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.