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Gas exchange and growth responses to elevated CO 2 and light levels in the CAM species Opuntia ficus‐indica
Author(s) -
CUI M.,
NOBEL P. S.
Publication year - 1994
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1994.tb00322.x
Subject(s) - cladodes , photosynthesis , chemistry , dry weight , sugar , crassulacean acid metabolism , horticulture , botany , stomatal conductance , chlorophyll , zoology , cactus , biology , food science
Gas exchange and dry‐weight production in Opuntia ficus‐indica , a CAM species cultivated worldwide for its fruit and cladodes, were studied in 370 and 750 μmol mol −1 CO 2 at three photosynthetic photon flux densities (PPFD: 5, 13 and 20 mol m −2 d −1 ). Elevated CO 2 and PPFD enhanced the growth of basal cladodes and roots during the 12‐week study. A rise in the PPFD increased the growth of daughter cladodes; elevated CO 2 enhanced the growth of first‐daughter cladodes but decreased the growth of the second‐daughter cladodes produced on them. CO 2 enrichment enhanced daily net CO 2 uptake during the initial 8 weeks after planting for both basal and first‐daughter cladodes. Water vapour conductance was 9 to 15% lower in 750 than in 370 μmol mol −1 CO 2 . Cladode chlorophyll content was lower in elevated CO 2 and at higher PPFD. Soluble sugar and starch contents increased with time and were higher in elevated CO 2 and at higher PPFD. The total plant nitrogen content was lower in elevated CO 2 . The effect of elevated CO 2 on net CO 2 uptake disappeared at 12 weeks after planting, possibly due to acclimation or feedback inhibition, which in turn could reflect decreases in the sink strength of roots. Despite this decreased effect on net CO 2 uptake, the total plant dry weight at 12 weeks averaged 32% higher in 750 than in 370 μmol mol −1 CO 2 . Averaged for the two CO 2 treatments, the total plant dry weight increased by 66% from low to medium PPFD and by 37% from medium to high PPFD.