Patterns of photoassimilate translocation between shoots in Chinese chestnut trees during flowering and fruit growth

摘要

This study was undertaken to elucidate the carbon partitioning from different current shoots and its influence on flowering and fruit growth in neighbouring shoot complexes during the flowering period and during rapid fruit growth, and to interpret the source-sink relationship of the natural cupule loads in Chinese chestnut (Castanea mollissima Bl.). C-13 labelling of single shoots was used to assess carbon relationships in branches. Results showed that fruit-bearing shoots preferentially use carbon resources and draw the current photosynthate from proximal shoots. C-13 was assimilated into staminate and vegetative shoots lacking pistillate flowers and cupules. It was then transferred as part of the photosynthetic product to neighbouring fruit-bearing shoots. When a fruit-bearing shoot is near a vegetative shoot or a staminate shoot, little C-13 moved outside the shoot. This shows that vegetative shoots are important sources of carbon and that the pattern of resource allocation is affected by the location of a strong carbon sink. In general, the proportion of C-13 was greatest in shoots with mixed inflorescences and cupules, intermediate in stems and least in fruiting shoots. Ripening flowers and cupules, which are strong carbon sinks, may draw large quantities of photosynthate from their own branch. The pattern of translocation of photoassimilates to proximal fruit-bearing shoots depends on the type of shoot. Carbon partitioning in different branch combinations showed that the movement of photosynthates into the sink organ was determined by the sink strength of the fruit.