A Comparative Study of Gradual and Abrupt Changes in Root Temperature on Water Absorption

Abstract

IntroductionThe effects of low root temperature on various plant processes have long been known and extensively studied. It is generally recognized that one of its important effects is the reduction in water absorption of the plant; and the nearer the root temperature approaches the freezing point of water, the greater this effect will be manifested. The change in physical state, particularly the increase in viscosity with the decrease in temperature, of both water and protoplasm are undoubtedly two basic factors influencing water absorption at low root temperatures. The reduction in water absorption will affect other plant processes, directly or indirectly, to a greater or smaller degree depending on the extent of water shortage within the plant, and consequently may result in corresponding injury to the plant. Conditions favorable to high transpiration have been reported to bring about wilting and injury to the plant from desiccation when its roots are subjected to low temperature. However, different plant species appear to differ in their capacity to withstand the effects of low root temperature. KRAMER (7) observed that species which grow in the winter and species native to cooler climates are less affected by low soil temperature than warm-weather species. The statement by KRAMER (7), which will be discussed later, that plants cooled slowly wilted less severely than plants cooled rapidly, seems to be the only report in the literature on the comparative effects of rates of lowering root temperature. Under natural conditions, the change in temperature varies not only in respect to the level to which the temperature falls but also in the rate at which it occurs. Information regarding the effects of different rates of temperature decrease seems at the present to be limited, and it was the purpose of this investigation to compare the effect on water absorption of an abrupt decrease in root temperature with a gradual decrease in root temperature.

Photosynthesis in Sitka Spruce (Picea sitchensis (Bong.) Carr. IV. Response to Soil Temperature

“…The observation that no reduction in the rates of photosynthesis or transpiration occurred in Sitka spruce until the soil temperature was below 10C contrasts with many previous studies on other species (Kramer 1940(Kramer , 1942Kozlowski 1943;Bohning & Lusanandana 1952;Abdel Rahman, Kuiper & Bierhuizen 1959;Brouwer 1961;Ehrler 1963;Kuiper 1964;Cox & Boersma 1967;Babalola et al 1968;Benecke 1971;Havranek 1972;Rutland & Pallas 1972;Janes 1973), but is in agreement with two recent studies in which no reduction in photosynthesis or transpiration was observed at soil temperatures of 3YC, or above, in Scots pine and Norway spruce (Linder 1973) and in a diverse range of species of vascular plants (Anderson & McNaughton 1973). Differences amongst species have been interpreted as showing that the permeability of the roots is reduced to different extents by low temperature (Kramer 1969).…”

Effects of Low Soil Temperature on Transpiration, Photosynthesis, Leaf Relative Water Content, and Growth Among Elevationally Diverse Plant Populations

“…Doring's (1935) is the only previous report of species showing no reduction in water transport at very low root temperatures. Kramer (1940Kramer ( , 1942, Kozlowski (1943), Bohning andLusanandana (1952), Abd El Rahman et al (1959), Kuiper (1964), and Cox and Boersma ( 1967) reported decreases in transpiration accompanying decreases in root temperature in several plant species. These studies suggest a greater effect of low soil temperature upon transpiration than was found in the present investigation.…”

“…The majority of previous studies dealing with water transport at low root temperatures have been conducted with hydroponic-grown plants (Doring 1935, Kramer 1940, Bohning and Lusanandana 1952, Abd El Rahman et al 1959, Kuiper 1964 * * Significant at P < 0.01 *** Significant at P < 0.001 Brouwer 1965, Cox andBoersma 1967). This technique virtually eliminates temperature gradients in the root medium.…”

“…It would be difficult to distinguish between water-stress effects and other effects resulting from impaired root growth, mineral nutrition, or root metabolism in long-term, low-temperature experiments. Bohning and Lusanandana (1952) have shown that plants subjected to abrupt cooling of the roots developed more severe water stress than those subjected to gradual cooling. In the present experiments, soil temperatures were lowered rapidly, and a high evaporative demand was placed on the plants in an effort to maximize the effects of low soil temperature so that population differences might be more apparent.…”

Water Absorption of Alfalfa as Affected by Low Root Temperature and Other Factors of a Controlled Environment1

“…However, another factor may be involved. Low temperature at the lower soil depths may be limiting water absorption in two ways: ( 1) by retarding root growth, and ( 2) by directly depressing water transport through roots. The process of water absorption has physiological temperature limits, and plant species vary in their range of tolerance to adverse root temperatures.…”