Overlapping Leaves Prevent Reproductive Organ from Overheating in an Alpine Plant

The alpine subnival belt (4300-5000 m a.s.l.) of Himalaya-Hengduan Mountains (HHM) experiences a summer monsoonal climate, with heavy rain fall interrupted by short periods of intense solar radiance in the growing period. Low temperature caused by rain (or cloud) slows the development of flowers and seeds; there has been an extensive interest in study how low temperature drives the evolution ofhighly-specialized morphological features in alpine plants. For example, the densely pubescent inflorescences of Saussurea medusa (known as ‘Himalayan woolly plant’) have a key role in temperature control and water repellence in cool and humid summer. On the other hand, the overlapping large semi-translucent bracts covering racemes of Rheum nobile (known as ‘Himalayan glasshouse plant’) function to warm floral tissues and have protective effects against UV-B radiation and rain. 

However, none of the research has ever focused on the selective pressure of high temperature caused by transient strong solar radiation (particularly in the midday) in alpine plant. High temperaturereduces pollen viability and some species have evolved cooling mechanisms(evaporation and self-shading) in tropical environments. In a recent study, we used Eriophyton wallichii Bentham (Lamiaceae), an alpine perennial herb with woolly structures (particularly in leaves, corolla and calyxes) and overlapping leaves covering reproductive organs, to explore the specialized morphology of an alpine plant adapted to growth and reproduce in sites characterized by transient heavy rainfall and strong solar radiation.