Write an essay on pteridophytes horsetail
Write an essay on pteridophytes horsetail
Vegetative Reproduction: The subterranean rhizomes of some species e. Fern tubers were used for food 30, years ago in Europe. There is no pith. But, the sexuality demonstrated by some of the members appears to be related to environmental factors. The outer cell divides by three successive periclinal divisions and in this way a tetrahedral apical cell is formed Fig. Another cross wall forms a quadrant stage producing stem, leaf, foot and root. These relatively young species probably arose along with the other most recent lineages of vascular plants, the angiosperms or flowering plants, another group lacking an extensive fossil record. Equisetum, but Christenhusz et al.
Ferns have large, multiple-veined leaves. Sex Organs of Equisetum: i.
Be Pretty Smell awesome so bees can find you Smell like rotten meat to attract flies if they are your pollinator Be pretty so bees come to you Glow in the UV spectrum to birds and bees can find you Look Like Something Look like a wasp to trick wasps into thinking they found a mate Location Be on the edge of the plant so pollinators can find you Be open so pollinators can get in eearth. New leaves and branches of Equisetum are produced by the apical meristem, however, most of the length of the stem are due to the activity of intercalary meristem located just above each node. The term apogamy was first used by De Bary Ferns are generally not known to be poisonous to humans. The outer two layers i. The central part of the internode of aerial shoot is occupied by a large pith cavity which is formed due to rapid elongation of the internodal region. The germination takes place immediately if the spores land on a suitable substratum. Since then it has been reported in many Pteridophytes e. Strobilus of Northern giant horsetail Equisetum telmateia subsp. The life cycle of a typical fern proceeds as follows: A diploid sporophyte phase produces haploid spores by meiosis a process of cell division which reduces the number of chromosomes by a half. Thus Polypodiopsida in the broad sense sensu lato as used by the PPG Polypodiopsida sensu PPG needs to be distinguished from the narrower usage sensu stricto of Smith et al. The small white protuberances are accumulated silicates on cells. The flower includes male and female reproductive structures. The innermost layer of the sporangial wall differentiates as the tapetum.
The smaller cell elongates and forms the first rhizoid. Diploid 2n fern sporophytes are familiar to most people and are often found as quiet accompaniments in floral arrangements.
Antherozoids can get transferred to the archegonia which are the female sex organs, only in the presence of water. The plant body can be divided into a true root, stem, and leaves.
Apogamy, Apospory and Parthenogenesis: Pteridophytes show heteromorphic alternation of generation. No suspensor is formed in Equisetum. There are about eleven thousand different species of pteridophytes, making them the most diverse land plants after the flowering plants angiosperms. Ducket , in order to explore the sexuality in Equisetum, observed that some of the fragments of male gametophyte remained male throughout the successive subcultures under laboratory conditions. This seed has three main parts: embryo, food supply and seed coat. Therefore, Pteridophytes are also known as amphibians of the plant kingdom. Although most pteridophytes are homosporous produce spores that are all the same size , a few groups are heterosporous with large megaspores and small microspores. It is also one of the world's most important agricultural weeds, especially in the British highlands, and often poisons cattle and horses. The male and female gametes fuse to form zygote which develops into sporophyte. On the leaves sporophylls they may be ventral, marginal Pteris, Adiantum or dorsal e.
While, the venter cell, by a transverse division, forms the ventral canal cell and an egg Fig. They are dorsiventral and consist of a basal non-chlorophyllous cushion-like portion from which a number of erect chlorophyllous muticellular lobes develop upwards.
The epibasal and hypobasal cells then divide at right angles to the oogonial wall, and as a result a tour-celled quadrant stage is established Fig. Then the sporangium splits open by a longitudinal line due to the differential hygroscopic response of the wall cells.
Unicellular rhizoids are formed from the basal cells of cushion Fig.
Spores[ edit ] The spores are borne under sporangiophores in strobilicone-like structures at the tips of some of the stems. The number of leaves per node varies according to the species. Vascular bundles are conjoint, collateral and closed.
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