ISHS Acta Horticulturae 567: IV International Strawberry Symposium
PHOTOSYNTHESIS OF STRAWBERRY FRUIT |
| Author: | M. Blanke |
| Keywords: | bioenergetics, carbon dioxide, chlorophyll, light reflection, light transmission, photosynthesis, CO2 refixation, respiration, stomata, transpiration |
| Abstract:
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. | |
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