Root and xylem ABA changes in response to soil drying in two woody plants |
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Authors: | Huafang Wang Jianhua Zhang Jiansheng Liang Weilun Yin |
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Institution: | (1) College of Plant Science, Beijing Forestry University, 100083 Beijing, China;(2) Department of Biology, Hong Kong Baptist Uniwrsit, Hong Kong, China |
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Abstract: | Two woody plants,Platycladus orientalise (tolerant to drought) andAcacia auriculiformis (sensitive to drought), have been subjected to rapid and slow soil drying. ABA levels in their roots and xylem sap have been
determined using radioimmunoassay (RIA, sensitivity is 0.4 pmol per assay vial) with a monoclonal antibody against ( + )-ABA.
ABA contents ofP. orientalise andA. auriculiformis growing in well watered soil are 0.3 and 2.5 nmol · g
ow
−1
in roots and 1.6 and 0.4 μmol in xylem saps, respectively. A rapid soil drying has been applied to these two plants with
soil water content (SWC) being reduced to 0.02 and 0.06 g · g
ow
−1
respectively. Under such treatment, ABA was increased by 22 times and 2 times in roots and by 7 times and 34 times in xylem
saps respectively forP. orientalise andA. auriculiformis. After rewatering for 6 d, ABA in roots and xylem sap of both species returned to control levels. When a slow soil drying
was applied, SWC was reduced to 0.1 and 0.13 g · g
OW
−1
respectively forP. orientalise andA. auriculiformis. ABA was increased by 5 times and 1.6 times in roots and by 6 times and 19 times in xylem saps respectively for these two
plants. ABA in roots and xylem saps decreased to near control levels 8 d after watering. Plant leaf water potentials of both
plants hardly changed at times when root and xylem ABA showed substantial increase in response to soil drying. It is concluded
that ABA levels in the roots and xylem saps ofP. orientalise andA. auriculiformis are more sensitively regulated than leaf water potential in response to soil drying and can act as a chemical signal in root-shoot
communications of the drought stress. |
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Keywords: | Platycladus orientalise Acacia auriculiformis root xylem sap ABA soil drying |
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