Photosynthesis and Translocation of Recently Assimilated Carbon in Vegetative and Dormant Stages of Strawberry Plants

Abstract

Photosynthesis and translocation and distribution of photosynthates in ‘Donner’ strawberry plants were investigated, extending from the stage of vegetative growth to that of imposed dormancy.
1. Photosynthetic capacity of individual leaves decreased little until the deepest stage of true dormancy, as compared with the stage of vegetative growth. While, photosynthetic capacity of intact plants at and after the deepest stage of true dormancy decreased to one third or lower of that at the vegetative stage. This decrease was almost parallel with that of total leaf area. The contribution rate of each of the 3 upper unfolded leaves, except the uppermost one, was 20-25% and higher than the rates of the lower leaves.
2. When plants were kept for 15h in a glasshouse without heating after being fed with ¹⁴CO₂, respiratory loss of assimilated ¹⁴C decreased gradually from 70-54% at the stage of vegetative growth to 31% at the stage of imposed dormancy. Also, the total accumulation and translocation of ¹⁴C into sinks decreased from 21 and 45% at the stage of induction of dormancy to 15 and 22% at the stage of imposed dormancy. When plants were kept at 18°C after feeding, the values of such parameters changed little with the time of feeding.
3. The distribution pattern of ¹⁴C was affected little by the temperature during translocation, and seemed to be influenced mainly by the relative strength of sinks. Thus the percentage distribution to young leaves was high during vegetative growth and decreased towards the stage of imposed dormancy, while the percentage distribution to the roots changed inversely to that at the vegetative stage. In bearing plants, however, flower clusters behaved as stronger sinks than roots.
4. Amounts of ¹⁴C accumulated in the respective sinks were influenced mainly by the total ¹⁴C assimilated by the source leaf, rather than by the percentages accumulated or distributed to the sinks. Thus ¹⁴C was accumulated in large quantities in the respective sinks from the stage of vegetative growth through induction of dormancy, when ¹⁴C accumulated in the leaves exceeded that in the roots, reaching about half of ¹⁴C assimilated. But at and after the deepest stage of true dormancy, when total accumulation decreased, ¹⁴C accumulated in the leaves decreased markedly, while nearly half of the total was still distributed to the roots.