What is a Sundew?
 Drosera oblanceolata (Sunset Peak, HK)  Drosera madagascariensis  Drosera sp. "South Africa"  Drosera 'Lake Badgerup', a pygmy sundew  Basic leaf anatomy of a Drosera capensis leaf. The tentacles, leaf blade (lamina) and petiole are labeled. The base of the leaf would be below the petiole and the stipule is located at the end of the leaf base, and it connects the leaf to the stem). | General description (scientific description is below) Sundews are carnivorous plants. This means that they trap and digest insects to obtain extra nutrients, such as nitrogen. This allows sundews to live where other plants cant- in nutrient-depleted soils. Some sundews can obtain a sufficient amount of nutrients from the soil. which allows them to go for long periods of time without catching food, and survive. Some sundews (such as Drosera glanduligera) are not very efficient at absorbing nutrients through their roots, so they rely more heavily on catching prey. This means that if they do not catch prey after germination, they will only live a short time. A fun fact is that "European sundew sepcies have been used in folk medicine since the Middle Ages, as remedies for coughs and respiratory ailements" (94). Depending on where you look (ie old books or Wikipedia), there are from 86-188 distinguished sundew species. Since there are so many species, hybrids readily occur in nature, and many sundew growers have made their own unique hybrids. The leaves of sundews are covered with "tentacles". The tip of every tentacle contains a nectar gland, which produces a globule of a sticky digestive enzyme. When an insect lands on the leaf, they get stuck on the dew. As they struggle to get out of the dew, the tentacles/leaf start(s) to wrap around the insect (through a complicated biological process involving several action potentials). The dew eventually suffocates the insect, and it stops moving. The digestive enzymes absorb nutrients that the sundew needs. If sundews are fed (or capture their own food), they will generally grow larger and faster than plants that are not being fed. Sundews can be found all over the world. Because of this, there is much diversity in the genus Drosera. Sundews are divided into several categories by type and location: Fork-leaved, Temperate, Tuberous, Pygmy (very tiny), Annual, South Aftrican, South American, Petiolaris (Australia), and Queensland sundews. A specific example of diversity in the genus Drosera can be seen in comparing Temperate and Petiolaris sundews. Temperate sundews prefer cooler to moderate temperatures, and grow well in low to medium humidity. Petiolaris sundews thrive only if given hot temperatures and very high humidity. While most sundews are very small (some smaller than a dime) "there are also climbing plants that reach a lenght up to 3 m". This shows how diverse Drosera are. Sundews are able to survive through hot dry seasons or cold seasons "with the aid of perennating buds, storage roots, or tubers" (97). Taxonomy (Scientific Name of the Sundew) Sundews belong to the genus Drosera. The family of carnivorous plants that they belong to is Droseracae. As far as the origin of the name Drosera goes, according to James Pietropaolo's Carnivorous Plants of the World, the name "Drosera is derived from the Greek words "droseros" which means dewy and 'drosos' meaning dew, alluding to the resemblance of the drop of mucilage on the tentacle gland to dew" (75). Scientific/ Biological Description "Most Drosera species are perennial herbs; a few species are annual herbs or dwarf shrub" (97). The structure of the Drosera leaf corresponds to that of a normal foliage leaf and consists of a base, a stalk (petiole), and a blade (lamina). "The petiole connects the leaf base with the lamina, which is covered with tentacles (100). "Sundews have active adhesive traps, with the trapping device consisting of the leaves and their tentacles and sessile glands. The stalks of the tentacles consist of an outer cell layer (epidermis), a few cell layers lying beneath it, and a central string of tracheids that conduct water" (104) The leaf base generally bears a membranous, papery-thin appendage (median stipule) on the upperside that can be regarded as a product of fused stipules" (99). This trait is not found in any tuberous sundews. Median stipules are important for rosetted sundew species because it is responsible for allowing the sundew to form perreniate buds. "This
bud helps the species of temperate and cold climates to overwinter and
the species of subtropical climates to survive through tho the next
rainy season. The median stipules, which develop long before the rest
of the leaf, lie close together , and the space between them is filled
with air. Due to the inclusion of this air, the bud often appears white
and reflects sunlight well, while water is virtually unable to
penetrate into the bud (99). | ||||||
Works Cited
Barthlott, Wilhelm et.al. The Curious World of Carnivorous Plants. Portland: Timber Press, 2007.
Additional Questions or Suggestions?
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