Cyclamen is a genus of 23 species of perennial flowering plants in the family Primulaceae. Cyclamen species are native to Europe and the Mediterranean Basin east to Iran, with one species in Somalia, they grow from tubers and are valued for their flowers with upswept petals and variably patterned leaves. It was traditionally classified in the family Primulaceae, was reclassified in the family Myrsinaceae in 2000, in 2009 with the introduction of the APG III system, was returned to the subfamily Myrsinoideae within the family Primulaceae. Cyclamen is Medieval Latin, from earlier Latin cyclamīnos, from Ancient Greek κυκλάμινος, kyklā́mīnos from κύκλος, kýklos "circle", because of the round tuber. In English, the species of the genus are called by the genus name. In many languages, cyclamen species are colloquially called by a name like the English sowbread, or swinebread, based on Medieval Latin panis porcinus: Saubrot in German, pain de pourceau in French, pan porcino in Italian, varkensbrood in Dutch, "pigs' manjū" in Japanese.
Cyclamens have a tuber, from which the leaves and roots grow. In most species, leaves come up in autumn, grow through the winter, die in spring the plant goes dormant through the dry Mediterranean summer; the storage organ of the cyclamen is a round tuber. It is mistakenly called a corm, but a corm has a papery tunic and a basal plate from which the roots grow; the storage organ of the cyclamen has no papery covering and, depending on the species, roots may grow out of any part. It is therefore properly classified as a tuber; the tuber may produce roots depending on the species. Cyclamen persicum and Cyclamen coum root from the bottom. Cyclamen graecum has thick anchor roots on the bottom; the shape of the tuber may be near spherical, as in Cyclamen coum or flattened, as in Cyclamen hederifolium. In some older specimens of Cyclamen purpurascens and Cyclamen rohlfsianum, growing points on the tuber become separated by shoulders of tissue, the tuber becomes misshapen. In most other species, the tuber is round in old age.
Leaves and flowers sprout from growing points on the top of the tuber. Growing points that have lengthened and become like woody stems are known as floral trunks; the size of the tuber varies depending on species. In Cyclamen hederifolium, older tubers reach 24 cm across, but in Cyclamen parviflorum, tubers do not grow larger than 2 cm across. Leaves sprout from floral trunks on top of the tuber; each leaf grows on its own stem. Leaf stems in early growth may be distinguished from flower stems by the direction their tips curl: tips of leaf stems curl upwards, while tips of flower stems curl downwards; the shape of the leaves varies between the species, between different specimens of the same species. Cyclamen hederifolium and Cyclamen repandum have leaves shaped like ivy, with angles and lobes, Cyclamen coum has nearly round leaves, Cyclamen persicum has heart-shaped leaves with a pointed tip; the leaf margin may be smooth, as in Cyclamen coum subsp. Coum, or finely toothed, as in Cyclamen graecum.
The color of the upper side of leaves is variable within a species. Most species have leaves variegated in several shades of green and silver, either in an irregular pattern of blotches or an arrowhead or Christmas tree shape. In cultivation, cyclamens species other than Cyclamen persicum, are selected as or more for striking or unusual leaf patterns than for their flowers; the lower side of leaves is shiny, its color varies from plain green to rich red or purple. Most cyclamen species originate from the Mediterranean, where summers are hot and dry and winters are cool and wet, are summer-dormant: their leaves sprout in the autumn, remain through the winter, wither the next spring. Cyclamen purpurascens and Cyclamen colchicum, originate from cooler regions in mountains, their leaves remain through the summer and wither only after the next year's leaves have developed. Flowering time may be any month of the year, depending on the species. Cyclamen hederifolium and Cyclamen purpurascens bloom in summer and autumn, Cyclamen persicum and coum bloom in winter, Cyclamen repandum blooms in spring.
