Effects of a natural source of very high CO₂ concentration on the leaf gas exchange, xylem water potential and stomatal characteristics of plants of Spatiphylum cannifolium and Bauhinia multinervia

Abstract

The effect of a very high CO2 mole fraction (27000–35000 μmol mol−1) on photosynthesis and water relations was studied during the dry and the rainy season in plants of Spatiphylum cannifolium (Dryand.) Schott and Bauhinia multinervia (H.B.K.) DC. growing near natural cold CO2 springs. Xylem water potential in plants of both species was lowered by drought, high CO2 growth‐concentration decreasing it further in S. cannifolium. In plants of both species growing under high CO2 concentration photosynthetic rates measured at a CO2 mole fraction of 1000 μmol mol−1 were higher than in plants growing at ambient CO2 mole fraction and measured at 350 μmol mol−1. The response was the result of a direct effect of CO2 on the photosynthetic machinery. Changes in carboxylation efficiency in response to high CO2 were found during the rainy season, with an increase in S. cannifolium and a decrease in B. multinervia; a significant interaction between growth CO2 concentration and season in B. multinervia resulted from significant effects of both factors. An increase in intrinsic water‐use efficiency due to high CO2 was determined in both species by an increase in photosynthetic rate as well as a decrease in leaf conductance. In high‐CO2 plants of S. cannifolium a 71% decrease in stomatal density and 73% in stomatal index suggested that CO2 affected stomatal initiation, whereas in B. multinervia an 85% decrease in stomatal index and a 72% decrease in stomatal density indicated that CO2 influenced stomatal initiation as well as epidermal cell expansion. Our results indicate that very high CO2 concentrations did not inhibit photosynthesis in these species, and that growth under high CO2 allowed plants to attain carbon balances higher than those of plants growing under low CO2. This was particularly so during the dry season, since the photosynthetic rates at the corresponding ambient concentration were higher in plants nearer the springs, and carboxylation efficiency and some stomatal characteristics of both species apparently acclimated to high CO2, but patterns were not consistent and bore no obvious relationship to photosynthetic capacity.

Effects of atmospheric CO2 concentration, irradiance, and soil nitrogen availability on leaf photosynthetic traits of Polygonum sachalinense around natural CO2 springs in northern Japan

“…Most previous studies have investigated the effect of CO 2 on plant traits by making pairwise comparisons between high CO 2 sites around the springs and nearby control sites (e.g., Körner and Miglietta 1994;Jones et al 1995;Cook et al 1998;Fernandez et al 1998;Tognetti et al 1998;Stylinski et al 2000;Onoda et al 2007). However, environmental factors such as irradiance and soil N availability often vary widely in natural environments and can directly influence plant traits.…”

Long‐term relationships among atmospheric CO2, stomata, and intrinsic water use efficiency in individual trees

“…Making imprints using nail polish is a common technique for examining stomata and is particularly suitable for sampling delicate herbarium specimens in a nondestructive manner (e.g., Fern á ndez et al, 1998 ;Miyazawa et al, 2006 ). When possible, we measured each leaf ' s length and width, so that we could later determine whether any changes in stomatal density were related to leaf size.…”

Effect of atmospheric CO2 enrichment on the establishment of seedlings of Jatobá, Hymenaea Courbaril L. (Leguminosae, Caesalpinioideae)

“…Altogether, these effects should result in an increase in growth, but on the other hand, such an "efficiency effect" may be not be reached in all cases because of acclimation of photosynthesis (Bowes 1996). Plants grown in elevated CO environments may 2 exhibit photosynthetic acclimation or down regulation, which is characterised by reduced rates of photosynthesis resulting from decreased activity and/or amount of RUBISCO (Fernandez et al, 1998;Garcia et al, 1998, Ludewig et al, 1998. CO -induced photosynthetic 2 acclimation often results from insufficient plant sink strength, which can lead to carbohydrate accumulation in source leaves and the triggering of photosynthetic end product feedback inhibition (Gesch et al, 1998;Reekie et al, 1998).…”