Cuscuta
Cuscuta (/kʌsˈkjuːtə/), commonly known as dodder or amarbel, is a genus of over 201 species of yellow, orange, or red (rarely green) parasitic plants. Formerly treated as the only genus in the family Cuscutaceae, it now is accepted as belonging in the morning glory family, Convolvulaceae, on the basis of the work of the Angiosperm Phylogeny Group.[1] The genus is found throughout the temperate and tropical regions of the world, with the greatest species diversity in subtropical and tropical regions; the genus becomes rare in cool temperate climates, with only four species native to northern Europe.[2]
Folk names include: strangle tare, scaldweed, beggarweed,[3] lady's laces, fireweed,[4] wizard's net, devil's guts, devil's hair, devil's ringlet, goldthread, hailweed, hairweed, hellbine, love vine, pull-down, strangleweed, angel hair, and witch's hair.[5]
Cuscuta can be identified by its thin stems appearing leafless, with the leaves reduced to minute scales. In these respects it closely resembles the similarly parasitic, but unrelated genus, Cassytha. From mid-summer to early autumn, the vines can produce small fruit that take the same color as the vine, and are approximately the size of a common pea. It has very low levels of chlorophyll; some species such as Cuscuta reflexa can photosynthesize slightly, while others such as C. europaea are entirely dependent on the host plants for nutrition.[6]
Dodder flowers range in color from white to pink to yellow to cream. Some flower in the early summer, others later, depending on the species. The seeds are minute and produced in large quantities. They have a hard coating, and typically can survive in the soil for 5–10 years, sometimes longer.
Dodder seeds sprout at or near the surface of the soil. Although dodder germination can occur without a host, it has to reach a green plant quickly and is adapted to grow towards the nearby plants by following chemosensory clues.[5] If a plant is not reached within 5 to 10 days of germination, the dodder seedling will die. Before a host plant is reached, the dodder, as other plants, relies on food reserves in the embryo; the cotyledons, though present, are vestigial.[7]
After a dodder attaches itself to a plant, it wraps itself around it. If the host contains food beneficial to dodder, the dodder produces haustoria that insert themselves into the vascular system of the host. The vestigial root of the dodder in the soil then dies. The dodder can grow and attach itself to multiple plants. In tropical areas, it can grow more or less continuously and may reach high into the canopy of shrubs and trees; in cold temperate regions, it is an annual plant and is restricted to relatively low vegetation that can be reached by new seedlings each spring.
1). Cuscuta plant
2). Host plant
3). Cuscuta leaves
4). Ground tissue
5). Phloem
6). Sugars and nutrients
7). Epidermal tissue
8). A Cuscuta haustorium growing into the phloem of the host plant.