Jp. Prive et al., SEASONAL-CHANGES IN NET CARBON-DIOXIDE EXCHANGE-RATES OF AUTUMN-BLISS, A PRIMOCANE-FRUITING RED RASPBERRY (RUBUS-IDAEUS L.), Canadian Journal of Plant Science, 77(3), 1997, pp. 427-431
Seasonal changes in leaf net carbon exchange rate (NCER), stomatal con
ductance (g(s)), and intercellular CO2 (ci) were determined for 2-yr-o
ld potted Autumn Bliss (Rubus idaeus L.) plants grown under field cond
itions. NCER varied inconsistently between leaves which subtended frui
ting lateral branches (laterals) and those that did not. in leaves wit
h fruiting laterals, it was lower on three dates, similar on three oth
er dates and once greater than in leaves without fruiting laterals. Ev
idence of nonstomatal inhibition of photosynthesis was also apparent a
s leaf NCER and g, fluctuated during the season while ci remained rela
tively constant. The leaf chlorophyll content increased when fruiting
laterals were present, but this did not produce a consistently higher
leaf NCER. The SPAD-501 meter provided a rapid and accurate, nondestru
ctive estimate of leaf chlorophyll content for Autumn Bliss red raspbe
rry leaves. Under uniform environmental conditions, all healthy, fully
expanded leaves along the primocane had the same photosynthetic poten
tial. Also, leaf age did not influence leaf gas exchange until the lea
ves started to senesce. Therefore, good light interception throughout
the canopy is needed to optimize dry matter production in primocane-fr
uiting red raspberries.