Publication Date

1985

Location

Kyoto Japan

Description

This paper reports a heat pulse method for measuring water flux in the stem and its application to investigation of plant-water relationships in Japanese millet (Echinochloa utilis Ohwi et Yabuno), sorghum (Sorghum bicolor L. Moench) and maize (Zea mays L.).

1). The velocity of sap-flow in the stem, evaluated by the heat pulse method, was closely ralated to the water loss due to transpiration measured in weight units. Linear relationships and positive correlations were observed in all species between sap-flow velocity and transpiration rates.

2). Japanese millet had similar pattern in the diurnal courses of the sap-flow velocity at different plant densities under field condition. The sap-flow velocity increased rapidly with increasing solar radiation in the morning, and reached highest level around midday, then declined gradually with decreasing solar radiation.

3). The sap-flow velocity was closely related to factors affecting transpiration, such as stomata! aperture, stomata! diffusion resistance, leaf temperature and solar radiation.

4). These results indicate that the heat pulse method is suitable for the study of water consumption by individual plants under field conditions.

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A Measurement of the Sap-Flow Velocity Using the Heat Pulse Method in Several Forage Crops

Kyoto Japan

This paper reports a heat pulse method for measuring water flux in the stem and its application to investigation of plant-water relationships in Japanese millet (Echinochloa utilis Ohwi et Yabuno), sorghum (Sorghum bicolor L. Moench) and maize (Zea mays L.).

1). The velocity of sap-flow in the stem, evaluated by the heat pulse method, was closely ralated to the water loss due to transpiration measured in weight units. Linear relationships and positive correlations were observed in all species between sap-flow velocity and transpiration rates.

2). Japanese millet had similar pattern in the diurnal courses of the sap-flow velocity at different plant densities under field condition. The sap-flow velocity increased rapidly with increasing solar radiation in the morning, and reached highest level around midday, then declined gradually with decreasing solar radiation.

3). The sap-flow velocity was closely related to factors affecting transpiration, such as stomata! aperture, stomata! diffusion resistance, leaf temperature and solar radiation.

4). These results indicate that the heat pulse method is suitable for the study of water consumption by individual plants under field conditions.