Effect of elevated CO2 and spectral quality on whole plant gas exchange patterns in tomatoes

Abstract

In controlled environment plant production facilities, elevating either light or CO2 levels generally has led to increased biomass and yield due to enhanced canopy photosynthesis. Today, advancements in light-emitting diodes (LEDs) have made this technology a viable option for both supplementary lighting in greenhouses and a sole lighting source in controlled environment chambers. Our study used tomato plants grown under both ambient CO2 (AC) and elevated CO2 (EC) conditions then exposed them to various CO2 and lighting treatments during both whole plant and leaf level measurements. Plants grown under EC reached the first flower developmental stage 8 days sooner and were approximately 15cm taller than those grown under AC. However, under AC plants had more leaf area while their dry weights were similar. Of note, under EC chlorophyll a and b were lower, as were carotenoids per unit leaf area. Whole plant analyses, under all CO2 challenges, showed that plants exposed to high-pressure sodium (HPS), red-blue LED, and red-white LED had similar photosynthesis, respiration, and daily carbon gain. Under different light qualities, day-time transpiration rates were similar among CO2 conditions. Day-time water-use efficiency (WUE) was higher in plants grown and exposed to EC. Similarly, WUE of plants grown under AC but exposed to short-term elevated CO2 conditions was higher than those grown and tested under AC during all light treatments. Under all CO2 conditions, plants exposed to red-white and red-blue LEDs had lower WUE than those exposed to HPS lighting. Assessing alterations due to CO2 and light quality on a whole plant basis, not merely on an individual leaf basis, furthers our understanding of the interactions between these two parameters during controlled environment production. Principle component analyses of both whole plant and leaf data indicates that increasing CO2 supply has a more dramatic effect on photosynthesis and WUE than on transpiration.

Increased CO2 and light intensity regulate growth and leaf gas exchange in tomato

“…). It also confirms (Lanoue et al ) that Pn leaf and Pn Chl respond differently to increased CO 2 concentrations and increased light intensity. That is, the effect of increased CO 2 on Pn Chl was less than Pn leaf .…”

“…There are many routes through which increased CO 2 and light intensity may regulate Pn. These include effects on leaf pigments (Pérez‐López et al ), leaf mineral content (Li et al ), water use (Lanoue et al ) and Calvin cycle enzyme activity (Yu and Wang ), AQY and CE (Faralli et al , Jiang et al ). Potentially, all these result in higher dry mass accumulations and therefore faster growth (Li et al ).…”

“…This makes WUE leaf different from WUE plant . Lanoue et al () reported that day‐time average Pn leaf and Pn plant presented different patterns among various CO 2 treatments. It may be that because transpiration rate on a per leaf basis under elevated CO 2 was lower than under ambient CO 2 on a per plant basis.…”

“…It may be that because transpiration rate on a per leaf basis under elevated CO 2 was lower than under ambient CO 2 on a per plant basis. Also, the Pn leaf neglected the different leaf area among different treatments (Lanoue et al ).…”

“…The combination of increased CO 2 and increased light intensity can promote dry matter accumulation and carbon assimilation (Proietti et al , Naing et al , Li et al , Lanoue et al ). These effects may be due to a synergistic effect on Pn to produce more carbohydrates – but this needs further investigation.…”