poikilohydry

English

Etymology

From poikilo- +‎ -hydry or a noun-forming modification of poikilohydric (see -y); compare homoiohydry.

Noun

poikilohydry (uncountable)

1. (botany) The condition of being poikilohydric; the lack of structural or functional mechanisms to actively regulate the equilibrium between the concentration of water in cell tissue and that in the environment.

   Coordinate term: homoiohydry

   Poikilohydry occurs in such organisms as lichens and bryophytes, which lack mechanisms such as waterproofing cuticles or stomata that can help resist desiccation.

   Frequently, poikilohydry is coupled with the capacity to tolerate dehydration or low water content of cell tissue and to recover from it without physiological damage.

   • 1997, S. D. Smith, R. Monson, J. E. Anderson, Physiological Ecology of North American Desert Plants, Springer, page 191:

     Nonvascular cryptogams, particularly the lichens and mosses, form a majority of the species and biomass exhibiting poikilohydry within desert regions of the world, including North America.

   • 2011, T. G. Allan Green, Leopoldo G. Sancho, Ana Pintado, Chapter 6: Ecobiology of Desiccation/Rehydration Cycles in Mosses and Lichens, Ulrich Lüttge, Erwin Beck, Dorothea Bartels (editors), Plant Desiccation Tolerance, Springer, Ecological Studies 215, page 113,

     The strategy of poikilohydry was almost certainly primitive and evolved from the production of desiccation-tolerant spores (Oliver et al. 2000). Organisms employing poikilohydry are confined to a small overall size, in particular because of the limitations to water transport that relies on capillarity (Proctor and Tuba 2002).

   • 2018, Mitchell B. Cruzan, Evolutionary Biology: A Plant Perspective, Oxford University Press, page 33:

     Their small size and ability to adhere to solid substrates allows mosses to occupy habitats where poikilohydry provides a unique advantage, but these characteristics set limits on their distribution to specific types of environments where tracheophytes are unable to dominate.

Usage notes

• Poikilohydric plants are often "desiccation tolerant", and may be studied as such. While poikilohydry does not per se imply desiccation tolerance, it does mean that the plant's "response" to dry conditions is to become desiccated—and thus that it is likely to have evolved ways to cope with that condition. In contrast, homoiohydric plants have mechanisms by which they can delay desiccation.

Translations

lack of mechanisms to establish and maintain equilibrium of water content between cells and the environment

Further reading

• Homeostasis on Wikipedia.Wikipedia
• Desiccation tolerance on Wikipedia.Wikipedia