Acclimation to High CO₂ in Bean

Abstract

ABSTRACIYoung bean plants (Phaseolus vulgaris L. cv Seafarer) grew faster in air enriched with CO2 (1200 microliters per liter) than in ambient CO2 (330 microliters per liter). However, by 7 days when increases in overall growth (dry weight, leaf area) were visible, there was a significant decline (about 25%) in the leaf mineral content (N, P, K, Ca, Mg) and a drop in the activity of two enzymes of carbon fixation, carbonic anhydrase and ribulose 1,5-bisphosphate (RuBP) carboxylase under high CO2. Although the activity of neither enzyme was altered in young, expanding leaves during the acclimation period, in mature leaves the activity of carbonic anhydrase was reduced 95% compared with a decline of 50% in ambient CO2. The drop in RuBP carboxylase was less extreme with 40% of the initial activity retained in the high CO2 compared with 50% in the ambient atmosphere. While CO2 enrichment might alter the flow of carbon into the glycolate pathway by modifying the activities of carbonic anhydrase or RuBP carboxylase, there is no early change in the ability of photosynthetic tissue to oxidize glycolate to CO2. Atmospheric CO2 enrichment has been used to increase the productivity and yield of many crops (1,10,11,17). Generally, CO2 enrichment increases total dry weight and yield when light, temperature, and water are not limiting growth. Elevated CO2 has the greatest impact on the plant organs developing during the treatment period (1,10,12). Experiments with soybeans (10) show that CO2 enrichment only increases yield when applied during reproductive growth and not when applied during vegetative growth. Older leaves seem less responsive to high CO2 than young leaves (1, 12), and differences between vegetatively growing plants in high and ambient CO2 diminish with prolonged treatment (1). Leaf thickness increases with high C02 treatment (17) which may bias area-based photosynthetic measurements. In addition, the effect of atmospheric CO2 on stomatal resistance varies by species (7,11 showed that photorespiratory rates were unaffected over a range of low to normal CO2 concentrations. At CO2 levels sufficient to saturate photosynthesis, a drop in O2 concentration from 21 % to less than 3% reduced net carbon fixation while at ambient CO2 levels, the low 02 concentration increased carbon fixation (20). Long term exposure to elevated CO2 atmospheres has been shown to alter enzyme complements. In tomato, high CO2 increases RuBP2 carboxylase and depresses glycolic acid oxidase activities (12) while in cotton, RuBP carboxylase activity is suppressed by high CO2 treatment (27).When plants are grown in high C02, but assayed for net carbon fixation at ambient CO2 concentrations, their photosynthetic rate is lower than that of plants grown in air (1,7,13,17

The Cytoplasmic Carbonic Anhydrases βCA2 and βCA4 Are Required for Optimal Plant Growth at Low CO2

“…2). This GUS expression pattern for bCA2 coincides with the leaf CA activity levels reported in pea (Pisum sativum; and bean (Phaseolus vulgaris; Porter and Grodzinski, 1984) and also fits with the observed EST abundance in TAIR microarray data (Schmid et al, 2005;Winter et al, 2007;Ferreira et al, 2008) as well as RNAseq data (Table I). Our results are in contrast to those of Wang et al (2014), who observed little or no GUS staining in the leaf with their bCA2 promoter.…”

Root Restriction as a Factor in Photosynthetic Acclimation of Cotton Seedlings Grown in Elevated Carbon Dioxide

“…Efforts to understand the physiological nature of the photosynthetic decline in plants exposed to long-term elevated CO2 have focused on chloroplast damage due to excessive carbohydrate accumulation (6, 29), on feedback inhibition associated with low utilization of photosynthate (6,8,22,23), and on changes in Rubisco activity (20,22,30). Starch often accumulates in chloroplasts in response to longterm elevated CO2 (3,6,29).…”

Correlation of Carbonic Anhydrase and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Expression in Pea

“…Other reports have suggested that plant CA activity is regulated by light intensity and COz concentration, parameters known to influence levels of Rubisco activity (Reed and Graham, 1981). For example, in both cucumber and bean, levels of CA and Rubisco were reduced when plants were grown at elevated levels of COz (Porter and Grodzinski, 1984;Peet et al, 1986). Most recently it was noted that a decrease in Rubisco abundance obtained by rbcS antisense expression also resulted in a major decline in CA abundance, whereas other Calvin cycle enzymes were unaffected by the reduced Rubisco levels (Hudson et al, 1992).…”