Do exophytic microorganisms affect in vitro pollen germination and pollen tube growth in Camellia sinensis?

Since tea is an economically valuable medicinal plant, pollen germination and pollen tube elongation are important for seed yield and quality. Therefore, strategies to increase pollen tube elongation for tea production are developing and especially the use of beneficial microorganisms is gaining importance. We aimed to investigate the potential activities of Streptomyces albidoflavus, Streptomyces indigoferus, Streptomyces nanhaiensis, Pseudomonas fluorescens, Paenibacillus xylanilyticus, and Paenibacillus alginolyticus on pollen germination and pollen tube length of Camellia sinensis. The amount of reducing sugars was determined by DNS method, and heat map analyses were performed to evaluate pollen germination, pollen tube length, and RS content. The tested bacteria were grown on pollen germination medium for 3, 6, and 24 h, after which the aforementioned parameters were analyzed. No statistically significant effect of treatments with tested bacteria was found in terms of pollen germination. However, especially in pollen samples treated with P. alginolyticus at 6 and 24 h, pollen tube length was found to be the most effective with an increase of 28.6 and 13.87%. Reducing sugar content was found to be the highest in S. indigoferus + pollen and P. alginolyticus + pollen groups at 24 h. According to heat map analyses, P. alginolyticus maintained consistently high values for pollen germination, tube elongation, RS content and showed the strongest positive effect. In conclusion, P. alginolyticus significantly increased pollen tube elongation and RS levels, suggesting its potential role in plant development and pollination. These findings indicate that such rhizosphere bacteria may act as biostimulants to enhance fertilization and support sustainable tea cultivation.