Summary• The role of heterotrimeric G proteins in pollen germination and tube growth was investigated using Arabidopsis thaliana plants in which the gene ( GPA ) encoding the G-protein α subunit (G α ) was null or overexpressed.• Pollen germination, free cytosolic calcium concentration ([Ca 2 + ] cyt ) and Ca 2 + channel activity in the plasma membrane (PM) of pollen cells were investigated.• Results showed that, compared with pollen grains of the wild type (ecotype Wassilewskija, ws), in vitro germinated pollen of G α null mutants ( gpa1-1 and gpa1-2 ) had lower germination percentages and shorter pollen tubes, while pollen from G α overexpression lines (wG α and cG α ) had higher germination percentages and longer pollen tubes. Compared with ws pollen cells, [Ca 2 + ] cyt was lower in gpa1-1 and gpa1-2 and higher in wG α and cG α . In whole-cell patch clamp recordings, a hyperpolarization-activated Ca 2 + -permeable conductance was identified in the PM of pollen protoplasts. The conductance was suppressed by trivalent cations but insensitive to organic blockers; its permeability to divalent cations was Ba 2 + > Ca 2 + > Mg 2 + > Sr 2 + > Mn 2 + . The activity of the Ca 2 + -permeable channel conductance was down-regulated in pollen protoplasts of gpa1-1 and gpa1-2 , and up-regulated in wG α and cG α .• The results suggest that G α may participate in pollen germination through modulation of the hyperpolarization-activated Ca 2 + channel in the PM of pollen cells.

Extracellular ATP (eATP) plays an essential role in plant growth, development, and stress tolerance. Here, we report that eATP participated in Nicotiana tabacum pollen germination (PG) and pollen tube growth (PTG) by regulating K and Ca influx. Exogenous ATP or ADP effectively promoted PG and PTG in a dose-dependent manner; weakly hydrolysable ATP analog (ATPγS) showed a similar effect. AMP, adenosine, adenine, and phosphate did not affect PG or PTG. Within a certain range, higher concentrations of K or Ca in the medium increased the effect of ATP in promoting PG and PTG. However, in mediums containing K or Ca concentrations above this range, the effect of ATP was reversed, resulting in PG and PTG inhibition. Ca chelators (EGTA), Ca channel blockers, and K channel blockers suppressed ATP-promoted PG and PTG. Results from a patch clamp showed that ATP activated a K and Ca influx in pollen protoplasts. These results suggest that, as an apoplastic signal, eATP may be involved in PG and PTG via regulating Ca and K absorption.

As an apoplastic signal, extracellular ATP (eATP) is involved in plant growth and development. eATP promotes tobacco pollen germination (PG) and pollen tube growth (PTG) by stimulating Ca2+ or K+ absorption. Nevertheless, the mechanisms underlying eATP-stimulated ion uptake and their role in PG and PTG are still unclear. Here, ATP addition was found to modulate PG and PTG in 34 plant species and showed a promoting effect in most of these species. Furthermore, by using Arabidopsis thaliana as a model, the role of several signaling components involved in eATP-promoted ion (Ca2+, K+) uptake, PG, and PTG were investigated. ATP stimulated while apyrase inhibited PG and PTG. Patch-clamping results showed that ATP promoted K+ and Ca2+ influx into pollen protoplasts. In loss-of-function mutants of P2K1 (dorn1-1 and dorn1-3), heterotrimeric G protein α subunit (gpa1-1, gpa1-2), or cyclic nucleotide gated ion channel (cngc2, cngc4), eATP-stimulated PG, PTG, and ion influx were all impaired. Our results suggest that these signaling components may be involved in eATP-promoted PG and PTG by regulating Ca2+ or K+ influx in Arabidopsis pollen grains.

Fitting mathematical models to describe the influence of topographic factors and coexisting plants on wild jujube distribution was performed to provide a scientific basis for wild jujube forestation. Investigation quadrats, with straight-line distances between adjacent quadrats of longer than 100 m, were set up in areas of wilderness or low human disturbance, which were rich in wild plant species. Data concerning altitude, slope aspect, slope position and slope degree of each investigation quadrat, as well as the type and number of coexisting wild plants, were collected. Based on this, correlations with the average number, occurrence probability and density of wild jujube and these variables were analyzed, and data models were established. Results of analyses show that topographic factors such as altitude, aspect, gradient, slope and position, play an important role in the distribution of wild jujube; and that Vitex negundo var. heterophylla (Franch.) Rehd. coexistence is related to wild jujube distribution. Both average number and occurrence probability of wild jujube conform to a GaussAmp model with altitude. The highest average number was recorded at 581.24 ± 13.78 m above sea level, and the highest occurrence probability at 462.53 ± 36.67 m above sea level. Average number and occurrence probability of wild jujube were fit to a linear model with slope aspect—with mathematical slope 0.49 ± 0.16—indicating that wild jujube is a light-loving and drought-tolerant plant. Average number and density of wild jujubes were fit to GaussAmp models with slope position. The highest average number and the highest density of wild jujube appears on the upper part of the middle slope. Wild jujube occurrence probability was correlated to slope degree in a quadratic equation model. With an increase in slope degree, the distribution number of wild jujube increased sharply. The survey data of slope position and slope degree further reinforced the observed drought-resistance qualities of wild jujube. Average number and density of wild jujubes were correlated to the number of Vitex negundo var. heterophylla by quadratic equation models. No other plants investigated conformed to a statistically significant relationship with wild jujube distribution. Our results suggest altitude, slope aspect, slope position and slope degree play an important role in wild jujube distribution, and that Vitex negundo var. heterophylla is an important coexistent plant species for wild jujube.