| Abstract: | - Boron (B) is essential for normal plant growth, including pollen tube growth. B deficiency influences various physiological and metabolic processes in plants. However, the underlying mechanism of B deficiency in pollen tube growth is not sufficiently understood. In the present research, the influence of B deficiency on apple (Malus domestica) pollen tube growth was studied and the possible regulatory mechanism evaluated.
- Apple pollen grains were cultured under different concentrations of B. Scanning ion‐selective electrode technique, fluorescence labelling and Fourier‐transform infrared (FTIR) analysis were used to detect calcium ion flux, cytosolic Ca2+ concentration (Ca2+]cyt), actin filaments and cell wall components of pollen tubes.
- B deficiency inhibited apple pollen germination and induced retardation of tube growth. B deficiency increased extracellular Ca2+ influx and thus led to increased Ca2+]cyt in the pollen tube tip. In addition, B deficiency modified actin filament arrangement at the pollen tube apex. B deficiency also altered the deposition of pollen tube wall components. Clear differences were not observed in the distribution patterns of cellulose and callose between control and B deficiency treated pollen tubes. However, B deficiency affected distribution patterns of pectin and arabinogalactan proteins (AGP). Clear ring‐like signals of pectins and AGP on control pollen tubes varied according to B deficiency. B deficiency further decreased acid pectins, esterified pectins and AGP content at the tip of the pollen tube, which were supported by changes in chemical composition of the tube walls.
- B appears to have an active role in pollen tube growth by affecting Ca2+]cyt, actin filament assembly and pectin and AGP deposition in the pollen tube. These findings provide valuable information that enhances our current understanding of the mechanism regulating pollen tube growth.
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