Selective trans-cinnamic acid uptake impairs [Ca2+]cyt homeostasis and growth in Cucumis sativus L

To obtain insight into interspecies interactions mediated by allelochemicals, the response of cucumber (Cucumis sativus L. cv Jinyan No.4) and figleaf gourd (Cucurbita ficifolia Bouché) seedlings to trans-cinnamic acid (CA) (1) was investigated. While trans-CA is an autotoxin in cucumber root exudates, figleaf gourd is resistant to it. Cucumber, however, had a high rate of trans-CA uptake by the roots, leading to reduced root growth. The trans-CA treatment also resulted in an intracellular release of Ca(2+) from the vacuole to the cytoplasm, and, thus, an increased [Ca(2+)](cyt) level accompanied by gradual loss of cell viability in cucumber roots. Taken together, these results suggest that [Ca(2+)](cyt) homeostatic disturbance is one of the primary triggers for trans-CA phytotoxicity in cucumber.