Transcript Carnivorous plants - МГ "Константин Величков"

Carnivorous
plants
Carnivorous plants are plants that
derive some or most of their
nutrients (but not energy) from
trapping and consuming animals or
protozoans, typically insects and
other arthropods. Carnivorous plants
appear adapted to grow in places
where the soil is thin or poor in
nutrients, especially nitrogen, such as
acidic bogs and rock outcroppings.
Charles Darwin wrote the first wellknown treatise on carnivorous plants
in 1875.
True carnivory is thought to have evolved independently six times
in five different orders of flowering plants, and these are now
represented by more than a dozen genera. These include about 630
species that attract and trap prey, produce digestive enzymes, and
absorb the resulting available nutrients. Additionally, over 300
protocarnivorous plant species in several genera show some but not
all these characteristics.
Five basic trapping
mechanisms are found in
carnivorous plants
1.
2.
3.
4.
5.
Pitfall traps (pitcher plants) trap prey in a rolled
leaf that contains a pool of digestive enzymes or
bacteria.
Flypaper traps use a sticky mucilage
Snap traps utilize rapid leaf movements
Bladder traps suck in prey with a bladder that
generates an internal vacuum
Lobster-pot traps force prey to move towards a
digestive organ with inward-pointing hairs
These traps may be active or
passive, depending on whether
movement aids the capture of
prey. For example,
Triphyophyllum is a passive
flypaper that secretes mucilage,
but whose leaves do not grow or
move in response to prey
capture. Meanwhile, sundews are
active flypaper traps whose
leaves undergo rapid acid growth,
which is an expansion of
individual cells as opposed to cell
division. The rapid acid growth
allows the sundew tentacles to
bend, aiding in the retention and
digestion of prey
Pitfall traps
Heliamphora, the sun pitche
plant. In this genus, the traps
are clearly derived evolutionarily
from a simple rolled leaf whose
margins have sealed together.
These plants live in areas of high
rainfall in South America such as
Mount Roraima and consequently
have a problem ensuring their
pitchers do not overflow. To
counteract this problem, natural
selection has favoured the
evolution of an overflow similar
to that of a bathroom sink—a
small gap in the zipped-up leaf
margins allows excess water to
flow out of the pitcher.
Heliamphora
Heliamphora is a member of the
Sarraceniaceae, a New World
family in the order
Ericales(heathers and allies).
Heliamphora is limited to South
America, but the family
contains two other genera,
Sarracenia and Darlingtonia,
which are endemic to the
Southeastern United States
(with the exception of one
species) and California
respectively. S. purpurea subsp.
purpurea (the northern pitcher
plant) has a more cosmopolitan
distribution, found as far north
as Canada.
Sarracenia is the pitcher plant genus most
commonly encountered in cultivation, because
it is relatively hardy and easy to grow.
Darlingtonia
californica
the cobra plant, possesses an adaptation also
found in Sarracenia psittacina and, to a lesser
extent, in Sarracenia minor: the operculum is
balloon-like and almost seals the opening to
the tube. This balloon-like chamber is pitted
with areolae, chlorophyll-free patches through
which light can penetrate. Insects, mostly
ants, enter the chamber via the opening
underneath the balloon. Once inside, they tire
themselves trying to escape from these false
exits, until they eventually fall into the tube.
Prey access is increased by the "fish tails",
outgrowths of the operculum that give the
plant its name. Some seedling Sarracenia
species also have long, overhanging opercular
outgrowths; Darlingtonia may therefore
represent an example of neoteny.
The second major group of pitcher plants are the
monkey cups or tropical pitcher plants of the genus
Nepenthes. In the hundred or so species of this
genus, the pitcher is borne at the end of a tendril,
which grows as an extension to the midrib of the
leaf. Most species catch insects, although the
larger ones, particularly N. rajah, also occasionally
take small mammals and reptiles. These pitchers
represent a convenient source of food to small
insectivores. N. bicalcarata possesses two sharp
thorns that project from the base of the operculum
over the entrance to the pitcher, providing some
protection from raids by freeloading mammals.
The pitfall trap has evolved independently in
at least two other groups. The Albany
pitcher plant Cephalotus follicularis is a
small pitcher plant from Western Australia,
with moccasin-like pitchers. The rim of its
pitcher's opening (the peristome) is
particularly pronounced (both secrete
nectar) and provides a thorny overhang to
the opening, preventing trapped insects
from climbing out. The lining of most pitcher
plants is covered in a loose coating of waxy
flakes, which are slippery for insects, prey
that are often attracted by nectar bribes
secreted by the peristome and by bright
flower-like anthocyanin patterning. In at
least one species, Sarracenia flava, the
nectar bribe is laced with coniine, a toxic
alkaloid also found in hemlock, which
probably increases the efficiency of the
traps by intoxicating prey.
Flypaper traps
The flypaper trap is
based on a sticky
mucilage, or glue.
The leaf of flypaper
traps is studded with
mucilage-secreting
glands, which may be
short and
nondescript (like
those of the
butterworts), or long
and mobile (like
those of many
sundews). Flypapers
have evolved
independently at
least five times.
