Figure 1.

Microinjection of cADPR into guard cell cytosol elevates [Ca²⁺]_cyt. (A) Typical results for the change in [Ca²⁺]_cyt after microinjection of cells, by using pipettes filled with ADPR or water, into the cytosol of fura-2-loaded guard cells of open stomata of C. communis (n = 5 and 2 cells respectively). Data shown are from a cell injected with ADPR. A transient increase in [Ca²⁺]_cyt was observed only during the 10-s current pulse. (B) Sustained increase in [Ca²⁺]_cyt following microinjection of cADPR into the cytosol of fura-2-loaded guard cells of open stomata of C. communis (n = 5 cells). [Ca²⁺]_cyt remained elevated for at least 10 min after the 10-s current pulse. (C) Oscillations in [Ca²⁺]_cyt (amplitude, 200 nM; period, 3.75 min) occasionally observed following microinjection of cADPR into the cytosol of fura-2-loaded guard cells of open stomata of C. communis (n = 2 cells). For A–C bar = 5 min. (D) ADPR (data shown) or water injected into the cytosol caused no change in guard cell turgor (right-hand guard cell, arrowed). (E) In contrast, cADPR injected into the cytosol caused a reduction in guard cell turgor (right-hand guard cell, arrowed). (Bars in D and E = 5 μm.)