Pollination Deficit: A Key Limitation of Fruit Set in Northward-Expanded Camellia Orchards

Northward expansion of economically essential plants is a vital strategy for enhancing agricultural productivity; however, it often results in reduced yields. This study systematically assessed the impact of translocating the high-value oilseed species Camellia hainanica from its native tropical habitat Sanya to the temperate cultivation area of Changsha, focusing on its reproductive processes, including flowering, pollination, and fruit development. Our findings revealed a 45-day delay in anthesis at the transplanted location, which was associated with notably lower average daily temperatures (7.89 °C in Changsha compared to 24.63 °C in Sanya) during the anthesis period. While floral longevity, stigma receptivity, and pollen viability remained comparable between sites, anther dehiscence was markedly delayed by three days after transplanting. Crucially, pollinator visitation during peak flowering plummeted by 92% compared to the levels in Sanya, and a 57% reduction in pollen deposition on stigmas occurred. Consequently, natural fruit sets in Changsha collapsed to 0%, significantly lower than those in Sanya, despite artificial cross-pollination achieving an 11% fruit set rate. These results and the pollination deficit coefficient (D = 1.00) all demonstrate that severe pollination deficits are the key limitation causing reproductive failure in northward-expanded C. hainanica orchards. Addressing these yield constraints necessitates targeted breeding for earlier flowering genotypes and implementing pollination management strategies.