Leaf Diffusive Resistance and Water Economy in Carbon Dioxide‐enriched Rice Plants

Abstract

SUMMARYThe leaf diffusive resistance to the transfer of water vapour and COj exchange in rice plants {Oryza sativa L., cv. IR-20) measured from the late vegetative stage to maturity, varied in response to differing CO^ enrichments. The leaf diffusive resistance of plants treated with 900 /tl r* CO2 ranged from one-half to twice that of the control plants (330//ll"'CO2).This difference was more pronounced during the heading and ripening stages. In plants treated with 600 /tl ri CO2, the diffusive resistances appeared to be smaller than in the control plants for most of the day. In the diurnal cycles, resistances were highest during the early morning and before sunset, the maximum again occurring in the plants treated with 900 fi\ T' CO^.The rate of transpiration was inversely related to the diffusive resistance, and was 20 to 100 % lower in the plants treated with 900 //I T' COj than in the controls, both in the seasonal and diurnal cycles. In plants treated with 600 //11"' CO^, the rate of transpiration was lower than in the controls in the morning but distinctly higher during the afternoon. However, the integrated total daily transpiration in 600 /il T' CO2 did not exceed that of the controls. In all cases, COa-treated plants, through their increased biomass production and economic yield, appeared to have a higher water use efficiency than the control plants.

Plant water relations and the effects of elevated CO2: a review and suggestions for future research

“…These chambers can be placed outdoors to take advantage of natural light and temperature regimes (Jones et al 1984;Rogers et al 1984;Idso et al 1987;Szarek et al 1987), or closed chambers placed in greenhouses, where environmental factors are more readily controlled (Khan & Madsen 1986;Reekie & Bazzaz 1989;Arnone & Gordon 1990). Controlled environment rooms are frequently used to grow seedlings at enhanced Ca (e.g., Higginbotham 1985;Wray & Strain 1986).…”

“…In some cases in which drought stress was the focus, excised branches of mature trees have been placed in, and then removed from, a water bath as a means of imposing short-term water stress (Beadle et al 1979) In studies in which environmental conditions other than Ca were controlled, light intensity, or photosynthetically active radiation (PAR), was commonly maintained at moderate levels of 450 to 750 #E m -2 s-1 (Sionit et al 1981;Conroy et al 1988a;Sasek & Strain 1989). Some workers, however, grew plants at low light levels of less than 150 #E m -2 s 1 (Khan & Madsen 1986) and some at high light levels between 1000 and 2000 /~E m -2 s-1 (Rogers 1983;Tolley & Strain 1984a;Reekie & Bazzaz 1989), depending on plant material and objectives. Light sources were either fluorescent and incandescent bulbs (Sasek & Strain 1989), high intensity discharge lamps (Tolley & Strain 1984a), natural sun light (Rogers 1983;Reekie & Bazzaz 1989), or some combination of these sources (Khan & Madsen 1986).…”

“…Some workers, however, grew plants at low light levels of less than 150 #E m -2 s 1 (Khan & Madsen 1986) and some at high light levels between 1000 and 2000 /~E m -2 s-1 (Rogers 1983;Tolley & Strain 1984a;Reekie & Bazzaz 1989), depending on plant material and objectives. Light sources were either fluorescent and incandescent bulbs (Sasek & Strain 1989), high intensity discharge lamps (Tolley & Strain 1984a), natural sun light (Rogers 1983;Reekie & Bazzaz 1989), or some combination of these sources (Khan & Madsen 1986). Most workers used growing temperatures between 20 and 30 °C (Sionit et al 1981;Rogers 1983;Reekie & Bazzaz 1989;Sasek & Strain 1989).…”

“…The most widely used method for measuring the response of evaporative flux density (E), and thus leaf conductance (g0, to increased Ca appears to be steady state porometry (Rogers et al 1984;Sionit & Patterson 1985;Khan & Madsen 1986;Teskey et al 1986). In the steady state porometer, a given foliar area is placed into a cuvette, or chamber.…”