Temperature and photon flux density effects on carbon assimilation in cranberry

摘要

The effect of temperature and radiation on cranberry (Vaccinium marcrocarpon Ait.) photosynthesis is not well understood. When C3 plants such as cranberry are exposed to optimal temperature and saturating light, the rate of net CO2 assimilation is almost always limited by rubisco due to the tendency for photorespiration. It is not clear whether new cranberry cultivars, whose fruit yields are greater than those of older cultivars, support the increased fruit load by the minimization of photorespiration or by having a larger photosynthetic capacity and better partitioning of assimilates between vegetative and reproductive sinks. This project evaluated the effect of temperature and photosynthetic photon flux density (PPFD) on net CO2 assimilation (A) in two old cultivars ('Early Black' and 'Stevens') and two new cultivars ('Crimson Queen' and 'Mullica Queen'). Gas exchanges of upright shoots were measured and data for all cultivars were taken at two cuvette temperature regimes (20 and 30°C). At 30°C, 'Mullica Queen' reached a net C02 assimilation rate of 25 pmol nr2 s1 at PPFD of 600 pmol nr2 s1. Dark respiration ranged from -10.75 pmol nr2 s1 at 30°C in 'Stevens' to 10.14 pmol m2 s1 at 20°C in 'Crimson Queen'. The highest light compensation point was 65.09 pmol nr2 s1 with 'Early Black' and the lowest was 9.96 pmol nr2 s1 with 'Stevens' at 20°C. The fact that 'Crimson Queen' reached a higher asymptote compared to the old cultivars at 30°C indicates a higher quantum yield and can capitalize onexisting light microclimates in the field. In a crowded canopy these differences could be significant with respect to net CO> assimilation.