Each flower is on a stem coming from a growing point on the tuber. In all species, the stem is bent 150-180° at the tip, so that the nose of the flower faces downwards. Cyclamen hederifolium'Stargazer' is an exception to this. Flowers have 5 petals, bent outwards or up, sometimes twisted, connected at the base into a cup, five sepals behind the cup. Petal shape varies depending on species, sometimes within the same species. Cyclamen repandum has petals much longer than wide, Cyclamen coum has stubby round petals, Cyclamen hederifolium has petals with proportions between the two. Petal color may be white, pink, or purple with darker color on the nose. Many species have a pink form and a white form, but a few have only one color, such as Cyclamen balearicum, always white; the dark color on the flower nose varies in shape: Cyclamen persicum has a smooth band, Cyclamen hederifolium has a streaky V, Cyclamen coum has an M-shaped splotch with two white or pink "eyes" beneath. In some species, such as Cyclamen hederifolium, the petal edges at the nose are curved outwards into auricles.
Most species, like Cyclamen persicum, have no auricles. In most species, the style protrudes 1–3 mm
The onion known as the bulb onion or common onion, is a vegetable, the most cultivated species of the genus Allium. Its close relatives include the garlic, leek and Chinese onion; this genus contains several other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion, the tree onion, the Canada onion. The name "wild onion" is applied to a number of Allium species, but A. cepa is known from cultivation. Its ancestral wild original form is not known, although escapes from cultivation have become established in some regions; the onion is most a biennial or a perennial plant, but is treated as an annual and harvested in its first growing season. The onion plant has a fan of hollow, bluish-green leaves and its bulb at the base of the plant begins to swell when a certain day-length is reached; the bulbs are composed of shortened, underground stems surrounded by fleshy modified scale that envelop a central bud at the tip of the stem. In the autumn, the foliage dies down and the outer layers of the bulb become dry and brittle.
The crop is harvested and dried and the onions are ready for use or storage. The crop is prone to attack by a number of pests and diseases the onion fly, the onion eelworm, various fungi cause rotting; some varieties of A. cepa, such as shallots and potato onions, produce multiple bulbs. Onions are used around the world; as a food item, they are served cooked, as a vegetable or part of a prepared savoury dish, but can be eaten raw or used to make pickles or chutneys. They are pungent when contain certain chemical substances which irritate the eyes; the onion plant known as the bulb onion or common onion, is the most cultivated species of the genus Allium. It was first described by Carl Linnaeus in his 1753 work Species Plantarum. A number of synonyms have appeared in its taxonomic history: Allium cepa var. aggregatum – G. Don Allium cepa var. bulbiferum – Regel Allium cepa var. cepa – Linnaeus Allium cepa var. multiplicans – L. H. Bailey Allium cepa var. proliferum – Regel Allium cepa var. solaninum – Alef Allium cepa var. viviparum – Mansf.
A. Cepa is known from cultivation, but related wild species occur in Central Asia; the most related species include A. vavilovii and A. asarense from Iran. However and Hopf state that "there are doubts whether the A. vavilovii collections tested represent genuine wild material or only feral derivatives of the crop."The vast majority of cultivars of A. cepa belong to the "common onion group" and are referred to as "onions". The Aggregatum group of cultivars includes both shallots and potato onions; the genus Allium contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion, Egyptian onion, Canada onion. Cepa is accepted as Latin for "onion" and has an affinity with Ancient Greek: κάπια and Albanian: qepë and is ancestral to Aromanian: tseapã, Catalan: ceba, Occitan: ceba, Spanish: cebolla, Romanian: ceapă; the English word chive is derived from the Old French cive, which derived from cepa. The onion plant has been selectively bred in cultivation for at least 7,000 years.
