Ni2+ effects on Nicotiana tabacum L. pollen germination and pollen tube growth

Abstract

To investigate the mechanisms of Ni(2+) effects on initiation and maintenance of polar cell growth, we used a well-studied model system-germination of angiosperm pollen grains. In liquid medium tobacco pollen grain forms a long tube, where the growth is restricted to the very tip. Ni(2+) did not prevent the formation of pollen tube initials, but inhibited their subsequent growth with IC(50) = 550 μM. 1 mM Ni(2+) completely blocked the polar growth, but all pollen grains remained viable, their respiration was slightly affected and ROS production did not increase. Addition of Ni(2+) after the onset of germination had a bidirectional effect on the tubes development: there was a considerable amount of extra-long tubes, which appeared to be rapidly growing, but the growth of many tubes was impaired. Studying the localization of possible targets of Ni(2+) influence, we found that they may occur both in the wall and in the cytoplasm, as confirmed by specific staining. Ni(2+) disturbed the segregation of transport vesicles in the tips of these tubes and significantly reduced the relative content of calcium in the aperture area of pollen grains, as measured by X-ray microanalysis. These factors are considered being critical for normal polar cell growth. Ni(2+) also causes the deposition of callose in the tips of the tube initials and the pollen tubes that had stopped their growth. We can assume that Ni(2+)-induced disruption of calcium homeostasis can lead to vesicle traffic impairment and abnormal callose deposition and, consequently, block the polar growth.

Male Fertility under Environmental Stress: Do Polyamines Act as Pollen Tube Growth Protectants?

“…A dose-effect linearity was also found for apricot and cherry pollen [56]. Nickel shows combined effects, as it does not block germination but prevents pollen tube growth [57]. Lead treatment causes profound alterations in pollen tubes, which show cessation of growth and uneven distribution of cell wall components, most likely by targeting the cytoskeleton [58].…”

Geological Substrate Effects on Teucrium montanum L. (Lamiaceae) Morphological Traits: Geometric Morphometrics Approach

“…Previous studies confirmed the direct effect of serpentinite soils on inflorescence size and height, in response to the lower amount of nutrients in the substrate [ 67 ]. The presence of heavy metals such as Ni in the substrate has a negative effect on plant reproduction [ 68 ]. In plants, the evolutionary response to environmental stress is slow growth, and consequently low nutrient requirements, with the drawback of lower overall productivity.…”

A first test of elemental allelopathy via heterospecific pollen receipt

“…We should note, however, that Ni may be complexed to organic molecules (Homer et al, 1991; Leitenmaier and Küpper, 2013), so the actual Ni exposure from germinated S. polygaloides pollen may be less than estimated. Nonetheless, there are reports in the literature for both inhibitory (e.g., Nicotiana tabacum L.; Tuna et al, 2002; Breygina et al, 2012) and stimulatory effects of Ni +2 ions or other heavy metals (e.g., Cd, and Fe) on pollen germination and tube growth Sawidis and Reiss, 1995; Xiong and Peng, 2001; Tuna et al, 2002). So it is possible that greater pollen germination by M. guttatus in response to S. polygaloides pollen receipt in our study reflects stimulation by Ni or through its effects on metabolism (Welch, 1981).…”

“…While metal accumulators are often adapted to soils with high concentrations of heavy metals, these metals not only negatively affect the growth of intolerant species but can also cause abnormalities in their gamete and embryo development (Sabrine et al, 2010; Mohsenzadeh et al, 2011). Moreover, direct exposure to some heavy metal ions (e.g., Ni) can inhibit pollen germination and pollen tube growth, leading to decreased seed production (Malan and Farrant, 1998; Tuna et al, 2002; Breygina et al, 2012). As recent work has shown that Ni can accumulate in pollen of hyperaccumulators (Meindl et al, 2014; Sánchez‐Mata et al, 2014), Ni may be introduced to heterospecific pistils via interspecific pollen transfer.…”