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Effects of plant water deficit on the daily carbon balance of leaves of cacao seedlings
Author(s) -
Deng Ximin,
Joly Robert J.,
Hahn Daniel T.
Publication year - 1989
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1989.tb05661.x
Subject(s) - theobroma , respiration , carbohydrate , horticulture , photoperiodism , chemistry , zoology , botany , agronomy , biology , organic chemistry
The daily carbon balance of individual source leaves of Theobroma cacao L. seedlings was measured at 2‐ to 3‐day intervals during a 19‐day period of increasing plant water deficit and during an 8‐day period of recovery following rewatering. In each case, responses of stressed seedlings were compared to those of irrigated controls. Leaves of irrigated cacao seedlings assimilated approximately 41 mg carbohydrate dm ‐2 during 12‐h photoperiods, and exported an average of 34 mg carbohydrate dm ‐2 during 24‐h measurement cycles. The rate of carbon export from cacao leaves was sharply reduced as leaf water potential (ψ) declined between ‐0.8 and ‐2.0 MPa. Further, the rate of export was closely associated with the net assimilation rate (A), with export capacity being severely reduced as A fell to near zero. Net accumulation of dry matter occurred as long as A remained greater than approximately 20 mg carbohydrate dm ‐2 over the 12‐h photoperiod, but at lower assimilation rates, export exceeded concomitant assimilation. Carbon export continued at the expense of leaf carbon reserves as photoassimilation fell to near zero during periods of severe water stress (ψ < ‐2.0 MPa). Night respiration rate was independent of plant water status.