Transmembrane transport of K+ and Cl− during pollen grain activation in vivo and in vitro

Abstract

We studied the possibility of K + and Cl -efflux from tobacco pollen grains during their activation in vitro or on the stigma of a pistil. For this purpose the X ray microanalysis and spectrofluorometry were applied. We found that the relative content of potassium and chlorine in the microvolume of pollen grain decreases during its hydration and activation on stigma. Efflux of these ions was found both in vivo and in vitro. In model in vitro experiments anion channel inhibitor NPPB ((5 nitro 2 (3 phenylpropylamino) ben zoic acid) in the concentration that was blocking pollen germination, reduced Cl -efflux; potassium channel inhibitor TEA (tetraethylammonium chloride) partially reduced K + efflux and lowered the percent of acti vated cells. Another blocker of potassium channels Ba 2+ caused severe decrease in cell volume and blocked the activation. In general, the obtained data demonstrates that the initiation of pollen germination both in vivo and in vitro involves the activation of K + and Cl -release. An important role in these processes is played by NPPB , TEA and Ba 2+ sensitive plasmalemma ion channels.

Structure of Anther Epidermis and Endothecium, Production of Pollen, and Content of Selected Nutrients in Pollen Grains from Six Rubus idaeus L. Cultivars

“…Potassium and chlorine channels play a crucial role in all aspects of osmolarity and are responsible for numerous other functions in plants, including sexual reproduction. Activation of K + and Cl − release with the contribution of NPPB ((5-nitro-2-(3-phenylpropylamino) benzoic acid), TEA (tetraethylammonium chloride), and Ba 2+ -sensitive plasmalemma ion channels has key importance for the initiation of pollen germination and regulation of pollen tube growth via regulation of turgor pressure, membrane potential, and water uptake in the pollen tube [171][172][173].…”

Tip‐localized Ca2+‐permeable channels control pollen tube growth via kinase‐dependent R‐ and S‐type anion channel regulation

“…On the one hand, uptake of anions into the PTs serves the fast osmotically driven growth process; on the other hand, tip efflux of anions strongly correlates with PT growth rate (Zonia et al, 2001(Zonia et al, , 2002Gutermuth et al, 2013). Leakage of anions from pollen grains is essential to initiate pollen germination, while tube growth is inhibited when anion fluxes are disrupted pharmacologically (Zonia et al, 2002;Breygina et al, 2009Breygina et al, , 2010Breygina et al, , 2012Gutermuth et al, 2013). Apical anion fluxes are two to three orders of magnitude greater than the ones for Ca 2+ and H + , suggesting that they likely play an important physiological role in PT growth control as well (Holdaway-Clarke et al, 1997;Certal et al, 2008).…”

Dynamics of Pollen Activation and the Role of H+-ATPase in Pollen Germination in Blue Spruce (Picea pungens)

“…Plants 2020, 9, 1760 2 of 12 The transition of a vegetative cell from dormant state to active metabolism (called activation) has been studied mainly in angiosperms. In tobacco, lily, corn and Arabidopsis pollen, several events preceding the onset of polar growth have been described as follows: cytoplasm alkalinization and activation of respiration [14][15][16], efflux of K + and Cl − [17], influx of Ca 2+ in the aperture area [18], plasma membrane hyperpolarization [19], starch synthesis [20], protein synthesis from mRNA accumulated before anthesis [21]. All these events take place during the first 10-30 min of germination in vitro.…”