Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines, shrubs. Bark is a nontechnical term, it consists of the inner bark and the outer bark. The inner bark, which in older stems is living tissue, includes the innermost area of the periderm; the outer bark in older stems includes the dead tissue on the surface of the stems, along with parts of the innermost periderm and all the tissues on the outer side of the periderm. The outer bark on trees which lies external to the last formed periderm is called the rhytidome. Products derived from bark include: bark shingle siding and wall coverings and other flavorings, tanbark for tannin, latex, poisons, various hallucinogenic chemicals and cork. Bark has been used to make cloth and ropes and used as a surface for paintings and map making. A number of plants are grown for their attractive or interesting bark colorations and surface textures or their bark is used as landscape mulch. What is called bark includes a number of different tissues.
Cork is an external, secondary tissue, impermeable to water and gases, is called the phellem. The cork is produced by the cork cambium, a layer of meristematically active cells which serve as a lateral meristem for the periderm; the cork cambium, called the phellogen, is only one cell layer thick and it divides periclinally to the outside producing cork. The phelloderm, not always present in all barks, is a layer of cells formed by and interior to the cork cambium. Together, the phellem and phelloderm constitute the periderm. Cork cell walls contain suberin, a waxy substance which protects the stem against water loss, the invasion of insects into the stem, prevents infections by bacteria and fungal spores; the cambium tissues, i.e. the cork cambium and the vascular cambium, are the only parts of a woody stem where cell division occurs. Phloem is a nutrient-conducting tissue composed of sieve tubes or sieve cells mixed with parenchyma and fibers; the cortex is the primary tissue of roots. In stems the cortex is between the epidermis layer and the phloem, in roots the inner layer is not phloem but the pericycle.
From the outside to the inside of a mature woody stem, the layers include: Bark Periderm Cork, includes the rhytidome Cork cambium Phelloderm Cortex Phloem Vascular cambium Wood Sapwood Heartwood Pith In young stems, which lack what is called bark, the tissues are, from the outside to the inside: Epidermis, which may be replaced by periderm Cortex Primary and secondary phloem Vascular cambium Secondary and primary xylem. As the stem ages and grows, changes occur that transform the surface of the stem into the bark; the epidermis is a layer of cells that cover the plant body, including the stems, leaves and fruits, that protects the plant from the outside world. In old stems the epidermal layer and primary phloem become separated from the inner tissues by thicker formations of cork. Due to the thickening cork layer these cells die; this dead layer is the rough corky bark that forms around other stems. A secondary covering called the periderm forms on small woody stems and many non-woody plants, composed of cork, the cork cambium, the phelloderm.
The periderm forms from the phellogen. The periderm replaces the epidermis, acts as a protective covering like the epidermis. Mature phellem cells have suberin in their walls to protect the stem from desiccation and pathogen attack. Older phellem cells are dead; the skin on the potato tuber constitutes the cork of the periderm. In woody plants the epidermis of newly grown stems is replaced by the periderm in the year; as the stems grow a layer of cells form under the epidermis, called the cork cambium, these cells produce cork cells that turn into cork. A limited number of cell layers may form interior to the cork cambium, called the phelloderm; as the stem grows, the cork cambium produces new layers of cork which are impermeable to gases and water and the cells outside the periderm, namely the epidermis and older secondary phloem die. Within the periderm are lenticels, which form during the production of the first periderm layer. Since there are living cells within the cambium layers that need to exchange gases during metabolism, these lenticels, because they have numerous intercellular spaces, allow gaseous exchange with the outside atmosphere.
As the bark develops, new lenticels are formed within the cracks of the cork layers. The rhytidome is the most familiar part of bark, being the outer layer that covers the trunks of trees, it is composed of dead cells and is produced by the formation of multiple layers of suberized periderm and phloem tissue. The rhytidome is well developed in older stems and roots of trees. In shrubs, older bark is exfoliated and thick rhytidome accumulates, it is thickest and most distinctive at the trunk or bole of the tree. Bark tissues make up by weight between 10–20% of woody vascular plants and consists of various biopolymers, lignin, suberin and polysaccharides. Up to 40% of the bark tissue is made of lignin which forms an important part of a plant providing stru
Flax known as common flax or linseed, is a member of the genus Linum in the family Linaceae. It is a fiber crop cultivated in cooler regions of the world; the textiles made from flax are known in the Western countries as linen, traditionally used for bed sheets and table linen. The oil is known as linseed oil. In addition to referring to the plant itself, the word "flax" may refer to the unspun fibers of the flax plant; the plant species is known only as a cultivated plant, appears to have been domesticated just once from the wild species Linum bienne, called pale flax. Several other species in the genus Linum are similar in appearance to L. usitatissimum, cultivated flax, including some that have similar blue flowers, others with white, yellow, or red flowers. Some of these are perennial plants, unlike L. usitatissimum, an annual plant. Cultivated flax plants grow to 1.2 m tall, with slender stems. The leaves are glaucous green, slender lanceolate, 20–40 mm long, 3 mm broad; the flowers are 15 -- 25 mm in diameter, with five petals.
