This week I’m going to talk about how plants can survive in cold environments. The two biomes where cold is the main restrictive factor of the plant growth are tundra and alpine. In these places, the temperature can be under 0⁰C. Therefore, how do plants do to survive there?

INTRODUCTION

The cold is a restrictive factor to plant growth. It can be caused for two main reasons: height and high latitudes. When the height raises, the cold also does it; for each 100 meters of height, temperature gets down 1ºC. And in high latitudes, cold is caused by low insolation (only a little amount of sun’s heat is received). Plants can live until certain limits in high mountains, originating the alpine biome, and even become an ecosystem above the polar circle in the northern hemisphere, forming the tundra biome. Therefore, plants can survive in these cold ecosystems somehow. But, what kind of plants are and how do they do it?

On the left, tundra zone; and on the right, alpine zone (Image by Terpsichores).

VEGETATION STRUCTURE

First of all, we need to know what kind of plants are living in these places.

The trees’ growth is very restricted in both biomes. Indeed, trees are missing in tundra and only can be found in subalpine zone in the high mountains, between 1.600m and 2.400m; even so, the biggest height where trees can occur depends of different climatic factors and of the topographic relief. Once there are no trees, so there is no forest, we talk about alpine zone in high mountains.

Trees on subalpine zone (Photo taken by Jo Simon on Flickr).

On the other hand, shrubs are uncommon in both biomes, being the most of them smaller and creeping. That way, they can protect themselves against heavy frosts and cold winds, because they get covered of snow during the unfavourable period. Cranberry bush (Vaccinium vitis-idaea) is a good example of this kind of shrubs.

Cranberry bush (Vaccinium vitis-idaea) (Photo taken by Arnstein Rønning).

The herbs, bryophytes (e.g. mosses) and lichen together, are the most dominant of these two biomes, because they are the most abundant.

On the left, tundra in Siberia (Photo taken by Dr. Andreas Hugentobler); on the right, alpine zone in Monte Blanco (Photo taken by Gnomefillier)

PLANT ADAPTATIONS

Due to cold weather and other restrictive factors of these biomes, plants have had to adapt in different ways. In these two biomes, the summer is the favourable season and is when plants can develop themselves. But in winter, unfavourable period, they can only remain dormant in the form of seeds or reducing their activity to a minimum, thus avoiding own energy consumption.

For all these, these plants produce storage organs below ground, where they are protected from cold temperatures. Examples are rhizomes (underground stems, usually elongated and with horizontal growth, root-like) and bulbs (short and thick stem, covered with more or less developed fleshy leaves). These bodies ensure sufficient energy reserves during the unfavourable period. Furthermore, their roots are thick and can also accumulate reserves.

On the left, iris  rhizome (Iris) (Photo taken by David Monniaux); On the right, lily bulb (Lilium) (Photo taken by Denis Barthel).

On the other hand, their capacity to reach new zones to live, new habitats, depends more of the vegetative reproduction or asexual reproduction, that is, the emission of buds, underground organs, etc. And, in particularly, it is favoured by a high number of buds (plant organ that, when is developed, forms a stem, branch or flower).

Bud (Photo taken by Sten Porse).

A very curious adaptation, that can also protects against the wind, is that some plants are cushion-shaped. This morphology allows moisture and temperature to increase within the plant, and therefore stimulates the development and facilitates photosynthesis.

Cushion-shaped plant (Minuartia arcica) (Photo taken by Σ64).

Knowing that the favourable season is brief, plants usually are evergreen, that is, they have leaves during all year; and, that way, they don’t use energy to regenerate new leaves. Also, plant cells don’t freeze because they produce high concentrations of monosaccharides (simple sugars). So, it makes very difficult to freeze the perennial parts (those living all year).

Lucile's Glory-of-the-snow (Chionodoxa luciliae) (Photo taken by Ruhrfisch).

Moreover, their life cycle is also affected. The favourable period is so brief that it is often impossible to grow, forming flowers and fruits in the same year. Therefore, the plants usually live longer than a year and tend to perform only one of these three functions during the favourable season. Then remain dormant during unfavourable weather. So, its cycle is affected and it’s very impossible to live there to annual plants

Thanks to all these adaptations, plants have managed to live in such extraordinary places like these biomes, as incredible survivors. Remember, if you liked this article, you should not forget to share it. Thank you very much for your interest.

REFERENCES

• Notes of Botany, Phanerogamae, Science of the biosphere and Analysis of vegetation, Degree of Environmental Biology, UAB.
• Enciclopedia Catalana 1993-98. Biosfera. Volums. 9 Tundra i insularitat V. Krvazhimskii; A. N. Danilov. 2000. Reindeer in tundra ecosystems: the challenges of understanding System complexity. Publicat a tundra ecosystems: the challenges of understanding system complexity, V. 19, 107-110 pp.
• Walter H. 1998 Vegetació i zones climàtiques del món. L’estructuració ecològica de la geobiosfera. 2ªed cat. Promocions i Publ Univ SA, Barcelona
• http://161.116.68.143/website/geoveg/docs/Carrillo_06.pdf
• http://www.apicat.com/web/apiflora_1b.htm

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