Closely related to Drosera is
the Portuguese dewy pine,
Drosophyllum, which differs
from the sundews in being
passive. Its leaves are
incapable of rapid movement
or growth. Unrelated, but
similar in habit, are the
Australian rainbow plants
(Byblis). Drosophyllum is
unusual in that it grows under
near-desert conditions;
almost all other carnivores
are either bog plants or grow
in moist tropical areas.
Recent molecular data (particularly the production of
plumbagin) indicate that the remaining flypaper,
Triphyophyllum peltatum, a member of the
Dioncophyllaceae, is closely related to Drosophyllum and
forms part of a larger clade of carnivorous and noncarnivorous plants with the Droseraceae, Nepenthaceae,
Ancistrocladaceae and Plumbaginaceae. This plant is
usually encountered as a liana, but in its juvenile phase,
the plant is carnivorous. This may be related to a
requirement for specific nutrients for flowering.
The only two active snap traps—the
Venus flytrap (Dionaea muscipula)
and the waterwheel plant
(Aldrovanda vesiculosa)—are
believed to have had a common
ancestor with similar adaptations.
Their trapping mechanism has also
been described as a "mouse trap" or
"man trap", based on their shape or
rapid movement. However, the term
snap trap is preferred as other
designations are misleading,
particularly with respect to the
intended prey. Aldrovanda is aquatic
and specialised in catching small
invertebrates; Dionaea is terrestrial
and catches a variety of arthropods,
including spiders.
Snap
traps
The traps are very similar, with leaves whose terminal section is
divided into two lobes, hinged along the midrib. Trigger hairs (three on
each lobe in Dionaea muscipula, many more in the case of Aldrovanda)
inside the trap lobes are sensitive to touch. When a trigger hair is
bent, stretch-gated ion channels in the membranes of cells at the base
of the trigger hair open, generating an action potential that
propagates to cells in the midrib.These cells respond by pumping out
ions, which may either cause water to follow by osmosis (collapsing the
cells in the midrib) or cause rapid acid growth.The mechanism is still
debated, but in any case, changes in the shape of cells in the midrib
allow the lobes, held under tension, to snap shut,flipping rapidly from
convex to concave and interring the prey. This whole process takes
less than a second. In the Venus flytrap, closure in response to
raindrops and blown-in debris is prevented by the leaves having a
simple memory: for the lobes to shut, two stimul are required, 0.5 to
30 seconds apart.
Bladder
traps
Bladder traps are exclusive to the genus
Utricularia, or bladderworts. The bladders
pump ions out of their interiors. Water
follows by osmosis generating a partial
vacuum inside the bladder. The bladder
has a small opening, sealed by a hinged
door. In aquatic species, the door has a
pair of long trigger hairs. Aquatic
invertebrates such as Daphnia touch these
hairs and deform the door by lever action,
releasing the vacuum. The invertebrate is
sucked into the bladder, where it is
digested. Many species of Utricularia
(such as U. sandersonii) are terrestrial,
growing on waterlogged soil, and their
trapping mechanism is triggered in a
slightly different manner. Bladderworts
lack roots, but terrestrial species have
anchoring stems that resemble them.
Temperate aquatic bladderworts generally
die back to a resting turion during the
winter months, and U. macrorhiza appears
to regulate the number of bladders it
bears in response to the prevailing
nutrient content of its habitat.
Lobster-pot traps
A lobster-pot trap is a chamber that is
easy to enter, and whose exit is either
difficult to find or obstructed by inwardpointing bristles. Lobster pots are the
trapping mechanism in Genlisea, the
corkscrew plants. These plants appear to
specialise in aquatic protozoa. A Y-shaped
modified leaf allows prey to enter but not
exit. Inward-pointing hairs force the prey to
move in a particular direction. Prey entering
the spiral entrance that coils around the
upper two arms of the Y are forced to move
inexorably towards a stomach in the lower
arm of the Y, where they are digested. Prey
movement is also thought to be encouraged
by water movement through the trap,
produced in a similar way to the vacuum in
bladder traps, and probably evolutionarily
related to it.
Borderline carnivores
To be a fully fledged carnivore, a plant must attract, kill, and
digest prey and it must benefit from absorbing the products of
the digestion (mostly amino acids and ammonium ions).To many
horticulturalists, these distinctions are a matter of taste.
There is a spectrum of carnivory found in plants: from
completely non-carnivorous plants like cabbages, to borderline
carnivores, to unspecialised and simple traps, like Heliamphora,
to extremely specialised and complex traps, like that of the
Venus flytrap.
The borderline carnivores include Roridula and Catopsis
berteroniana. Catopsis is a borderline carnivorous
bromeliad, like Brocchinia reducta. However, unlike B.
reducta, which produces the enzyme phosphatase, C.
berteroniana has not been shown to produce any
digestive enzymes at all.In these pitfall traps, prey
simply fall into the urn, assisted by the waxy scales
located on the rim. Roridula has a more intricate
relationship with its prey.
• Презентацията е изработена
от Диана Филчева -8б клас
МГ “Константин Величков”
гр.Пазарджик