It is a biennial plant, but is grown as an annual. Modern varieties grow to a height of 15 to 45 cm; the leaves are yellowish - to bluish green and grow alternately in a fan-shaped swathe. They are fleshy and cylindrical, with one flattened side, they are at their broadest about a quarter of the way up, beyond which they taper towards a blunt tip. The base of each leaf is a flattened white sheath that grows out of a basal disc. From the underside of the disc, a bundle of fibrous roots extends for a short way into the soil; as the onion matures, food reserves begin to accumulate in the leaf bases and the bulb of the onion swells. In the autumn, the leaves die back and the outer scales of the bulb become dry and brittle, so the crop is normally harvested. If left in the soil over winter, the growing point in the middle of the bulb begins to develop in the spring. New leaves appear and a long, hollow stem expands, topped by a bract protecting a developing inflorescence; the inflorescence takes the form of a globular umbel of white flowers with parts in sixes.
The seeds are glossy triangular in cross section. The average pH of an onion is around 5.5 Because the wild onion is extinct and ancient records of using onions span western and eastern Asia, the geographic origin of the onion is uncertain, with domestication worldwide. Food uses of onions date back thousands of years in China and Persia. Traces of onions recovered from Bronze Age settlements in China suggest that onions were used as far back as 5000 BCE, not only for their flavour, but the bulb's durability in storage and transport. Ancient Egyptians revered the onion bulb, viewing its spherical shape and concentric rings as symbols of eternal life. Onions were used in Egyptian burials, as evidenced by onion traces found in the eye sockets of Ramesses IV. Pliny the Elder of the first century CE wrote about the use of onions and cabbage in Pompeii, he documented Roman beliefs about the onion's ability to improve ocular ailments, aid in sleep, heal everything from oral sores and toothaches to dog bites and dysentery.
Soil is a mixture of organic matter, gases and organisms that together support life. Earth's body of soil, called the pedosphere, has four important functions: as a medium for plant growth as a means of water storage and purification as a modifier of Earth's atmosphere as a habitat for organismsAll of these functions, in their turn, modify the soil; the pedosphere interfaces with the lithosphere, the hydrosphere, the atmosphere, the biosphere. The term pedolith, used to refer to the soil, translates to ground stone in the sense "fundamental stone". Soil consists of a solid phase of minerals and organic matter, as well as a porous phase that holds gases and water. Accordingly, soil scientists can envisage soils as a three-state system of solids and gases. Soil is a product of several factors: the influence of climate, relief and the soil's parent materials interacting over time, it continually undergoes development by way of numerous physical and biological processes, which include weathering with associated erosion.
Given its complexity and strong internal connectedness, soil ecologists regard soil as an ecosystem. Most soils have a dry bulk density between 1.1 and 1.6 g/cm3, while the soil particle density is much higher, in the range of 2.6 to 2.7 g/cm3. Little of the soil of planet Earth is older than the Pleistocene and none is older than the Cenozoic, although fossilized soils are preserved from as far back as the Archean. Soil science has two basic branches of study: pedology. Edaphology studies the influence of soils on living things. Pedology focuses on the formation and classification of soils in their natural environment. In engineering terms, soil is included in the broader concept of regolith, which includes other loose material that lies above the bedrock, as can be found on the Moon and on other celestial objects as well. Soil is commonly referred to as earth or dirt. Soil is a major component of the Earth's ecosystem; the world's ecosystems are impacted in far-reaching ways by the processes carried out in the soil, from ozone depletion and global warming to rainforest destruction and water pollution.
With respect to Earth's carbon cycle, soil is an important carbon reservoir, it is one of the most reactive to human disturbance and climate change. As the planet warms, it has been predicted that soils will add carbon dioxide to the atmosphere due to increased biological activity at higher temperatures, a positive feedback; this prediction has, been questioned on consideration of more recent knowledge on soil carbon turnover. Soil acts as an engineering medium, a habitat for soil organisms, a recycling system for nutrients and organic wastes, a regulator of water quality, a modifier of atmospheric composition, a medium for plant growth, making it a critically important provider of ecosystem services. Since soil has a tremendous range of available niches and habitats, it contains most of the Earth's genetic diversity. A gram of soil can contain billions of organisms, belonging to thousands of species microbial and in the main still unexplored. Soil has a mean prokaryotic density of 108 organisms per gram, whereas the ocean has no more than 107 procaryotic organisms per milliliter of seawater.
