Epiphyte (Greek epi upon and phyton plant) means any plant that grows on another plant using it only as a support, but not parasitic . 1 These plants are sometimes called "air plants" because they do not take root on the ground . However, there are many species of algae , including seaweed, that are epiphytes on other aquatic species (marine or aquatic angiosperms ).
Epiphytes use photosynthesis to provide energy and (the non-aquatic) obtain moisture from the air or rain that is deposited on the surface of its host.
The roots can be developed primarily for adherence and specialized structures (such as scales and cups) are those that collect and hold moisture.
Epiphytes are not parasitic on their host, but grow independently obtained only physical support. The most obvious advantage over other herbs restricted to land is receiving more light on the shadowy ecosystems forest and stay away from herbivores. However, they can grow so tightly that come to damage the host plant.
The best-known epiphytes include mosses , lichens , orchids , ferns and bromeliads (such as Tillandsia ), but can be found in all major groups of the vegetable kingdom. Accumulations of large epiphytes occur most abundantly in tropical rainforests and temperate rainforests, but both are lichens and mosses in any environment with trees .
The first major monograph on the ecology of epiphytes was written by Andreas Schimper ( Die Vegetation epiphytische Amerikas, 1888 ).
Epiphytes are one of the six subdivisions of Raunkiaer system .
In Botany , the episperm or seed coat is the layer that surrounds the seed of plants spermatophytes . In the commonly observed episperm two layers, the outer, the testa , derived from internal and external casings, the tegmen , derived from the integument of the ovule and / or the nucellus . Its function is to protect the seed of the environment. Some seed coat forming projections which favor absorption of water at the time the germination or which act as additional protection. In almost all seeds, the micropyle through which had penetrated the pollen tube into the egg, persists as a small hole in the head. In angiosperms , a funiculus binds placenta seed to the inside wall of the fruit . When removing the seed is a small scar or thread that marks the insertion point in the funiculus. 1
In some gymnosperms such as Ginkgo and Cycas , the seed coat has a soft, fleshy and is called "sarcotesta." This can be vascularized sarcotesta present odor oils or releasing butyric acid , as in the case of Ginkgo biloba .
In angiosperms the episperm is generally dry. Seeds Orchidaceae are microscopic and have a simplified seedcoat formed by a sheet of transparent cells which form a thin air bag which is suspended the undifferentiated embryo surrounded by the inner integument atrophied, there is no reserve tissues. In Gossypium (cotton) and Ceiba (palo borracho) seminal epidermis develops long hairs that form the "fiber" cotton. The head consists of several layers, one of which is composed of sclereids arranged as a palisade columnar without intercellular spaces (also called Malpighian cells who first described them first). The tegmen is reduced to the inner epidermis is the innermost layer of episperm. Episperm is frequently mucilaginous, as in the flax or tomato . In Linum usitatissimum the external casings has three layers, the secondary external wall of the epidermal cells elongated radially is formed of a mucilaginous substance which is deposited in layers to fill almost the interior of cells. This substance swells when it absorbs water strongly, and ends up breaking the cutinized outer layers and the cuticle. The two inner layers are parenchyma. Tegment has three layers: the outer layer is mechanical, formed by sclereids oriented parallel to the major axis of the seed. Below is elongated parenchyma cells perpendicular to the sclereids. Cells have the innermost layer filled lumen pigments which determine the color of the seeds. In hard seeds, such as Crotalaria , the episperm is very strong, has a remarkable and is esclerificada cuticle. May consist of several layers of sclereids. In the episperm indehiscent nut is thin and membranaceous, can be reduced to a layer of cells, as in the Umbelliferae or Lactuca or disappear as in the corn .
In plant histology , the sclereids are cells with thick secondary cell wall forming part of the sclerenchyma . But may have very irregular shapes, are usually more or less isodiametric. Its mission is to provide highly lignified tissue stiffness (very hard) and the endocarp of stone fruits. However, forming nodules can be found in parenchymatous tissues relatively soft, such as the cortex of the stem of the walnut , or isolated, such as those that can be found in the mesocarp of the pear .
Can originate from cells of the meristem essential to individualize too early primordia of sclereids. The sclereids of vascular tissues - xylem and phloem - arising from arising from procambium or cambium . The epidermis of the stem from the protodermis . Sclerosis may be caused secondarily by parenchymal cells, such as those presented in the secondary phloem.
The dead cells are generally sclereids maturity, but in some cases, can retain their cytoplasm for long periods of time (up to 5 years). The secondary cell walls are lignified. The cell wall thickness varies, it can sometimes be so thick that it fills almost completely the cell lumen. You may submit scores simple or branched.
The sclereids are widely distributed in the plant body. In the stem the sclereids are found isolated or in groups in the cortex and medulla of dicots and gymnosperms , as well as in the medullary rays or phloem. In the sheet the presence of sclereids in the mesophyll of the leaf blade is characteristic of some tropical plants. May occur at the end of the vascular bundles or completely through the cloud. In the leaves of some monocots , the epidermis is composed of sclereids, as in the scales together the garlic . In the result the scattered sclereids are found in groups or in the fleshy, soft, some knobs , giving the characteristic gritty texture of the pear or quince . They also constitute the endocarp of drupes , as in the peach and plum . In the nuts are hard walls, as in cypsela lettuce. In the seeds of sclereids are found in abundance resulting hardness and consistency to episperm , for example into the epidermis of seeds of pea .
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