The fruit is a round, dry capsule 5–9 mm in diameter, containing several glossy brown seeds shaped like an apple pip, 4–7 mm long. The earliest evidence of humans using wild flax as a textile comes from the present-day Republic of Georgia, where spun and knotted wild flax fibers were found in Dzudzuana Cave and dated to the Upper Paleolithic, 30,000 years ago. Flax was first domesticated in the Fertile Crescent region. Evidence exists of a domesticated oilseed flax with increased seed size by 9,000 years ago from Tell Ramad in Syria. Use of the crop spread, reaching as far as Switzerland and Germany by 5,000 years ago. In China and India, domesticated flax was cultivated at least 5,000 years ago. Flax was cultivated extensively in ancient Egypt, where the temple walls had paintings of flowering flax, mummies were entombed in linen. Egyptian priests wore only linen. Phoenicians traded Egyptian linen throughout the Mediterranean and the Romans used it for their sails; as the Roman Empire declined, so did flax production, but Charlemagne revived the crop in the eighth century CE with laws designed to publicize the hygiene of linen textiles and the health of linseed oil.
Flanders became the major center of the linen industry in the European Middle Ages. In North America, flax was introduced by the colonists and it flourished there, but by the early 20th century, cheap cotton and rising farm wages had caused production of flax to become concentrated in northern Russia, which came to provide 90% of the world's output. Since flax has lost its importance as a commercial crop, due to the easy availability of more durable fibres. Flax is grown for its seeds, which can be ground into a meal or turned into linseed oil, a product used as a nutritional supplement and as an ingredient in many wood-finishing products. Flax is grown as an ornamental plant in gardens. Moreover, flax fibers are used to make linen; the specific epithet, means "most useful". Flax fibers taken from the stem of the plant are two to three times as strong as cotton fibers. Additionally, flax fibers are smooth and straight. Europe and North America both depended on flax for plant-based cloth until the 19th century, when cotton overtook flax as the most common plant for making rag-based paper.
Flax is grown on the Canadian prairies for linseed oil, used as a drying oil in paints and varnishes and in products such as linoleum and printing inks. Linseed meal, the byproduct of producing linseed oil from flax seeds, is used to feed livestock, it is a protein-rich feed for ruminants and fish. Flaxseeds occur in two basic varieties/colors: brown or yellow. Most types of these basic varieties have similar nutritional characteristics and equal numbers of short-chain omega-3 fatty acids; the exception is a type of yellow flax called solin, which has a different oil profile and is low in omega-3s. Flaxseeds produce a vegetable oil known as flaxseed oil or linseed oil, one of the oldest commercial oils, it is an edible oil sometimes followed by solvent extraction. Solvent-processed flaxseed oil has been used for many centuries as a drying oil in painting and varnishing. Although brown flaxseed varieties may be consumed as as the yellow ones, have been for thousands of years, its better-known uses are in paints, for fiber, for cattle feed.
A 100-gram portion of ground flaxseed supplies about 534 calories, 41 g of fat, 28 g of fiber, 20 g of protein. Flaxseed sprouts are edible and have a spicy flavor profile. Excessive consumption of flaxseeds with inadequate amounts of water may cause bowel obstruction. In northern India, called tisi or alsi, is traditionally roasted and eaten with boiled rice, a little water, a little salt. In India, linseed oil is known as javas in Marathi, it is used in Savji curries, such as mutton curries. Whole flaxseeds are chemically stable, but ground flaxseed meal, because of oxidation, may go rancid when left exposed to air at room temperature in as little as one week. Refrigeration and storage in sealed containers will keep ground flaxseed meal for a longer period before it turns rancid. Under conditions similar to those found in commercial bakeries, trained sensory panelists could not detect differences between bread made with freshly ground flaxseed and bread made with flaxseed, milled four months earlier and stored at room temperature.