Organic carbon held in soil is returned to the atmosphere through the process of respiration carried out by heterotrophic organisms, but a substantial part is retained in the soil in the form of soil organic matter. Since plant roots need oxygen, ventilation is an important characteristic of soil; this ventilation can be accomplished via networks of interconnected soil pores, which absorb and hold rainwater making it available for uptake by plants. Since plants require a nearly continuous supply of water, but most regions receive sporadic rainfall, the water-holding capacity of soils is vital for plant survival. Soils can remove impurities, kill disease agents, degrade contaminants, this latter property being called natural attenuation. Soils maintain a net absorption of oxygen and methane and undergo a net release of carbon dioxide and nitrous oxide. Soils offer plants physical support, water, temperature moderation and protection from toxins. Soils provide available nutrients to plants and animals by converting dead organic matter into various nutrient forms.
A typical soil is about 50% solids, 50% voids of which half is occupied by water and half by gas. The percent soil mineral and organic content can be treated as a constant, while the percent soil water and gas content is considered variable whereby a rise in one is balanced by a reduction in the other; the pore space allows for the infiltration and movement of air and water, both of which are critical for life existing in soil. Compaction, a common problem with soils, reduces this space, preventing air and water from reaching plant roots and soil organisms. Given sufficient time, an undifferentiated soil will evolve a soil profile which consists of two or more layers, referred to as soil horizons, that differ in one or more properties such as in their texture, density, consistency, temperature and reactivity; the horizons differ in thickness and gene
Tubers are enlarged structures in some plant species used as storage organs for nutrients. They are used for the plant's perennation, to provide energy and nutrients for regrowth during the next growing season, as a means of asexual reproduction. Stem tubers form thickened stolons. Common plant species with stem tubers include yam; some sources treat modified lateral roots under the definition. The term originates from Latin tuber, meaning "lump, swelling"; some sources define the term "tuber" to mean only structures derived from stems. A stem tuber forms from thickened stolons; the top sides of the tuber produce shoots that grow into typical stems and leaves and the under sides produce roots. They tend to form at the sides of the parent plant and are most located near the soil surface; the underground stem tuber is a short-lived storage and regenerative organ developing from a shoot that branches off a mature plant. The offsprings or new tubers are attached to a parent tuber or form at the end of a hypogeogenous rhizome.
In the autumn the plant dies, except for the new offspring stem tubers which have one dominant bud, which in spring regrows a new shoot producing stems and leaves, in summer the tubers decay and new tubers begin to grow. Some plants form smaller tubers and/or tubercules which act like seeds, producing small plants that resemble seedlings; some stem tubers are long-lived, such as those of tuberous begonia, but many plants have tubers that survive only until the plants have leafed out, at which point the tuber is reduced to a shriveled-up husk. Stem tubers start off as enlargements of the hypocotyl section of a seedling but sometimes include the first node or two of the epicotyl and the upper section of the root; the stem tuber has a vertical orientation with one or a few vegetative buds on the top and fibrous roots produced on the bottom from a basal section the stem tuber has an oblong rounded shape. Tuberous begonia and Cyclamen are grown stem tubers. Mignonette vine produces aerial stem tubers on 12-to-25-foot-tall vines, the tubers fall to the ground and grow.
