構樹苗木對光度之生理反應

Physiological Responses to Light Intensities of Broussonetia Papyrifera Seedlings

構樹廣泛分布於台灣中低海拔地區，其生育地之光環境變異極大。為了解其對不同光度的適應機制，本研究以不同光度處理其苗木，探討其形態及生理反應。試驗結果顯示，構樹苗木在低光下不但形態生長良好，且具有許多耐陰種之特徵，如比葉面積大（323.9cm2 g-1）、光補償點低（6.67μmol m-2 s-1）、葉綠素a／b比值小（2.46）等等，且在高光照射後有快速調適的保護能力。而生長在高光下的苗木則有良好的光合能力與消散機制，因此其對光度的適應範圍很廣，分布可從日射強烈之空曠地以至於鬱閉的防風林下。 Broussonetia papyrifera is an expansive distribution tree species from medium to lowelevation of Taiwan. The habitat of B. papyrifera has extreme differentiation in light environments.In order to understanding acclimation mechanism of B. papyrifera to different light intensity, we setvarious light treatment and observed the responses of phenotype and physiology. Results revealedthat, B. papyrifera had well performance in shade and shown several characteristics such as highspecific leaf area (323.9cm2 g-1), and low light compensation point (6.67 μmol m-2 s-1), chlorophyll a∕b ratio (2.46) of shade-tolerance species. B. papyrifera also shown the ability of fast recovery afterirradiated by high light. Therefore, B. papyrifera which grown in high light environment shown thewell photosynthetic capacity and mechanism of dissipation. So B. papyrifera acclimated broadly todifferent light environment and distributed from sunlit openness area to understory of windbreak forest.

Broussonetia papyrifera is an expansive distribution tree species from medium to lowelevation of Taiwan. The habitat of B. papyrifera has extreme differentiation in light environments.In order to understanding acclimation mechanism of B. papyrifera to different light intensity, we setvarious light treatment and observed the responses of phenotype and physiology. Results revealedthat, B. papyrifera had well performance in shade and shown several characteristics such as highspecific leaf area (323.9cm2 g-1), and low light compensation point (6.67 μmol m-2 s-1), chlorophyll a∕b ratio (2.46) of shade-tolerance species. B. papyrifera also shown the ability of fast recovery afterirradiated by high light. Therefore, B. papyrifera which grown in high light environment shown thewell photosynthetic capacity and mechanism of dissipation. So B. papyrifera acclimated broadly todifferent light environment and distributed from sunlit openness area to understory of windbreak forest.