2018 ASHS Annual Conference

Bell pepper, Capsicum annuum L., is one of several, highly-valued greenhouse crops. However, because they are non-climacteric, if bell peppers are harvested green, they stay green. For green peppers to turn red, the ripening process requires an extra 20 to 30 days on the plant. The aim of this study was to investigate source-sink dynamics during pepper ripening on- and off-plant. To examine the impacts on on-plant ripening, source-sink dynamics were altered by various levels of leaf removal and complete removal of the phloem when fruit were at either green or breaker. Physiological parameters such as fresh weight, firmness, colour, total carotenoids and chlorophylls were then measured at 0, 5, 10, 15 and 20 days after treatment (DAT). Compared with breaker-treated fruit, green fruit from plants where leaves and phloem had been removed showed a delay in the on-plant ripening process until 15 DAT. Furthermore, the greater the leaf removal rate, when fruit were green, the greater the delay to colour development and carotenoid content. Interestingly, phloem removal from plants when fruit were green not only significantly delayed the ripening process but also resulted in significantly higher fresh weight between 5 DAT and 15 DAT when compared to control fruit. Together, these results suggest important roles for sugar availability in on-plant pepper ripening. With 80% leaf removal having the greatest impact, this treatment was then selected to examine the effects on the behaviour of fruit during storage at 0, 6, 12 and 20 days after harvest. However, there was no effect of the preharvest leaf removal on any physiological parameter related to ripening during postharvest storage. Therefore, although source-sink dynamics appear to be important for pepper ripening on the plant, there may be other triggers for induction off the plant that require investigation.