This shows, if packed without exposure to air and light, milled flaxseed is stable against
The ribosome is a complex molecular machine, found within all living cells, that serves as the site of biological protein synthesis. Ribosomes link amino acids together in the order specified by messenger RNA molecules. Ribosomes consist of two major components: the small ribosomal subunits, which read the RNA, the large subunits, which join amino acids to form a polypeptide chain; each subunit consists of a variety of ribosomal proteins. The ribosomes and associated molecules are known as the translational apparatus; the sequence of DNA, which encodes the sequence of the amino acids in a protein, is copied into a messenger RNA chain. It may be copied many times into RNA chains. Ribosomes can bind to a messenger RNA chain and use its sequence for determining the correct sequence of amino acids for generating a given protein. Amino acids are selected and carried to the ribosome by transfer RNA molecules, which enter one part of the ribosome and bind to the messenger RNA chain, it is during this binding that the correct translation of nucleic acid sequence to amino acid sequence occurs.
For each coding triplet in the messenger RNA there is a distinct transfer RNA that matches and which carries the correct amino acid for that coding triplet. The attached amino acids are linked together by another part of the ribosome. Once the protein is produced, it can fold to produce a specific functional three-dimensional structure although during synthesis some proteins start folding into their correct form. A ribosome is therefore a ribonucleoprotein; each ribosome is divided into two subunits: a smaller subunit which binds to a larger subunit and the mRNA pattern, a larger subunit which binds to the tRNA, the amino acids, the smaller subunit. When a ribosome finishes reading an mRNA molecule, these two subunits split apart. Ribosomes are ribozymes, because the catalytic peptidyl transferase activity that links amino acids together is performed by the ribosomal RNA. Ribosomes are associated with the intracellular membranes that make up the rough endoplasmic reticulum. Ribosomes from bacteria and eukaryotes in the three-domain system, resemble each other to a remarkable degree, evidence of a common origin.
They differ in their size, sequence and the ratio of protein to RNA. The differences in structure allow some antibiotics to kill bacteria by inhibiting their ribosomes, while leaving human ribosomes unaffected. In bacteria and archaea, more than one ribosome may move along a single mRNA chain at one time, each "reading" its sequence and producing a corresponding protein molecule; the mitochondrial ribosomes of eukaryotic cells, are produced from mitochondrial genes, functionally resemble many features of those in bacteria, reflecting the evolutionary origin of mitochondria. Ribosomes were first observed in the mid-1950s by Romanian-American cell biologist George Emil Palade, using an electron microscope, as dense particles or granules; the term "ribosome" was proposed by scientist Richard B. Roberts in the end of 1950s: During the course of the symposium a semantic difficulty became apparent. To some of the participants, "microsomes" mean the ribonucleoprotein particles of the microsome fraction contaminated by other protein and lipid material.
The phrase "microsomal particles" does not seem adequate, "ribonucleoprotein particles of the microsome fraction" is much too awkward. During the meeting, the word "ribosome" was suggested, which has a satisfactory name and a pleasant sound; the present confusion would be eliminated if "ribosome" were adopted to designate ribonucleoprotein particles in sizes ranging from 35 to 100S. Albert Claude, Christian de Duve, George Emil Palade were jointly awarded the Nobel Prize in Physiology or Medicine, in 1974, for the discovery of the ribosome; the Nobel Prize in Chemistry 2009 was awarded to Venkatraman Ramakrishnan, Thomas A. Steitz and Ada E. Yonath for determining the detailed structure and mechanism of the ribosome; the ribosome is a complex cellular machine. It is made up of specialized RNA known as ribosomal RNA as well as dozens of distinct proteins; the ribosomal proteins and rRNAs are arranged into two distinct ribosomal pieces of different size, known as the large and small subunit of the ribosome.
Ribosomes consist of two subunits that fit together and work as one to translate the mRNA into a polypeptide chain during protein synthesis. Because they are formed from two subunits of non-equal size, they are longer in the axis than in diameter. Prokaryotic ribosomes are around 20 nm in diameter and are composed of 65% rRNA and 35% ribosomal proteins. Eukaryotic ribosomes are between 25 and 30 nm in diameter with an rRNA-to-protein ratio, close to 1. Crystallographic work has shown that there are no ribosomal proteins close to the reaction site for polypeptide synthesis; this suggests that the protein components of ribosomes do not directly participate in peptide bond formation catalysis, but rather that these proteins act as a scaffold that may enhance the ability of rRNA to synthesize protein. The ribosomal subunits of prokaryotes and eukaryotes are quite similar; the unit of measurement used to describe the ribosomal subunits and the rRNA fragments is the Svedberg unit, a measure of the rate of sedimentation in centrifugation rather than size.
