A relationship between transpiration and soil suction and soil‐water content has been derived. Good agreement between the theory and results of laboratory experiments was obtained. The results suggest that once plants wilt, the transpiration rate should be roughly proportional to the available water content of the soil. The lower limit of water available for transpiration occurs at a suction well above 15 bars.

No abstract

The thermocouple psvchromiieter (leveloped by Richardls and Ogata (1)

Synopsis An equation describing the uptake of water by plants is described. Greenhouse experiments support the equation and show that the lower limit of water availability is determined by the rate of water transmission through the soil to the plant roots. An appreciable amount of water is shown to move vertically in the root zone.

Climatological factors and the boll load from the first fruiting cycle were evaluated as primary causes for low boll retention by cotton (Gossypium hirsutum L.) during midseason. Boll retention was permitted from incipient flowering, or after June 26, July 15, July 30, or August 14, by the daily removal of flowers. Boll retention was greater than 75% initially, but decreased to less than 50% after bolls equivalent to 500 to 1,200 kg lint/ha (1 to 2 bales/acre) were retained and less than 20% after bolls equivalent to 700 to 1,300 kg lint/ha (1.25 to 2.25 bales/ acre) were retained. The fruit load was the primary cause for low boll retention and cessation of flowering during midseason. No direct relationship between low boll retention and high maximum or minimum temperatures or high relative humidity was observed.