photosynthesis continuous monitoring system for CAM plants

Abstract

Diurnal CO 2 exchanges in crassulacean acid metabolism (CAM) plants are significantly different from those in C3 and C4 plants. The instantaneous short-time CO 2 exchange of a single leaf measured by commercial portable photosynthesis measuring systems with a small leaf chamber cannot reflect the plant photosynthetic capacity for CAM plants because of the CO 2 fixation property. Therefore, a photosynthesis continuous monitoring system with two canopy cuvettes was developed for measuring diurnal net CO 2 exchange rates for CAM plants. To evaluate stability and applicability of the photosynthesis continuous monitoring system, continuous measurement of net CO 2 exchange rates of plants with different photosynthetic pathways were conducted. An obligate CAM plant (Kalanchoe daigremontiana), four facultative CAM plants (Dendrobium officinale, D. chrysotoxum, D. nobile, and D. primulinum), a C3 plant (Strawberry, Fragaria ananassa), and a C4 plant (Corn, Zea mays) were selected as model plants. K. daigremontiana had a significant CO 2 absorption during the dark period and its net CO 2 exchange rates fluctuated around 0 μmol/(m 2 ·s) during the photoperiod in a growth chamber. Net CO 2 exchange rates of F. ananassa and Z. mays in a greenhouse gradually increased after sunrise, reaching a maximum at about 12:00, and then gradually decreased to negative values during the night time. It is interesting to observe that D. officinale in the greenhouse and growth chamber absorbed CO 2 during both day and night times. The photosynthetic pathways of D. chrysotoxum, D. nobile, and D. primulinum were also well distinguished by this photosynthesis continuous monitoring system. The results showed that the photosynthesis continuous monitoring system is capable for quantitative evaluation of diurnal net CO 2 exchange characteristics not only in the CAM plants but also in small size C3 and C4 plants with low net photosynthetic rates for long-time and high-accuracy measurements.

Modeling and simulation of temperature control system in plant factory using energy balance

“…This section presents the theoretical models of energy balance in closed plant production, further to deduce the mechanism model of a temperature control system, particularly for energy loads balance, crop transpiration, and artificial lighting in plant factories. In a building structure, there are non-uniform spatial distributions of temperature in the horizontal and vertical directions [29,30] , partly due to the combined influences of many factors, such as the internal environment, control mode, planting structure, and types of crops [31,32] . Nevertheless, the internal temperature in the plant factory can be assumed as a uniform spatial distribution in a specific research period, and then to establish the relationship between temperature and time.…”