Wagner Johanna, Gastl Evelyn, Kogler Martin, Scheiber Michaela
Institute of Botany, Faculty of Biology, University of Innsbruck, Sternwartestrasse 15, 6020 Innsbruck, Austria.
Plants (Basel). 2016 Dec 29;6(1):2. doi: 10.3390/plants6010002.
In temperate climates, most plants flower during the warmer season of the year to avoid negative effects of low temperatures on reproduction. Nevertheless, few species bloom in midwinter and early spring despite severe and frequent frosts at that time. This raises the question of adaption of sensible progamic processes such as pollen germination and pollen tube growth to low temperatures. The performance of the male gametophyte of 12 herbaceous lowland species flowering in different seasons was examined in vitro at different test temperatures using an easy to handle testing system. Additionally, the capacity to recover after the exposure to cold was checked. We found a clear relationship between cold tolerance of the activated male gametophyte and the flowering time. In most summer-flowering species, pollen germination stopped between 1 and 5 °C, whereas pollen of winter and early spring flowering species germinated even at temperatures below zero. Furthermore, germinating pollen was exceptionally frost tolerant in cold adapted plants, but suffered irreversible damage already from mild sub-zero temperatures in summer-flowering species. In conclusion, male gametophytes show a high adaptation potential to cold which might exceed that of female tissues. For an overall assessment of temperature limits for sexual reproduction it is therefore important to consider female functions as well.
在温带气候中，大多数植物在一年中较温暖的季节开花，以避免低温对繁殖产生负面影响。然而，尽管此时严寒频发，仍有少数物种在仲冬和早春开花。这就引出了一个问题，即花粉萌发和花粉管生长等敏感的配子体形成过程如何适应低温。使用易于操作的测试系统，在不同的测试温度下，对12种在不同季节开花的草本低地物种的雄配子体表现进行了体外研究。此外，还检查了暴露于低温后恢复的能力。我们发现，活化雄配子体的耐寒性与开花时间之间存在明显的关系。在大多数夏季开花的物种中，花粉萌发在1至5摄氏度之间停止，而冬季和早春开花物种的花粉即使在零度以下的温度也能萌发。此外，在适应寒冷的植物中，正在萌发的花粉具有极强的耐霜性，但在夏季开花物种中，即使是轻微的零下温度也会使其遭受不可逆转的损害。总之，雄配子体对寒冷表现出很高的适应潜力，这可能超过雌配子体组织。因此，为了全面评估有性繁殖的温度限制，考虑雌配子体的功能也很重要。
