Light and Temperature Regulation of Early Morning Crassulacean Acid Metabolism in Opuntia erinacea var Columbiana (Griffiths) L. Benson

Abstract

During the early morning period, light and temperature exert distinctively different influences on the gas exchange patterns of the Crassulacean acid metabolism plant Opuntia erinacea through their effects on acid metabolism. An initial decrease in CO2 uptake was triggered by illumination and was apparently due to a decreased CO2 diffusion gradient through light-mediated decarboxylation of malate. In contrast, the morning burst of CO2 uptake occurred at high temperature presumably in response to increases in both stomatal conductance and the CO2 diffusion gradient, resulting from the temperature-regulated fixation of endogenous CO2, primarily into malate. Subsequent stomatal closure, apparently due to elevated levels of internal CO2 through rapid decarboxylation of malate at high temperature, was primarily responsible for the final termination of early morning Crassulacean acid metabolism.The initial burst ofCO2 uptake during phase II (early morning) CAM is the most characteristic physiological feature of the early morning period in plants which exhibit CAM (10). MATERIALS AND METHODSPlant Material. Single cladophylls of Opuntia erinacea var columbiana (Griffiths) L. Benson were collected from a native population in eastern Wahington State and prepared for experimentation as described previously (7).Gas Exchange Measurements. Whole plant CO2 exchange was measured using an open IR gas analysis system as described previously (8). Ingoing CO2 and 02 concentrations were maintained at 330 Wl/l and 21%, respectively, by mixing gases from cylinders containing 21% 02 in N2, and 1% CO2 in N2 using Wosthoff mixing pumps. All night time measurements were made at 15TC and four morning treatments included measurements at 35C in the light (control), 150C in the light, and 15TC and 35C in continued darkness. Illumination during the light treatments was provided by a GE 1,000 w multivapor lamp and four Sylvania 300 w flood lamps after filtration through 18 cm ofwater. The resulting photon flux density and TR3 were similar to those used for growth. Stomatal conductance values were calculated from water vapor concentrations which were continuously monitored with a dew point hygrometer (EG&G, model 880), and cladophyll surface areas were estimated using a leaf area meter (Lambda, model LI-300).Malate and Titratable Acidity Determinations. Malate and titratable acid concentrations were determined, as previously described (7), for plants subjected to experimental treatments identical to those used for measuring gas exchange. RESULTSCarbon Dioxide Exchange and Stomatal Conductance. The CO2 exchange patterns for the plants measured under the four temperature/light (dark) treatments revealed basic differences in the effects of light and temperature (Fig. 1A). An

Red and blue light ratio affects the growth and quality of edible cactus (Nopalea cochenillifera)

“…Light is essential for plant growth, with both wavelength and intensity affecting plant growth and morphogenesis (Yanagi et al, 2006;Mortensen and Stromme, 1987). Studies have shown that light intensity affects the elongation of the cactus stem and the malate content of cladodes (North et al, 1995;Littlejohn et al, 1985). However, to our knowledge, few studies have investigated the relationship between the light environment and growth of edible cacti (North et al, 1995).…”

Effects of Light Wavelength on Daughter Cladode Growth and Quality in Edible Cactus Nopalea cochenillifera Cultured in a Plant Factory with Artificial Light

“…Hydroponics is used as a basic cultivation system in plant factories, which are horticulture greenhouses or automated facilities where vegetables and other crops can be produced throughout the year by controlling the environmental conditions, such as light, temperature, humidity, CO2, and nutrient availability (Hirama 2015;Yanata & Takata 2014). Light is essential for plants, with both the wavelength and intensity affecting plant growth and morphogenesis (Mortensen & Strømme 1987;Yanagi et al 2006), and previous studies have shown that light intensity affects the elongation growth of the stems and the malate content of the cladodes in cacti (Littlejohn & Ku 1985;North et al 1995). However, few studies have investigated the relationship between the light environment and cladode growth in edible cacti, an understanding of which is important for improving the production and quality of these crops.…”