Physiological response of hopea odorata to water stress and soil compaction

Kamis A., . and Siti Rubiah Z., . (2003) Physiological response of hopea odorata to water stress and soil compaction. [Proceedings Paper]

Seedlings of Hopea odorata were grown in a series of soil columns compacted to bulk densities of 1.0 1.4 and 1.8 g cm- and subjected to two levels of watering. Reduction of photosynthesis and stomatal conductance of plants under high bulk density and water stress were relatively higher during the first 3 months compared to after 12 months of treatment due to the high soil strength that inhibit root penetration. However after 12 months higher values of photosynthesis and stomatal conductance were recorded probably due to the high root-shoot ratio which resulted in increased water absorption capacity of the root system. Physiological adaptations such as osmotic adjustment might have occurred causing an increase in the leaf water potential and the stomata to become less sensitive or to close as the drying progressed or a combination of both factors and the possible increase in xylem sap ABA concentration inducing the closure of stomata. The lower reduction in transpiration rate after 12 months of treatment indicated that more moisture was retained in H. odorata seedlings during drought. These physiological characteristics enabled H. odorata seedlings to maintain a certain degree of stomatal opening even towards the end of the experiment allowing for some photosynthesis to take place and hence preventing seedling starvation. The ability of H. odorata seedlings lo lose water at lower rates could help to explain their survival and greater competitive ability in some difficult sites in urban environment. In addition H. odorata seedlings could still maintain a positive carbon gain at a leaf water potential as low as -3.5 MPa.

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Abstract

Seedlings of Hopea odorata were grown in a series of soil columns compacted to bulk densities of 1.0 1.4 and 1.8 g cm- and subjected to two levels of watering. Reduction of photosynthesis and stomatal conductance of plants under high bulk density and water stress were relatively higher during the first 3 months compared to after 12 months of treatment due to the high soil strength that inhibit root penetration. However after 12 months higher values of photosynthesis and stomatal conductance were recorded probably due to the high root-shoot ratio which resulted in increased water absorption capacity of the root system. Physiological adaptations such as osmotic adjustment might have occurred causing an increase in the leaf water potential and the stomata to become less sensitive or to close as the drying progressed or a combination of both factors and the possible increase in xylem sap ABA concentration inducing the closure of stomata. The lower reduction in transpiration rate after 12 months of treatment indicated that more moisture was retained in H. odorata seedlings during drought. These physiological characteristics enabled H. odorata seedlings to maintain a certain degree of stomatal opening even towards the end of the experiment allowing for some photosynthesis to take place and hence preventing seedling starvation. The ability of H. odorata seedlings lo lose water at lower rates could help to explain their survival and greater competitive ability in some difficult sites in urban environment. In addition H. odorata seedlings could still maintain a positive carbon gain at a leaf water potential as low as -3.5 MPa.

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Item Type:	Proceedings Paper
Additional Information:	Available at Perpustakaan Sultan Abdul Samad Universiti Putra Malaysia 43400 UPM Serdang Selangor Malaysia. QK495 D564R859 2002 Call Number.
AGROVOC Term:	Hopea
AGROVOC Term:	Dipterocarpaceae
AGROVOC Term:	Forest trees
AGROVOC Term:	Tropical rain forests
AGROVOC Term:	Urban environment
AGROVOC Term:	Physiological response
AGROVOC Term:	Seedlings
AGROVOC Term:	Water stress
AGROVOC Term:	Soil compaction
AGROVOC Term:	Photosynthesis
Geographical Term:	MALAYSIA
Depositing User:	Ms. Suzila Mohamad Kasim
Last Modified:	24 Apr 2025 05:16
URI:	http://webagris.upm.edu.my/id/eprint/13404

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