Long-term compound interest effect of CO2 enrichment on the carbon balance and growth of a leafy vegetable canopy

Autor: Koichi Nomura, Makito Mori, Akihiro Takada, Daisuke Yasutake, Takashi Okayasu, Takahiro Kaneko, Masaharu Kitano, Yukio Ozaki
Rok vydání: 2021
Předmět:
Zdroj: Scientia Horticulturae. 283:110060
ISSN: 0304-4238
DOI: 10.1016/j.scienta.2021.110060
Popis: The response of crops to elevated atmospheric CO2 concentrations ( C a ) is of great concern for horticultural vegetable production in greenhouse facilities, where C a levels are often artificially elevated. To elucidate the long-term effect of the elevated C a on canopy photosynthesis and growth, we conducted long-term continuous measurements of the canopy photosynthesis ( A ) and leaf area index ( L ) of hydroponically grown spinach canopies under elevated C a (approximately 800 μmol mol−1) and ambient C a (approximately 400 μmol mol−1) treatments by combining the open chamber method and image analysis of the top of view of canopies. There existed a positive feedback loop between A and L, where an increase in L caused an increase in A , which subsequently accelerated the increase in L . The enhancing effect of elevated C a on A, which was evaluated with enhancement ratios (i.e., A in the elevated C a treatment divided by A in the ambient C a treatment; A e l e v / A a m b ), showed a short-term increase under high-light conditions during the daytime and a long-term increase with canopy growth toward the harvest. The long-term increase in A e l e v / A a m b was attributed to the enhancement of A e l e v brought on by not only the short-term enhancing effect of elevated C a but also the more rapidly increasing and thus larger L in the elevated C a treatment compared with that in the ambient C a treatment. Both the long-term increase in A e l e v / A a m b and the more rapidly increasing L in the elevated C a treatment were caused by the “compound interest effect” of elevated C a , where the enhancing effects of elevated C a on A and L were gradually amplified over a long-term period through the positive feedback loop between A and L . This compound interest effect of elevated C a also caused a long-term increase in canopy nighttime respiration in proportion to daytime photosynthesis. Through these changes in the canopy-scale carbon balance, the compound interest effect detected in the elevated C a treatment likely contributed to a substantial increase in the final aboveground dry weight at the harvest time. This study highlights the importance of the long-term compound interest effect of elevated C a on canopy photosynthesis, carbon balance, and growth.
Databáze: OpenAIRE
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