Life cycle Mistletoe

mistletoe in winter



the mistletoe seller adrien barrère

technically, mistletoe species hemiparasites, because perform @ least little photosynthesis @ least short period of life cycle. however, academic in species contribution zero. example, species, such viscum minimum, parasitize succulents, commonly species of cactaceae or euphorbiaceae, grow largely within host plant, hardly more flower , fruit emerging. once have germinated , attached circulatory system of host, photosynthesis reduces far becomes insignificant.

most of viscaceae bear evergreen leaves photosynthesise effectively, , photosynthesis proceeds within green, fleshy stems well. species, such viscum capense, adapted semi-arid conditions , leaves vestigial scales, hardly visible without detailed morphological investigation. therefore photosynthesis , transpiration take place in stems, limiting demands on host s supply of water, limiting intake of carbon dioxide photosynthesis. accordingly contribution host s metabolic balance becomes trivial , idle parasite may become quite yellow grows, having practically given photosynthesis.

at extreme other species have vigorous green leaves. not photosynthesize actively, heavy infestation of mistletoe plants may take on whole host tree branches, killing practically entire crown , replacing own growth. in such tree host relegated purely supply of water , mineral nutrients , physical support of trunk. such tree may survive viscum community years; resembles totally unknown species unless 1 examines closely, because foliage not of tree. example of species behaves viscum continuum.

a mistletoe seed germinates on branch of host tree or shrub, , in stages of development independent of host. commonly has 2 or 4 embryos, each producing hypocotyl, grows towards bark of host under influence of light , gravity, , potentially each forming mistletoe plant in clump. possibly adaptation assist in guiding process of growing away light, adhesive on seed tends darken bark. on having made contact bark, hypocotyl, rudimentary scrap of root tissue @ tip penetrates it, process may take year or more. in mean time plant dependent on own photosynthesis. after reaches host s conductive tissue can begin rely on host needs. later forms haustorium penetrates host tissue , takes water , nutrients host plant.

species more or less parasitic include leafless quintral, tristerix aphyllus, lives deep inside sugar-transporting tissue of spiny cactus, appearing show tubular red flowers, , genus arceuthobium (dwarf mistletoe; santalaceae) has reduced photosynthesis; adult, manufactures small proportion of sugars needs own photosynthesis, seedling actively photosynthesizes until connection host established.

some species of largest family, loranthaceae, have small, insect-pollinated flowers (as santalaceae), others have spectacularly showy, large, bird-pollinated flowers.

most mistletoe seeds spread birds eat seeds (in actuality drupes). quite range of birds feed on them, of mistle thrush best-known in europe, phainopepla in southwestern north america, , dicaeum of asia , australia. depending on species of mistletoe , species of bird, seeds regurgitated crop, excreted in droppings, or stuck bill, bird wipes onto suitable branch. seeds coated sticky material called viscin. viscin remains on seed , when touches stem, sticks tenaciously. viscin hardens , attaches seed firmly future host, germinates , haustorium penetrates sound bark.

specialist mistletoe eaters have adaptations expedite process; pass seeds through unusually shaped digestive tracts fast pause defecation of seeds part of feeding routine. others have adapted patterns of feeding behavior; bird grips fruit in bill , squeezes sticky-coated seed out side. seed sticks beak , bird wipes off onto branch.

biochemically, viscin complex adhesive mix containing cellulosic strands , mucopolysaccharides.

once mistletoe plant established on host, possible save valuable branch pruning , judicious removal of wood invaded haustorium, if infection caught enough. species of mistletoe can regenerate if pruning leaves of haustorium alive in wood.