Plant water relation, 식물생리학 report

소개글

plant water relation에 대해 실험한 것으로 water potential과 osmotic pressure에 대해 정리해 놓았습니다~! 그리고 osmotic pressure 측정하는 방법에 대해 정리해 놓았습니다

목차

Plant water relation
Measurement of Osmotic Potential

ABSTRACT: 실험과정의 요약
INTRODUCTION : 이번 실험에서 한 plant water relation, water potential, osmotic pressure 에 대해 구체적인 설명. 그리고 water potential의 식 유도 방법.
MATERIALS & SUPPLIES : 실험에서 사용한 각종 기구 및 시약
PROCEDURE : 실험 과정
RESULT : 실험 결과를 그래프로 그려 나타냄
DISCUSSION : 이번 실험에 대한 고찰 및 water potential에 대한 법칙과 다른 방법을 통한 water potential 측정방법.
CONCLUSION : 실험 결론에 대한 간단한 언급
REFERENCE : report 작성을 위해 참조한 각종 논문 및 책, 그리고 인터넷 사이트 공개

본문내용

INTRODUCTION

Without water, life as we know it could not exist. Water is the most abundant constituent of most organisms. The actual water content will vary according to tissue and cell type and it is dependent to some extent on environmental and physiological conditions, but water typically accounts for more than 70 percent by weight of nonwoody plant parts. The water content of plants is in a continual state of flux, depending on the level of metabolic activity, the water status of the surrounding air and soil, and a host of other factors. Although certain desiccation-tolerant plants may experience water contents as little as 5 percent water, both are metabolically inactive and resumption of significant metabolic activity is possible only after the water content has been restored to normal levels(7).
The entry of water into plant tissue is essential for cell enlargement. This flow of water through plants is a matter of considerable significance to their growth and survival. The uptake of water by cells generates a pressure known as turgor; in the absence of any skeletal system, plants must maintain cell turgor in order to remain erect. Since water absorption occurs along gradients of decreasing water potential, the water potential of growing plant tissue must be below that of the water supply(1). The steepness of the gradient should depend on the resistance of the tissue to water flow(4).

Movement of substances from on region to another is commonly referred to as translocation. Mechanisms for translocation may be classified as either active or passive, depending on whether metabolic energy is expended in the process. The metabolic translocation of water is clearly a passive process. Passive movement of most substances can be accounted for by one of two physical processes: either bulk flow(or mass flow) or diffusion. In the case of water, a special case of diffusion known as osmosis must also be taken into account.
Movement of materials by bulk flow is pressure-driven. Bulk flow occurs when an external force, such as gravity or pressure, is applied. As a result all of the molecules of the substance move in a mass.
Diffusion can be interpreted as a directed movement from a region of a high concentration to a region of lower concentration, but it is accomplished through the random thermal motion of individual molecules.
Diffusion of water, a process known as osmosis, will occur only when the tow chambers are separated from on another by a selectively permeable membrane. Recall that a selectively permeable membrane allows virtually free passage of water and certain small molecules, but restricts the movement of large solute molecules, and that all cellular membranes are selectively permeable. Osmosis is simply a special case of diffusion through a selectively permeable membrane.
Water, like any other substance, will only move down an energy gradient-
that is, when there is a difference in the energy of water in two parts of a system.
The energy content of water, like any substance, is most easily described in terms of its chemical potential. Chemical potential(μ) is defined as the free energy per mole of that substance. The rule is that osmosis occurs only when there is a difference in the chemical potential of water on two sides of a selectively permeable membrane.
Osmosis can be easily demonstrated using a device known as an osmometer, constructed by closing off the open end of a thistle tube with a selectively permeable membrane [fig1]....

참고 자료

1. Brouwer, R. The influence of the nutrient solutions on growth, transpira-
tion and diffusion pressure deficit of bean leaves (Phascolus zulglaris). Acta Bot. Neerl. 1963; 12:248-61.
2.http://4e.plantphys.net/article.php?ch=3&id=29
3. J. B. Dandeno. Osmotic Theories, with Special Reference to Van`t Hoff`s Law. Bulletin of the Torrey Botanical Club, 1909; Vol. 36, No. 6
4. John s. Boyer. Relationship of Water Potential to Growth of Leaves. Plant Physiol. 1968; 43(7):1056-1062.
5. John H. Northrop. The Kinetics of osmosis. The Journal of General Physiology, 1927; Vol 10, 883-892
6. Michael J. Savage and Alfred Cass. Psychrometric Field Measurement of Water Potential Changes following Leaf Excision. Plant Physiol. 1984 January; 74(1): 96–98.
7. William G. Hopkins&Norman P. A. Huner. Plant Cells and Water. In: Introduction to Plant Physiology 3th Edition. John Wiley&Sons, Inc. 2004; p 201-213