PHOTOSYNTHESIS OF STRAWBERRY FRUIT

Photosynthesis of developing strawberry (Fragaria ananassa Duch.) fruit was examined.
After anthesis, the stomatal frequency of the fruit was maximum at 6 stomata mm^-2 and then decreased with surface expansion due to fruit development to 1-3 mm^-2, concomitantly with the loss of their regulatory properties at maturation, compared with 280-330 mm^-2 on the respective leaves.
Fruit transpiration of 7 mmol after anthesis exceeded that of the respective leaves (1.8 mmol) and then declined to 0.2 mmol H₂O m^-2 s^-1. Strawberry contained 128 kJoule energy per 100 g of fruit.
Efflux of CO₂ (respiration) from strawberry fruit of 1-4 µmol CO₂ m^-2 s^-1. provided the energy for metabolic conversions and exceeded CO₂ uptake under physiological conditions, resulting in an accumulation of 1-5% CO₂ in the intercellular spaces and a net CO₂ efflux from the fruit to the ambient 0.03% CO₂, i.e. in reverse order than in the leaf.
Both chlorophyll content (0.2-0.6 mg chlorophyll/g FM) and chlorophyll a:b ratio (2-3:1) of strawberry fruit were considerably (up to 7- fold less chlorophyll) lower than in the respective leaves with a chlorophyll ratio of 3-4:1 All these photosynthetic characters of strawberry fruit such as scarcity of stomata, accumulation of 1-5% CO₂ in the intercellular spaces, refixation of intercellular CO₂, CO₂ efflux from the fruit, scarcity of chlorophyll and closer chlorophyll a:b ratio, are different from these of the respective strawberry leaves and cannot be classified within an existing photosynthetic type, suggesting a different categorisation of strawberry fruit photosynthesis.

IV International Strawberry Symposium

M. Blanke

bioenergetics, carbon dioxide, chlorophyll, light reflection, light transmission, photosynthesis, CO₂ refixation, respiration, stomata, transpiration

https://doi.org/10.17660/ActaHortic.2002.567.81