*eukaryotes beings (from Greek language eu - I, true, and karuon, nucleus), comprising every organism belonging to the four kingdoms of living world: animals, mushrooms, plants and protists (protists: single-celled organisms made up of one or more cells, with distinct nucleus, surrounded by two nuclear membranes), -multi-cellular beings, -and autotrophic beings, with green plants (which are organisms able to synthesize their own food from simple inorganic sources, such as carbon dioxide, water, nitrates), plants that perform photosynthesis with the luminosity and the chlorophylls cells.
Vegetal organisms are made up of cells, as the animals. But we`ll deal with following bodies: - root, - stem, - leaf, - flower, - fruit, - seed.
Plants are divided into two large groups: *cryptogams (in the Greek language, kripto, hidden): plants that have gamete producing structures little evident, *phanerogams (in the Greek language, phanero, evident): they have the gamete producing structures clearly visible, in cone or in flower. These plants are also called spermatophytes.
Functions of the organs :
- The root will anchoring the plant to the ground and absorbing from it water and mineral salts, essential for plant life.
- The stem keeps the plant upright, and inside there are the xylems, vessels which will transport the liquid absorbed by the roots (water + minerals salts + amines) the gross sap, as well as the phloems, vessels that will transport the elaborate sap (substances produced by photosynthesis after the transformation of the gross sap) up to the organs - the roots, the stems, leaves, flowers, fruits and seeds.
In plants having no conductive vessels (algae and mosses), the distribution of sap is made from cell to cell. Most part of the plants has conductive vessels.
- The leaves are, therefore, the part of the plants where photosynthesis (special cells) occurs, which will enable the growth and good adaptation of the vegetal to its environment.
The leaves are also the place where the processes of respiration and transpiration occur.
- The flowers and the seeds are organs related to plants reproduction.
Cryptogams can be divided based on the organization of the body:
***First group
*The thallophytes (plant body destituted of stem, root or own leaves) are plants with undifferentiated structure in root, stem and leaf.
One of the criteria for the classification of algae is the color; with this criteria, they are divided into three parts: -Chlorophyta - green, -Phaeophyta - brown, -Rhodophyta - red.
It`s a group of very great importance because of the amount of oxygen in the atmosphere, and also for other uses in food and cosmetic industry.
***The second group
*The bryophytes (non-vascular and small plants), do not exceed 20 cm in height and have a dependency with water, mostly.
The meeting of both will be done with the help of water (drop). However, the elaborate sap goes directly from one cell to another, throughout their walls. Mosses and Hepaticophytas are the main representatives.
Despite the modest aspect, mosses have a great importance to ecosystems. Along with the lichens, mosses were the first plants to grow on rocks, which erode by substances produced by their biological activity.
Thereby, they allow that, after them, other plants can grow on these same rocks.
***Third group
*The pteridophyta (group of plants without flower) that multiply to form sporangia in modified leaves or not.
They have sap driver vessels allowing fast transport of water and minerals up to the leaves, and also delivering the elaborate sap to the other parts of the plant. Ferns and maidenhair are the main representatives of the group.
The particularity of these plants are the leaves, unfolding from the center of the plant; in general, each leaf of these plants is divided into many smaller parts, called leaflets.
Reproduction is made by means of spores, which are often produced in the sori located on the underside of the leaves. Once on the ground, they will origin a little plant (prothallus), which produces the gametes, that will origin a new plant.
Phanerogams (with ova and pollen, respectively the male and female gametes) and that way, apparent reproductive organs and a seed.
***First group
*The Gymnosperms, that produce strobiles (cone-like formation, around which are sporophytes (micro or mega sporophytes) or specialized scales, as reproductive structures, which are wrongly named flowers (inflorescences) and seeds are naked, i.e. are not encased in fruit (Greek language: gymnos, naked, sperm, seed).
More well-known gymnosperms are the pines, cypresses and redwoods. In Brazil, a native gymnosperm is the araucaria, also known as parana pine. ***Second group
*The Angiosperms, which produce flowers (defined as reproductive organ and seed inside the fruit).
They are also consisted of three main components: - roots, - stem, - and leaves (photosynthesis).
Flowercomposition :
the floral receptacle sits on top of the floral peduncle, which can be called the flower cable. From outside to inside, there are four types of modified leaves, the flower constituents: -the sepals (the outermost, with a floral button protection function), whose set is called the calyx, -the petals, forming the corolla, with the function to call pollinator agents, Those agents, often the insects looking for the nectar, a sugar solution produced by existing glands, generally located at the base of the petals. -the stamens (with a rod, the fillet, supporting the anther, a dilated portion), will be inside of the receptacle. The set of stamens forms the androecium, considered as the male component of the flower; in another part, the anther, are produced the pollen grains, which are originated in the pollinic sacs, released when the anther becomes adult. -the carpel (center of the floral receptacle).
At its peak, the stigma (slight swelling), continuing with a short style, was the extension to the ovary. Inside the ovary, there are ova.
The lone carpel is component of the gynoecium, the female part of the flower carpel.
Fertilization (ova) in flowers will be the (D) Phanerogams (with ova and pollen, respectively the male and female gametes) and that way, apparent reproductive organs and a seed.
In the group of Gymnosperms, sexual reproduction includes the various phenomena : - sporogenesis, - gametogenesis, - pollination, - fertilization, - and development of the seed and the fruit.
Angiosperms are known as fruit plants.
This is the group of plants, with largest number of species (aquatic species, species adapted to all environments).
Two groups compose the angiosperms:
The cotyledons are modified leaves that are part of the body of the embryo and can store nutrients by the development during early stages.
*monocotyledons
The characteristics of the components of the plants are, in this case: -flower with 3 or multiple elements, -stem growing in height and not in thickness, in general, and distribution of vessels in libero-ligneous beams, scattered into irregular distribution, -leaf - invaginating: developed sheath; one or parallel leaf veins, reticulated or pinnate ribs, -root fasciculata ('hair'), examples: pineapple, garlic, rice, bamboo, palm trees in general, ...
*dicotyledons -flower with dimerous, tetramerous or pentamerous, -stem with growth in thickness (trunk), in general,
distribution of vessels in libero-wood beams, arranged in a circle (regular = eusthelical distribution), -petiolate sheet: reduced sheath; petiole, reticulated leaf veins or pinnate ribs, -swivel or axial root (main), examples: avocado, cotton, cocoa, eucalyptus, beans, ...
Seed Formation
Angiosperms - type species - fertilization happens when the male nucleus (pollen grain) and the female one (ovary`s oosphere) meet to form the zygote, still in the ovary of the flower.
The zygote, a simple cell, suffers then many cell divisions and gives origin to a small multi-cellular embryo.
Fertilized ovum develops into a seed. The formation of one or more seeds inside an ovary causes its development, until reaching the fruit.
Classification of flowers
The flowers are classified according to various criteria.
For example:
*Criterion - flowers sex -Hermaphrodite or monoclinous - with the two sexes, androecium and gynoecium (examples: carnation, orange tree, ...). -Unisexual - only androecium or gynoecium (examples: pumpkin, papaya, ...). -Sterile: If having androecium or gynoecium are not fertile or they do not present.
*Criterion - Pollinator agent -Entomophily - pollination by insects. -Zoophily - pollination by birds or bats -Anthropophily - pollination by man. -Anemophily - pollination by the wind.
