Fig. 8

A proposed model for parthenocarpy in cucumber. Proposed model illustrating the working hypothesis of parthenocarpy, which can be promoted by either hormone-dependent or -independent pathways. The hormone-unassociated stimulations may be regulated by the NP-specialized proteins (Table 2) because of their hormone-insensitive expression characteristics. In the presence of sufficient hormone levels (endogenous or exogenously supplied), the parthenocarpic young fruits can continue to grow. However, in the absence of hormones, hormone-dependent parthenocarpic fruits will return to the fruit abortion pathway, while the hormone-independent parthenocarpic fruits will stay in a dormant growth state that may be caused by abortion-inhibiting proteins. Whether the dormant fruits can restart growth or be artificially induced remains unclear. ‘+’: in the presence of hormones; ‘-’: in the absence of hormones. The plant images were taken by JL in a greenhouse of Jiangpu experimental station of Nanjing Agricultural University