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Photosynthetic characteristics of the leaves of ‘Golden Delicious’ appletrees
Author(s) -
WATSON R. L.,
LANDSBERG J. J.,
THORPE M. R.
Publication year - 1978
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.1365-3040.1978.tb00746.x
Subject(s) - photosynthesis , stomatal conductance , botany , horticulture , quantum yield , conductance , flux (metallurgy) , respiration rate , chemistry , respiration , mathematics , physics , biology , combinatorics , optics , fluorescence , organic chemistry
Using an open‐system leaf chamber, gas exchange measurements on attached leaves of 3‐4‐year‐old Golden Delicious apple trees, made through two seasons, provided data from which the parameters of a leaf photosynthesis model could be derived. The equation is:where C 1 is internal CO 2 concentration and Q p is the incident quantum flux. There was considerable leaf to leaf variation in the values of the parameters but no clear seasonal trends were established. The initial slope (a) had an average value of about 2.5 × 10 −3 mg μmol −1 † (i.e. quantum yield ∼ 0.057); the mesophyll conductance (g m ) was about 3.5 mm s −1 in extension leaves of trees carrying fruit and 2.5 mm s −1 in extension leaves of defruited trees. Differences between the values of g m for spur leaves with and without subtending fruits were not significant; 2.5 mm s −1 may be used. Dark respiration (R d , mg m −2 s −1 ) increased exponentially with temperature (T°C); R d ∼ 0.006 exp (0.09 T). At saturating photon flux density P n was linearly related to C i , up to C i ∼ 250 mg m −3 . Optimum temperatures for P n were slightly different in the two years and were in the range 16‐26°C.