Plectranthus esculentus of the mint family Lamiaceae, produces tuberous under ground organs from the base of the stem, weighing up to 1.8 kg per tuber, forming from axillary buds producing short stolons that grow into tubers. Potatoes are stem tubers. Enlarged stolons thicken to develop into storage organs; the tuber has all the parts including nodes and internodes. The nodes are the eyes and each has a leaf scar; the nodes or eyes are arranged around the tuber in a spiral fashion beginning on the end opposite the attachment point to the stolon. The terminal bud is produced at the farthest point away from the stolon attachment and tubers thus show the same apical dominance as a normal stem. Internally, a tuber is filled with starch stored in enlarged parenchyma like cells; the inside of a tuber has the typical cell structures of any stem, including a pith, vascular zones, a cortex. The tuber is produced in one growing season and used to perennate the plant and as a means of propagation; when fall comes, the above-ground structure of the plant dies, but the tubers survive over winter underground until spring, when they regenerate new shoots that use the stored food in the tuber to grow.
As the main shoot develops from the tuber, the base of the shoot close to the tuber produces adventitious roots and lateral buds on the shoot. The shoot produces stolons that are long etiolated stems; the stolon elongates during long days with the presence of high auxins levels that prevent root growth off of the stolon. Before new tuber formation begins, the stolon must be a certain age; the enzyme lipoxygenase makes a hormone, jasmonic acid, involved in the control of potato tuber development. The stolons are recognized when potato plants are grown from seeds; as the plants grow, stolons are produced around the soil surface from the nodes. The tubers form close to the soil surface and sometimes on top of the ground; when potatoes are cultivated, the tubers are planted much deeper into the soil. Planting the pieces deeper creates more area for the plants to generate the tubers and their size increases; the pieces sprout shoots. These shoots generate short stolons from the nodes while in the ground.
When the shoots reach the soil surface, they produce roots and shoots that grow into the green plant. A tuberous root or storage root, is a modified lateral root, enlarged to function as a storage organ; the enlarged area of the root-tuber, or storage root, can be produced at the end or middle of a root or involve the entire root. It is thus similar in function and appearance to a stem tuber. Examples of plants with notable tuberous roots include the sweet potato and dahlia. Root tubers are perennating organs, thickened roots that store nutrients over periods when the plant cannot grow, thus permitting survival from one year to the next; the massive enlargement of secondary roots represented by sweet potato, have the internal and external cell and tissue structures of a normal root, they produce adventitious roots and stems which again produce adventitious roots. In root-tubers, there are reduced leaves. Root tubers have one end called the proximal end, the end
The dicotyledons known as dicots, are one of the two groups into which all the flowering plants or angiosperms were divided. The name refers to one of the typical characteristics of the group, namely that the seed has two embryonic leaves or cotyledons. There are around 200,000 species within this group; the other group of flowering plants were called monocotyledons or monocots having one cotyledon. These two groups formed the two divisions of the flowering plants. From the 1990s onwards, molecular phylogenetic research confirmed what had been suspected, namely that dicotyledons are not a group made up of all the descendants of a common ancestor. Rather, a number of lineages, such as the magnoliids and groups now collectively known as the basal angiosperms, diverged earlier than the monocots did; the traditional dicots are thus a paraphyletic group. The largest clade of the dicotyledons are known as the eudicots, they are distinguished from all other flowering plants by the structure of their pollen.
Other dicotyledons and monocotyledons have monosulcate pollen, or forms derived from it, whereas eudicots have tricolpate pollen, or derived forms, the pollen having three or more pores set in furrows called colpi. Aside from cotyledon number, other broad differences have been noted between monocots and dicots, although these have proven to be differences between monocots and eudicots. Many early-diverging dicot groups have "monocot" characteristics such as scattered vascular bundles, trimerous flowers, non-tricolpate pollen. In addition, some monocots have dicot characteristics such as reticulated leaf veins. Traditionally the dicots have been called the Dicotyledones, at any rank. If treated as a class, as in the Cronquist system, they could be called the Magnoliopsida after the type genus Magnolia. In some schemes, the eudicots were treated as a separate class, the Rosopsida, or as several separate classes; the remaining dicots may be kept in a single paraphyletic class, called Magnoliopsida, or further divided.
