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가속기 X선 영상기법을 이용한 애기장대 뿌리털의 물 흡수과정 가시화
황배근(Bae Geun Hwang),김혜구(Hae Koo Kim),이상준(Sang Joon Lee) 한국가시화정보학회 2010 한국가시화정보학회지 Vol.8 No.4
Water-uptake through roots, is an essential process of the water flow in plants. Its visualization is very useful for understanding sap flow dynamics at whole plant level. In this study, the tips of Arabidopsis' root hairs were excised and exposed to repeated dehydration and rehydration processes. The water-refilling through individual xylem vessels was visualized using the synchrotron X-ray micro-imaging technique. The high temporal resolution (2 ㎛) and beam intensity of the X-ray source allowed to acquisition of consecutive X-ray images of the water-refilling process up to 10 frames/sec. Various flow patterns were observed and the ascending speed of the water-air interfaces was analyzed. The relation between the water-rising height and ascending speed was also analyzed. The present results would provide better alternative for investigating sap flows in roots.
가속기 X 선 영상기법을 이용한 Arabidopsis 뿌리털의 물 흡수과정 가시화
황배근(Bae Geun Hwang),김혜구(Hae Koo Kim),이상준(Sang Joon Lee) 한국가시화정보학회 2010 한국가시화정보학회 학술발표대회 논문집 Vol.2010 No.11
Water uptake through roots, is an essential function of the water circulation of plants, and it is indispensable for understanding the whole sap flow dynamics. In this study, the tips of Arabidopsis’ root hairs were excised and exposed to dehydration and rehydration cycles. During this process, the water-refilling process inside the xylem vessels of root hairs was visualized using the synchrotron X-ray imaging technique which has a high spatial resolution of 2 ㎛. High temporal resolution and sufficient beam intensity of the X-ray source make it possible to record consecutive images of the water-refilling process up to 10 frames/sec. Various flow patterns were observed and the ascending speed of the water-air interfaces was analyzed. The relations between the upward-rising height and ascending speed were also analyzed. The present results would be helpful for understanding sap flows in roots.
X-ray imaging of sap flow and embolism in xylem vessels of rice leaf
김혜구(Hae Koo Kim),황배근(Bae Geun Hwang),이상준(Sang Joon Lee) 한국가시화정보학회 2009 한국가시화정보학회 학술발표대회 논문집 Vol.2009 No.11
The transport system that drives sap ascent from soil to leaves in a plant is extraordinary but the underlying mechanisms still not completely understood. In vascular plants, the xylem is responsible for the transport of water and nutrients. According to the most widely accepted view by plant physiologists, the cohesion-tension (CT) theory states that the pressure difference between root and leaves is the driving force of the water transport in xylem, generated by surface tension at the evaporating surfaces of the leaf. The negative pressure is transmitted through the continuous water column in the rigid xylem vessels to all parts of the plant. Although the CT theory has been around for more than a century, lack of proper measurement techniques did not allow to test the validity in living intact plants. The methodologies to investigate the forces and processes responsible for xylem transport are increasing rapidly but appropriate techniques to quantify and visualize sap flow dynamics in intact plants are limited. Heat-based methods and radioisotope labelling techniques have been used to estimate flow velocities and mass flows. In recent years, magnetic resonance imaging (MRI) is most commonly used as a non destructive method for measuring the dynamics of the water content in xylem vessels. In this study, X-ray micro-imaging methodology is used to investigate in vivo the sap flow dynamics in relation to the structure of xylem vessels and unravel their function in plant hydraulics. Water refilling and embolism apparition processes were monitored at the level of an individual xylem vessel with a high spatial (1 μm) and temporal (0.03s) resolution in rice leaf blade and sheath. The sap flow velocity variations during refilling and dehydration cycles were directly related with the presence of pit membranes at the end of xylem vessels. The direct visualization of pit membranes during those processes emphasized its central role in hydraulic resistance and embolism mechanisms.