SOIL 620

SPRING 1997

FINAL REPORT

PRESSURE BOMB

BY:

Mario Valenzuela-Vazquez

Artemio Escobedo-Mendoza

Jose Luis Almanza-Sandoval

Asunción Ríos-Torres


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Introduction

Plant growth occurs when water balance within plants is favorable or in period of high plant water potential. Water potential acting directly or indirectly is a determinant of all plant functions, such as cell expansion, photosynthetic rate (stomatal conductance, dark and light reactions), respiration, biosynthesis, etc.

In an attempt to understand and measure the water function in plant tissues, several devices have been developed. The pressure bomb, also known as a plant water status console, is a useful instrument when doing research in plant water relationships. In addition, when data obtained with this device is properly correlated to soil water potential and potential evapotranspiration data, it is a useful tool for irrigation scheduling.

The pressure bomb determines the balance pressure of a cut plant's tissue. Such balance in pressure seems to be equivalent to the xylem pressure potential before the plant was cut. Other complementary issues of plant water status can be measured such as fuel turgor potential, symplastic water and bound water. There are several models of water status consoles, such as those constructed by Soilmoisture Equipment Corp. Some of these models are: Models 1000, 3000 and 3050.

PRESSURE BOMB MODEL 1000

PRESSURE BOMB MODEL 3000

PRESSURE BOMB MODEL 3005

Despite the different models, the basic structure is similar among all pressure bomb instruments. Their most important parts are: a stainless steel pressure vessel to hold the sample, a high pressure supply tank, a valve system and the chassis, and the red-out pressure test gauge.