Effects of proteins, oxidants and antioxidants on germination of plant microspores

The compounds present in pollen excretions (which participates in allelopathy), have been analyzed in model systems of generative microspores (pollen) from Hippeastrum hybridum and vegetative microspores of horsetail (Equisetum arvense). These compounds were proteins and substances related to reactive oxygen species (oxidants and antioxidants) found in pollens and vegetative microspores. Both types of microspores contained high-molecular (< 2000 kDa and subunits with SDS near 90–94 kDa) and low-molecular (< 30 kDa) proteins having cholinesterase, peroxidase and superoxide dismutase activity. The effects of pollen proteins (monoamine oxidase, peroxidase, hexokinase, α-amylase, pepsin, trypsin, cytochrome C, ferritin, haemoglobin, cholinesterase and lysozyme) were tested on microspores development. Among the proteins, cytochrome C, ferritin, haemoglobin, subtilisin and trypsin strongly inhibited the pollen germination, whereas, the inhibition in vegetative microspores was observed with pepsin and amylase. The other analyzed peptides either weakly stimulated or had no effect on spore's germination. Reactive oxygen species (peroxides or superoxide) formed anion radical from the catecholamines [(dopamine and noradrenaline), transamine and iprazide (inhibitors of monoamine oxidases)], stimulated the germination (20–100% increase) of both spore types. While antioxidants (dithionite,mannitol, ascorbate, peroxidase, superoxide dismutase, ecdysone, caffeic and chlorogenic acids, austricine, gaillardine and grosshemine) inhibited the germination. However, high concentration of ozone (0.2 μl/L) inhibited the reaction and damaged the cells. Therefore role of reactive oxygen species for growth enhancement and antioxidants retardation may be important in pollen-pollen and pollen-pistil interactions. Possible mechanisms of cell-cell interactions with identified compounds have been discussed.