Alpine plants are plants that grow in the alpine climate, which occurs at high elevation and above the tree line. Alpine plants grow together as a plant community in alpine tundra. Alpine plants are not a single taxon. Rather, many different plant species live in the alpine environment. These include perennial grasses, sedges, forbs, cushion plants, mosses, and lichens. Alpine plants must adapt to the harsh conditions of the alpine environment, which include low temperatures, dryness, ultraviolet radiation, and a short growing season.
Some alpine plants serve as medicinal plants.
Surviving low temperature extremes 
Most alpine plants are faced with low temperature extremes at some point in their lives. There are a number of ways that a plant can survive these extremes. Plants can avoid exposure to low temperature by using different forms of seasonal phenology, morphology, or by variable growth form preference. They can also avoid the freezing of their exposed tissues by increasing the amount of solutes in their tissues, known as freezing-point depression. Another, somewhat similar, method plants may use to avoid freezing is supercooling, which prevents ice crystallization within plant tissues. These methods are only sufficient when temperature is only moderately cold. In the alpine zone, temperatures are often low enough that these methods are not sufficient. When plants need a more permanent solution, they can develop freeze tolerance. Plants can also dehydrate their cells by moving water into intercellular spaces. This causes ice formation outside of the cell where ice crystals will not cause damage. When all of these strategies fail to prevent frost damage, alpine plants often have the capacity to repair or replace the organs damaged. As it is often difficult to prevent damage, many alpine plants depend on the replacement of their organs. They help make this possible by placing their meristems below ground, where temperatures are generally warmer.
Avoidance of desiccation 
In alpine areas, water availability is often variable. Bryophytes and lichens exhibit high desiccation tolerance, which contributes to their abundance throughout all alpine areas habitats. Among higher plants, tissue desiccation is rare at high altitudes. If it does occur, it normally happens to plants growing on exposed sites, where wind stress is increased. Alpine plants avoid water loss by deep rooting and increased stomatal control. Plants at low elevation normally reach maximum stomatal opening in the morning while alpine plants reach maximum opening mid-day, when temperature is greatest. Alpine succulent plants often utilize CAM photosynthesis to avoid water loss.
Avoidance of ultraviolet radiation 
Because ultraviolet radiation tends to increase with elevation, it is often assumed to be a stress factor among alpine plants. In the past, there have been many attempts to research how ultraviolet radiation may influence alpine plant forms. However, it is uncertain if the growth and development of plants is affected by ultraviolet radiation. It is also not clear if the radiation is responsible for promoting genetic differentiation, leading to stunted growth forms.
Alpine plants use both sexual reproduction and asexual reproduction. Sexual reproduction has limits in high alpine areas, especially in areas with a short growing seasonin alpine zones at high latitudes. In tropical alpine zones with a year round growing season, such as the northern Andes, plants can flower year round. Regardless of when alpine plants flower, pollinators are often scarce. The activity of pollinators decreases with increasing altitude. The most common pollinators in the alpine zone are bumblebees and flies. Plants utilize different strategies to deal with these limits, including alternate flowering time and clonal propagation.
Early flowering plants 
Some plants flower immediately after snow melting or soil thawing. These early flowering plants always form their flowers in the previous season, called preformation. Consequently, they risk frost damage to the preformed inflorescence. In order to minimize frost damage, preformed flowers are often surrounded by tightly packed bracts that are densely covered in trichomes. This helps to keep the interior of a flower bud warm. Because of early season pollinator limitation, plants that bloom early generally have a low rate of reproductive success. One advantage of flowering early is that seeds that are produced have a greater chance of developing to maturity before the next freeze. They also have a high outcrossing rate, which helps to increase genetic diversity.
Mid-season flowering 
Approximately half of all alpine species flower in mid-season. Flowering at the seasonal peak combines some of the advantages and risks of early flowering and late flowering plants. Some mid-season plants pre-form of their inflorescences, but not all do.
Late flowering 
Late flowering occurs after the main growing season ends. They have a high seed output but their seeds have a reduced rate of maturing because of time constraints. These plants tend towards self pollination, apomixis, and vivipary.
Clonal progagation 
Because investment in flowers and seed production can be costly for alpine plants, they often use clonal propagation. This strategy becomes increasingly more frequent as altitude increases, and is most common among cryptogams and grasses. Some alpine plants use it as their predominant method of reproduction. In these plants, sexual reproduction is rare and does not contribute significantly to reproductive output. An example of such a plant is Carex curvula, which is estimated to have a clonal age of approximately 2000 years.
Medicinal alpine plants 
There are a number of alpine plants that are used economically. In the Himalayas, hundreds of species are traded for medicinal and aromatic uses. It is estimated that the annual trade of these plants amounts to millions of US dollars. Many households in rural Nepal and India rely on medicinal alpine plant trade as a source of income. This creates an increased need to focus on plant conservation in these areas, ensuring sustainable harvest as well as ecosystem sustainability. Some of the species harvested in Nepal include Neopicrorhiza scrophulariiflora, Nardostachys grandiflora, Aconitum spicatum, Dioscorea deltoidea, Aconitum heterophyllum, Rheum australe, Bergenia, and Epimerantha macraei. In the Indian Himalayas, the alpine medicinal plants such as Dactylorhiza hatagirea, Picrorhiza kurrooa, Aconitum heterophyllum, Fritillaria roylei, Podophyllum hexandrum are under severe pressure due to over-exploitation for commercial purposes.
See also 
- Austrheim, Gunnar; Kristian Hassel; Atle Mysterud (2005). "The Role of Life History Traits for Bryophyte Community Patterns in Two Contrasting Alpine Regions". The Bryologist 108 (2): 259–271. doi:10.1639/0007-2745(2005)108[0259:TROLHT]2.0.CO;2.
- Hacker, Jürgen; Gilbert Neuner (2008). "Ice Propagation in Dehardened Alpine Plant Species Studied by Infrared Differential Thermal Analysis (IDTA)". Arctic, Antarctic, and Alpine Research 40 (4): 660–670. doi:10.1657/1523-0430(07-077)[HACKER]2.0.CO;2.
- Kala, Chandra Prakash (2000). "Status and conservation of rare and endangered medicinal plants in the Indian trans-Himalaya". Biological Conservation 93 (3): 371–379. doi:10.1016/S0006-3207(99)00128-7.
- Kala, Chandra Prakash (2005). "Health traditions of Buddhist community and role of amchis in trans-Himalayan region of India". Current Science 89 (8): 1331–1338.
- Körner, Christian (2003). Alpine Plant Life: Functional Plant Ecology of High Mountain Ecosystems. Berlin: Springer.
- Smith Olsen, Carsten; Overgaard Larsen, Helle (2003). "Alpine medicinal plant trade and Himalayan mountain livelihood strategies". The Geographical Journal 169 (3): 243–254. doi:10.1111/1475-4959.00088.
- Steinger, Thomas; Christian Körner; Bernhard Schmid (1996). "Long-term persistence in a changing climate: DNA analysis suggests very old ages of clones of alpine Carex curvula". Oecologia 105 (1): 94–99. doi:10.1007/BF00328796.
- Tsukaya, H.; T. Tsuge (2001). "Morphological Adaptation of Inflorescences in Plants that Develop at Low Temperatures in Early Spring: The Convergent Evolution of "Downy Plants"". Plant Biology 3 (5): 536–543. doi:10.1055/s-2001-17727.
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