Premium
CO2 Exchange of Subterranean Clover in Variable Light Environments 1
Author(s) -
Wilson D. R.,
Fernandez C. J.,
McCree K. J.
Publication year - 1978
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1978.0011183x001800010006x
Subject(s) - photoperiodism , daytime , photon flux , atmospheric sciences , flux (metallurgy) , photosynthesis , latitude , trifolium subterraneum , biology , zoology , botany , horticulture , diurnal temperature variation , nocturnal , agronomy , ecology , pasture , photon , physics , chemistry , organic chemistry , quantum mechanics , astronomy
An experiment was designed to compare the CO 2 balances of communities of subterranean clover ( Trifolium subterraneum L.) plants exposed to variable and constant photon fluxes. Their CO 2 exchange rates (CER) were monitored continuously during a 4‐day test. During 2 of those days the communities were exposed to photosynthetic photon flux densities (PPFD) which were varied over the range 0.26 to 2.00 mE(einsteins) .s −1 .m −2 in a pattern that simulated the diurnal pattern of a clear day at latitude 30°. During the other 2 days the PPFD was constant at 1.20 mE.s −1 .m −2 . The photoperiod was 12 hours throughout. The PPFD was adjusted so that the integrated totals of CO 2 taken up during the daytime (D) were identical for the two treatments. The daytime CO 2 uptake patterns were different, reflecting the differences in PPFD distribution. The patterns and the totals of CO 2 released during the night‐time (N) were found to be almost identical for the two treatments. Consequently, the diurnal CO 2 balance (D‐N) of the plants was not affected by the different patterns of photon flux. Therefore, the normal practice in controlled environment studies of using a constant photon flux level throughout each photoperiod produces carbon balance data which are also valid in environments with variable photon fluxes.