Some botanists prefer to retain the dicotyledons as a valid class, arguing its practicality and that it makes evolutionary sense. The following lists show the orders in the Angiosperm Phylogeny Group APG IV system traditionally called dicots, together with the older Cronquist system. In the Dahlgren and the Thorne systems, the subclass name Magnoliidae was used for the dicotyledons; this is the case in some of the systems derived from the Cronquist system. For each system, only the superorders are listed; the sequence of each system has been altered to pair corresponding taxa, although circumscription of superorders with the same name is not always the same. The Thorne system as depicted by Reveal is: Calyciflorae World list of dicot species via the Catalogue of Life Tree browser for dicot orders and genera with species counts and estimates via the Catalogue of Life
A storage organ is a part of a plant modified for storage of energy or water. Storage organs grow underground, where they are better protected from attack by herbivores. Plants that have an underground storage organ are called geophytes in the Raunkiær plant life-form classification system. Storage organs but not always, act as perennating organs which enable plants to survive adverse conditions. Storage organs may act as perennating organs; these are used by plants to survive adverse periods in the plant's life-cycle. During these periods, parts of the plant die and when conditions become favourable again, re-growth occurs from buds in the perennating organs. For example, geophytes growing in woodland under deciduous trees die back to underground storage organs during summer when tree leaf cover restricts light and water is less available. However, perennating organs need not be storage organs. After losing their leaves, deciduous trees grow them again from'resting buds', which are the perennating organs of phanerophytes in the Raunkiær classification, but which do not act as storage organs.
Storage organs need not be perennating organs. Many succulents have leaves adapted for water storage. In common parlance, underground storage organs may be generically called roots, tubers, or bulbs, but to the botanist there is more specific technical nomenclature: True roots: Tuberous root or root tuber — e.g. Dahlia Storage taproot — e.g. carrot Modified stems: Corm — e.g. Crocus Stem tuber — e.g. Zantedeschia, potato Rhizome — e.g. Iris pseudacorus Pseudobulb — e.g. Pleione Caudex — e.g. Adenium Others: Storage hypocotyl — sometimes called a tuber, as in Cyclamen Bulb — e.g. Lilium, onionSome of the above pseudobulbs and caudices, may occur wholly or above ground. Intermediates and combinations of the above are found, making classification difficult; as an example of an intermediate, the tuber of Cyclamen arises from the stem of the seedling, which forms the junction of the roots and stem of the mature plant. In some species roots come from the bottom of the tuber; as an example of a combination, juno irises have both bulbs and storage roots.
Underground storage organs used for food may be generically called root vegetables, although this phrase should not be taken to imply that the class only includes true roots. Succulents are plants which are adapted to withstand periods of drought by their ability to store moisture in specialized storage organs. Leaf succulents store water in their leaves, which are thus thickened and covered with a waxy coating or fine hairs to reduce evaporation, they may contain mucilaginous compounds. Some leaf succulents have leaves which are distributed along the stem in a similar fashion to non-succulent species. In others, the leaves are more compact. Pebble-plants or living stones have reduced their leaves to just two, forming a fleshy body, only the top of which may be visible above ground. Stem succulents are either leafless or have leaves which can be shed in the event of drought. Photosynthesis is taken over by the stems; as with leaf succulents, stems may be covered with a waxy coating or fine hairs to reduce evaporation.
The ribbed bodies of cacti may be an adaption to allow shrinkage and expansion with the amount of water stored. Plants of the same general form as cacti are found in other families
A seed is an embryonic plant enclosed in a protective outer covering. The formation of the seed is part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosperm plants. Seeds are the product of the ripened ovule, after fertilization by pollen and some growth within the mother plant; the embryo is developed from the seed coat from the integuments of the ovule. Seeds have been an important development in the reproduction and success of gymnosperm and angiosperm plants, relative to more primitive plants such as ferns and liverworts, which do not have seeds and use water-dependent means to propagate themselves. Seed plants now dominate biological niches on land, from forests to grasslands both in hot and cold climates; the term "seed" has a general meaning that antedates the above – anything that can be sown, e.g. "seed" potatoes, "seeds" of corn or sunflower "seeds". In the case of sunflower and corn "seeds", what is sown is the seed enclosed in a shell or husk, whereas the potato is a tuber.