This accounts for why fragment names do not add up: for example, prokaryotic 70S ribosomes are made of 50S and 30S subunits. Prokaryotes have 70
Sucrose is common sugar. It is a molecule composed of two monosaccharides: glucose and fructose. Sucrose is produced in plants, from which table sugar is refined, it has the molecular formula C12H22O11. For human consumption, sucrose is extracted, refined, from either sugar cane or sugar beet. Sugar mills are located where sugarcane is grown to crush the cane and produce raw sugar, shipped around the world for refining into pure sucrose; some sugar mills process the raw sugar into pure sucrose. Sugar beet factories are located in colder climates where the beet is grown and process the beets directly into refined sugar; the sugar refining process involves washing the raw sugar crystals before dissolving them into a sugar syrup, filtered and passed over carbon to remove any residual colour. The by-now clear sugar syrup is concentrated by boiling under a vacuum and crystallized as the final purification process to produce crystals of pure sucrose; these crystals are clear and have a sweet taste. En masse, the crystals appear white.
Sugar is an added ingredient in food production and food recipes. About 185 million tonnes of sugar were produced worldwide in 2017; the word sucrose was coined in 1857 by the English chemist William Miller from the French sucre and the generic chemical suffix for sugars -ose. The abbreviated term Suc is used for sucrose in scientific literature; the name saccharose was coined in 1860 by the French chemist Marcellin Berthelot. Saccharose is an obsolete name for sugars in general sucrose. In sucrose, the components glucose and fructose are linked via an ether bond between C1 on the glucosyl subunit and C2 on the fructosyl unit; the bond is called a glycosidic linkage. Glucose exists predominantly as two isomeric "pyranoses", but only one of these forms links to the fructose. Fructose itself exists as a mixture of "furanoses", each of which having α and β isomers, but only one particular isomer links to the glucosyl unit. What is notable about sucrose is that, unlike most disaccharides, the glycosidic bond is formed between the reducing ends of both glucose and fructose, not between the reducing end of one and the nonreducing end of the other.
This linkage inhibits further bonding to other saccharide units. Since it contains no anomeric hydroxyl groups, it is classified as a non-reducing sugar. Sucrose crystallizes in the monoclinic space group P21 with room-temperature lattice parameters a = 1.08631 nm, b = 0.87044 nm, c = 0.77624 nm, β = 102.938°. The purity of sucrose is measured by polarimetry, through the rotation of plane-polarized light by a solution of sugar; the specific rotation at 20 °C using yellow "sodium-D" light is +66.47°. Commercial samples of sugar are assayed using this parameter. Sucrose does not deteriorate at ambient conditions. Sucrose does not melt at high temperatures. Instead, it decomposes at 186 °C to form caramel. Like other carbohydrates, it combusts to carbon water. Mixing sucrose with the oxidizer potassium nitrate produces the fuel known as rocket candy, used to propel amateur rocket motors. C12H22O11 + 6 KNO3 → 9 CO + 3 N2 + 11 H2O + 3 K2CO3This reaction is somewhat simplified though; some of the carbon does get oxidized to carbon dioxide, other reactions, such as the water-gas shift reaction take place.
A more accurate theoretical equation is: C12H22O11 + 6.288 KNO3 → 3.796 CO2 + 5.205 CO + 7.794 H2O + 3.065 H2 + 3.143 N2 + 2.998 K2CO3 + 0.274 KOH Sucrose burns with chloric acid, formed by the reaction of hydrochloric acid and potassium chlorate: 8 HClO3 + C12H22O11 → 11 H2O + 12 CO2 + 8 HClSucrose can be dehydrated with sulfuric acid to form a black, carbon-rich solid, as indicated in the following idealized equation: H2SO4 + C12H22O11 → 12 C + 11 H2O + Heat. The formula for sucrose's decomposition can be represented as a two-step reaction: the first simplified reaction is dehydration of sucrose to pure carbon and water, carbon oxidises to CO2 with O2 from air. C12H22O11 + heat → 12 C + 11 H2O 12 C + 12 O2 → 12 CO2 Hydrolysis breaks the glycosidic bond converting sucrose into glucose and fructose. Hydrolysis is, however, so slow. If the enzyme sucrase is added, the reaction will proceed rapidly. Hydrolysis can be accelerated with acids, such as cream of tartar or lemon juice, both weak acids.
