ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

Calvin cycle activity in fruit and the effect of heat stress.

Smillie, R. M.;

Scientia Horticulturae Year: 1992 Vol: 51 Issue: 1-2 Pages: 83-95 Ref: 17 ref.

1992

บทคัดย่อ

As green fruits mature the permeability of the outer epidermis decreases. Consequently, gas exchange with the outside air becomes more restricted and it is unclear whether or not maturing fruits continue to fix CO2 photosynthetically, possibly utilizing accumulated internal CO2. To examine this, Calvin cycle activity in fruits was investigated by chlorophyll a fluorescence quenching in vivo, the fluorescence emission from the fruit surface being measured with a modulated fluorometer. Fruits of 15 species (Vaccinium corymbosum, pummelos, feijoas, figs, guavas, kiwifruits, lemons, West Indian limes, Litchi, mandarins, oranges, pears, persimmons, tomatoes and avocados) were examined and all showed evidence of Calvin cycle activity as indicated by relaxation of chlorophyll fluorescence quenching. Allowing for the differences in chlorophyll content, the activity in fruits was comparable with that in leaves. When exposed to CO2-free air, tomato leaves and discs of avocado peel quickly lost activity, but loss of activity was slow in intact fruits, indicating that most of the CO2 fixed photosynthetically in fruits was derived from CO2 accumulated within the fruit. Calvin cycle activity in fruits was especially sensitive to heat, more so than either photosynthetic electron transfer activity or photophosphorylation. Optical monitoring of Calvin cycle activity by fluorescence quenching thus has the potential to detect early symptoms of heat stress in fruits, for instance, as the result of postharvest heat treatments to disinfest fruits of insects.