LEAF EMERGENCE, PHYSIOLOGICAL AND PHOTOSYNTHETIC CHARACTERISTICS IN FRUITED AND DEFLOWERED STRAWBERRY

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  • 1 Washington State University Research and Extension Unit, 1919 N.E. 78th St., Vancouver, WA 98665

After anthesis, date of leaf emergence was recorded in fruited plants (F) and deflowered plants (DF) of `Totem' strawberry (Fragaria × ananassa), which were grown in a randomized block design with four blocks in a greenhouse. Two different regression models were fitted to describe leaf emergence rate (LER) after anthesis for F and DF (R2 = 0.826 and 0.916, respectively). The LER of F decreased during the fruit development, and accelerated and exceeded DF after fruit maturity, then both dropped when the growth season was ending.

Physiological and photosynthetic characteristics were measured on leaves from F and DF at green fruit, red fruit, and after fruit maturity stages. Newly expanded leaves had significantly higher gas exchange rates, specific leaf weight, chlorophyll a and b contents but lower a/b ratio than the older leaves both during and after fruit development. They also had higher amplitudes of Ca 693 but lower peaks at Ca 684 and Cb 649 in their fourth-derivative chlorophyll spectra. Leaf chlorophyll a content and CO2 assimilation rate decreased after fruit maturity. Plants at red fruit stage had higher chlorophyll b content than at green fruit and after fruit maturity stages.

The LERs of the second and third leaves emerged after anthesis were most seriously affected by fruit development. They showed greater photosynthetic activity than other leaves in the canopy during fruit development and were thus important to fruit yield.

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