by roots model.
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