ISSN:
1365-3040
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Abstract 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: 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:01407791:PCE51:PCE_51_mu1"/〉where C1 is internal CO2 concentration and Qp 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 (gm) 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 gm for spur leaves with and without subtending fruits were not significant; 2.5 mm s−1 may be used. Dark respiration (Rd, mg m−2 s−1) increased exponentially with temperature (T°C); Rd∼ 0.006 exp (0.09 T). At saturating photon flux density Pn was linearly related to Ci, up to Ci∼ 250 mg m−3. Optimum temperatures for Pn were slightly different in the two years and were in the range 16-26°C.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-3040.1978.tb00746.x
