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CHANGES WITH AGE IN THE PHOTOSYNTHETIC AND RESPIRATORY COMPONENTS OF THE NET ASSIMILATION RATES OF SUGAR BEET AND WHEAT
Author(s) -
WATSON D. J.,
WILSON J. H.,
FORD MARGARET A.,
FRENCH S. A. W.
Publication year - 1966
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1966.tb05973.x
Subject(s) - photosynthesis , sugar beet , sowing , photoperiodism , respiration , sugar , assimilation (phonology) , biology , zoology , agronomy , horticulture , botany , linguistics , philosophy , biochemistry
S ummary The net assimilation rates ( E ) of sugar beet and wheat growing in a controlled environment, and their components, the rates of photosynthesis ( P ) and respiration ( R ) of the whole plant per unit leaf area, were determined at intervals by a method described previously that depends on measuring the decrease in E when photosynthesis is prevented on some days during an experimental period by keeping plants in darkness. An alternative method of changing the duration of photosynthesis, by shortening the daily photoperiod, gave estimates of P and R almost identical with those obtained by shading plants throughout some days. In a period of 50 days from sowing for wheat and 90 days for sugar beet, E decreased by about a half. The value of P was always much greater than R ; the smallest ratio of P to R was 5. Most of the decrease in E with age was caused by decrease in P , and the change in R with age was relatively small. At 30 days after sowing, E of sugar beet was twice that of wheat, wholly because of difference in P . These experiments confirm that, except perhaps in extreme conditions, change in E can safely be attributed to change in photosynthetic rate.