Effect of UV-B stress on olive (Olea europaea L.) pollen tubes: A study of callose plug deposition and male germ unit integrity

While UV-B radiation is beneficial to plant growth, it can also cause adverse effects. The pollen tube, a key component of plant reproduction with a tip growth mechanism, is an excellent cellular model for understanding how environmental stressors such as UV-B radiation affect plant cell growth. This research investigated the effect of UV-B on olive pollen both before and after germination. Pollen grains were hydrated and exposed to UV-B radiation for 1 h. Pollen tube germination was then evaluated 4 and 24 h after exposure. To study the effect of UV-B radiation on developing pollen tubes, pollen was germinated for 4 h prior to 1 h of UV-B exposure. Pollen tube growth was evaluated by assessing the distribution of cell wall components, the distance between callose plugs and nuclei, and the distance between the male germ unit and the pollen tube tip. We also examined the accumulation of callose synthase. The results showed that UV-B radiation significantly inhibited the growth of pollen tubes, thereby preventing successful fertilization. The effect of UV-B exposure on pollen tube growth was mainly due to the alteration of position of callose plugs and the level of callose synthase in the pollen tube, potentially affecting its growth. In addition, UV-B radiation affected the movement and integrity of the male germ unit, a critical element for successful fertilization. This research sheds light on how UV-B radiation affects the growth of pollen tubes and highlights the need for further research into the effects of UV-B radiation on plant cells and plant reproduction.