Many structures referred to as "seeds" are dry fruits. Plants producing berries are called baccate. Sunflower seeds are sometimes sold commercially while still enclosed within the hard wall of the fruit, which must be split open to reach the seed. Different groups of plants have other modifications, the so-called stone fruits have a hardened fruit layer fused to and surrounding the actual seed. Nuts are the one-seeded, hard-shelled fruit of some plants with an indehiscent seed, such as an acorn or hazelnut. Seeds are produced in several related groups of plants, their manner of production distinguishes the angiosperms from the gymnosperms. Angiosperm seeds are produced in a hard or fleshy structure called a fruit that encloses the seeds for protection in order to secure healthy growth; some fruits have layers of both fleshy material. In gymnosperms, no special structure develops to enclose the seeds, which begin their development "naked" on the bracts of cones. However, the seeds do become covered by the cone scales.
Seed production in natural plant populations varies from year to year in response to weather variables and diseases, internal cycles within the plants themselves. Over a 20-year period, for example, forests composed of loblolly pine and shortleaf pine produced from 0 to nearly 5 million sound pine seeds per hectare. Over this period, there were six bumper, five poor, nine good seed crops, when evaluated for production of adequate seedlings for natural forest reproduction. Angiosperm seeds consist of three genetically distinct constituents: the embryo formed from the zygote, the endosperm, triploid, the seed coat from tissue derived from the maternal tissue of the ovule. In angiosperms, the process of seed development begins with double fertilization, which involves the fusion of two male gametes with the egg cell and the central cell to form the primary endosperm and the zygote. Right after fertilization, the zygote is inactive, but the primary endosperm divides to form the endosperm tissue.
This tissue becomes the food the young plant will consume until the roots have developed after germination. After fertilization the ovules develop into the seeds; the ovule consists of a number of components: The funicle or seed stalk which attaches the ovule to the placenta and hence ovary or fruit wall, at the pericarp. The nucellus, the remnant of the megasporangium and main region of the ovule where the megagametophyte develops; the micropyle, a small pore or opening in the apex of the integument of the ovule where the pollen tube enters during the process of fertilization. The chalaza, the base of the ovule opposite the micropyle, where integument and nucellus are joined together; the shape of the ovules as they develop affects the final shape of the seeds. Plants produce ovules of four shapes: the most common shape is called anatropous, with a curved shape. Orthotropous ovules are straight with all the parts of the ovule lined up in a long row producing an uncurved seed. Campylotropous ovules have a curved megagametophyte giving the seed a tight "C" shape.
The last ovule shape is called amphitropous, where the ovule is inverted and turned back 90 degrees on its stalk. In the majority of flowering plants, the zygote's first division is transversely oriented in regards to the long axis, this establishes the polarity of the embryo; the upper or chalazal pole becomes the main area of growth of the embryo, while the lower or micropylar pole produces the stalk-like suspensor that attaches to the micropyle. The suspensor absorbs and manufactures nutrients from the endosperm that are used during the embryo's growth; the main components of the embryo are: The cotyledons, the seed leaves, attached to the embryonic axis. There may be two; the cotyledons are the source of nutrients in the non-endospermic dicotyledons, in which case they replace the endosperm, are thick and leathery. In endospermic seeds the cotyledons are papery. Dicotyledons have the point of attachment opposite one another on the axis; the epicotyl, the embryonic axis above the point of attachment of the cotyledon.
The plumule, the tip of the epicotyl, has a feathery appearance due to the presence of young leaf primordia at the apex, will become the shoot upon germination. The hypocotyl, the embryonic axis below the point of attachment of the cotyledon, connecting the epicotyl and the radicle, being the stem-root transition zone; the radicle, the basal tip of the hy