Bicarbonate stimulates non‐structural carbohydrate pools of Camptotheca acuminata

Abstract

The role of root-derived dissolved inorganic carbon (DIC) has been emphasized lately, as it can provide an alternative source of carbon for photosynthesis. The fate of newly fixed DIC and its effect on non-structural carbohydrate (NSC) pools has not been thoroughly elucidated to date. To this end, we used C (NaHCO ) as a substrate tracer to investigate the incorporation of newly fixed bicarbonate into the plant organs and NSC compounds of Camptotheca acuminata seedlings for 24 and 72 h. NSC levels across the organs were all markedly increased within 24 h of labeling treatment and afterward only decreased in stems at 72 h. The variation range of NSC concentrations in roots was considerably smaller than in the stem and leaves. As time passed, the δ C in NSC compounds was significantly affected by C labeling and was more positive in the roots than in the stem and leaves. Starch was more C-enriched than was soluble carbohydrate, and the δ C of root starch was as high as -4.70‰. Bicarbonate incorporation into newly formed NSC compounds contributed up to 0.24% of the root starch within 72 h. These data provided strong evidence that bicarbonate not only acted as a C source that contributed slightly to the NSC pools but also stimulated the increase in NSC pools. The present study expands our understanding of the rapid change of NSC pools across the organs in response to bicarbonate.

Root-Zone CO2 Concentration Affects Partitioning and Assimilation of Carbon in Oriental Melon Seedlings

“…This study showed that when the 0.2%, 0.5% and 1% root-zone 13 CO 2 labeling treatments reached 24 h, δ 13 C in roots increased, and roots could absorb CO 2 . The absorbed CO 2 is transported upward to the stems and leaves as the substrate of photosynthesis, or is diffused directly from the leaves to the atmosphere, resulting in a reduction in 13 C in the roots [22] and decreasing the δ 13 C value in the roots after 24~72 h. Long-term high root-zone CO 2 treatment increases the concentration of CO 2 in root cells [37], which may reduce the ability of roots to absorb 13 CO 2 . Compared with 0.2% root-zone 13 CO 2 treat-ment, 13 C in the 0.5% and 1% treatments was absorbed by roots and transported upward, to a greater extent under the 1% treatment than the 0.5%.…”

“…CO 2 is transported from the roots to the stems and leaves, where 13 CO 2 flows out of the leaf surface and diffuses into the atmosphere [20,21]. The 13 C tracer of Camptotheca acuminate seedlings showed that the soluble inorganic carbon absorbed by roots could be used as a carbon source for photosynthesis, affecting the formation of photosynthates [22].…”

Species-Specific and Altitude-Induced Variation in Karst Plants’ Use of Soil Dissolved Inorganic Carbon

“…Recently, root-derived carbon sources supporting photosynthesis have reemerged as a hotspot in plant ecophysiological studies [15][16][17][18]. Research shows that 13 C-enriched CO 2 or HCO 3 − labeling in the root zones can be transported upward through the transpiration stream [19] and thus affects the carbon isotope composition (δ 13 C) of leaf photoassimilates and aboveground tissues [20,21]. Although these results are obtained from the manipulated experiments inside a laboratory, it may be applied to karst plants grown in the field, given the high concentration of bicarbonate contained in karst soils.…”