In contrast to the behaviour of Afro-alpine plants, Andean Espeletias are injured by freezing of the cell water. Obviously ice formation is occurring intracellularly in these plants. They need to avoid freezing of cellular water and survive the nights in a super-cooled state. As depicted in Fig. 12.15 for all the different organs and tissues of Espeletia spicata and E. timotensis in the Andes, the supercooling points, at which ice formation would happen, are always much lower than the lowest temperatures actually found in these organs and tissues. Ambient temperature is modulated in the tissues by the various strategies discussed in Sect. 12.3.1. Supercooling and freezing avoidance for the Andean giant-rosette plants therefore must be considered as an appropriate mode of achieving sufficient frost resistance.
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.