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Gas exchange measurements required to predict the newly fixed carbon pool size in a source leaf of corn ( Zea mays L.)
Author(s) -
KOSHKIN E.,
TRETIAKOV N. N.
Publication year - 1990
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.1365-3040.1990.tb01286.x
Subject(s) - starch , darkness , photoperiodism , sucrose , photosynthesis , respiration , zoology , carbohydrate , chemistry , respiration rate , zea mays , botany , horticulture , biology , food science , biochemistry , agronomy
. Steady‐state photosynthesis (P n ), post‐illumination CO 2 release rates (R), sucrose‐phosphate synthase (SPS) activities, and levels of starch, sucrose and hexoses were measured in the source leaf of corn ( Zea mays L.) during a 16‐h photoperiod at 800 μmol m 2 s 1 . P n and SPS activity remained constant. Carbohydrate pools increased at a linear rate, except the first and last hour of the photoperiod. Both the CO 2 evolution rate at the moment of light removal (R max ) and SPS activity decreased by one half after the onset of darkness (0 60 min). Sucrose diminished during this period by 40%, whereas the starch remained constant. Thereafter, starch mobilization began, followed by a gradual decline in leaf respiration. The average dark export rate was calculated to be 60% less than that during the day. Maintenance respiration (R m ) of an attached leaf after 48 h darkness was determined. Plants were illuminated for different intervals (e.g. 5, 10 or 20 min), each followed by dark periods sufficient for respiration to decline to R m . The ratio of C assimilated in light to that released in dark was 6:1. After the 48‐h dark period, the minimal period of illumination (T min ) required to restore P n and R max to the original level was determined. A mathematical analysis of the kinetics involved in the recovery of P n and R max provided an estimate of turnover time (0.22h) and pool size 9.15 mmol m 2 ) for the newly fixed carbon.