Using intracellular pH to evaluate growth inhibition of strawberry plants

At present, many strawberry plants (Fragaria x ananassa Duch.) are cold-stored in autumn and replanted the next summer to provide good crops the following spring. These plants should be dormant (low growth potential) with abundant nutrient reserves (e.g. carbohydrates) to withstand storage. Because no rapid test was available to assess the induction of autumnal dormancy of strawberry plants, we have evaluated the level of relative nutrient deficiency of growth organs (correlative inhibition, one cause of dormancy) by intracellular pH measurements on Elsanta strawberry plants. To control the validity of this evaluation, carbohydrate accumulation in the storage parenchyma was measured and the dormancy level was estimated by measuring the petiole length of Elsanta plants under controlled conditions. The results showed that petiole length and intracellular pH of buds were low at the beginning of autumn, implying that the measurements of intracellular pH can be a marker of dormancy induction in strawberry plants. Then, in the middle of autumn, when the first changes occurred, growth inhibition remained even as the intracellular pH measurements implied a break of correlative inhibition. This should suggest that another growth inhibition remains after the first chilling.