ASGSB 1999 Annual Meeting Abstracts

LIGHT, ORYZALIN AND CALCIUM IN GRAVITY RESPONSIVE CAULONEMA. EB Tucker¹, DA Collings², E Johannes2, I Perez2, NS Allen2, WF Boss^{2 1}Natural Sciences, Baruch College, CUNY, NY; ²Botany Department, North Carolina State University, Raleigh, NC.

The objective was to study the involvement of calcium and microtubules in gravity perception by Physcomitrella patens dark grown caulonema. Bright field microscopy was used to observe and measure degree of bending, while calcium ratio imaging (Fura 2 and Calcium green-Texas red) was used to observed light effects on cytoplasmic calcium. Calcium channel blockers and cytoskeletal modifying agents were used to study the involvement of ion channels and microtubules. Small quantities of UV-A or blue (488 nm) and green (568 nm) light, inhibited gravi-induced bending and stimulated branch formation in distal cells. UV-A (340/360 nm) illumination stimulated a transient 1000 nM calcium wave that crossed the cell in 10 s. Results from manganese quenching and channel blocker studies, indicated an involvement of external calcium. Blue and green light (485-505/555-585 nm) evoked a sustained increase in cytosolic calcium at the tip and around the vacuole. 5-phosphatase, (to inactivate IP₃) microinjected into the cytoplasm, resulted in a rapid depletion of cytoplasmic calcium, particularly around the vacuole. Neither UV-A nor visible light inhibited the gravi-directed tip growth induced by oryzalin treatment. These tip growths were inhibited by calcium channel blockers.

This work was supported by NASA grant #NAGW-4984.

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