Gastric acidity converts sucrose to glucose and fructose during digestion, the bond between them being an acetal bond which can be broken by an acid. Given heats of combustion of 1349.6 kcal/mol for sucrose, 673.0 for glucose, 675.6 for fructose, hydrolysis releases about 1.0 kcal per mole of sucrose, or about 3 small calories per gram of product. The biosynthesis of sucrose proceeds via the precursors UDP-glucose and fructose 6-phosphate, catalyzed by the enzyme sucrose-6-phosphate synthase; the energy for the reaction is gained by the cleavage of uridine diphosphate. Sucrose is formed by plants and cyanobacteria but not by other organisms. Sucrose is found in many food plants along with the monosaccharide fructose. In many fruits, such as pineapple and apricot, sucrose is the main sugar. In others, such as grapes and pears, fructose is the main sugar. Although sucrose is invariably isolated from natural sources, its chemical synthesis was first achieved in 1953 by Raymond Lemieux. In nature, sucrose is present in many plants, in particular their roots and nectars, because it serves as a way to store energy from photosynthesis.
Many mammals, birds and bacteria accumulate and feed on the sucrose in plants and for some it is their main food sou
Fiber or fibre is a natural or synthetic substance, longer than it is wide. Fibers are used in the manufacture of other materials; the strongest engineering materials incorporate fibers, for example carbon fiber and ultra-high-molecular-weight polyethylene. Synthetic fibers can be produced cheaply and in large amounts compared to natural fibers, but for clothing natural fibers can give some benefits, such as comfort, over their synthetic counterparts. Natural fibers develop or occur in the fiber shape, include those produced by plants and geological processes, they can be classified according to their origin: Vegetable fibers are based on arrangements of cellulose with lignin: examples include cotton, jute, ramie, sisal and banana. Plant fibers are employed in the manufacture of paper and textile, dietary fiber is an important component of human nutrition. Wood fiber, distinguished from vegetable fiber, is from tree sources. Forms include groundwood, thermomechanical pulp, bleached or unbleached kraft or sulfite pulps.
Kraft and sulfite refer to the type of pulping process used to remove the lignin bonding the original wood structure, thus freeing the fibers for use in paper and engineered wood products such as fiberboard. Animal fibers consist of particular proteins. Instances are silkworm silk, spider silk, catgut, sea silk and hair such as cashmere wool and angora, fur such as sheepskin, mink, beaver, etc. Mineral fibers include the asbestos group. Asbestos is the only occurring long mineral fiber. Six minerals have been classified as "asbestos" including chrysotile of the serpentine class and those belonging to the amphibole class: amosite, tremolite and actinolite. Short, fiber-like minerals include palygorskite. Biological fibers known as fibrous proteins or protein filaments consist of biologically relevant and biologically important proteins, mutations or other genetic defects can lead to severe diseases. Instances are collagen family of proteins, muscle proteins like actin, cell proteins like microtubules and many others, spider silk and hair etc.
Human-made or chemical fibers are fibers whose chemical composition and properties are modified during the manufacturing process. Man-made fibers consist of synthetic fibers. Semi-synthetic fibers are made from raw materials with long-chain polymer structure and are only modified and degraded by chemical processes, in contrast to synthetic fibers such as nylon or dacron, which the chemist synthesizes from low-molecular weight compounds by polymerization reactions; the earliest semi-synthetic fiber is rayon. Most semi-synthetic fibers are cellulose regenerated fibers. Cellulose fibers are a subset of man-made fibers, regenerated from natural cellulose; the cellulose comes from various sources: rayon from tree wood fiber, Modal from beech trees, bamboo fiber from bamboo, seacell from seaweed, etc. In the production of these fibers, the cellulose is reduced to a pure form as a viscous mass and formed into fibers by extrusion through spinnerets. Therefore, the manufacturing process leaves few characteristics distinctive of the natural source material in the finished products.
Some examples of this fiber type are: rayon bamboo fiber Lyocell, a brand of rayon Modal, using beech trees as input diacetate fiber triacetate fiber. Cellulose diacetate and -triacetate were classified under the term rayon, but are now considered distinct materials. Synthetic come from synthetic materials such as petrochemicals, unlike those man-made fibers derived from such natural substances as cellulose or protein. Fiber classification in reinforced plastics falls into two classes: short fibers known as discontinuous fibers, with a general aspect ratio between 20 and 60, long fibers known as continuous fibers, the general aspect ratio is between 200 and 500. Metallic fibers can be drawn from ductile metals such as copper, gold or silver and extruded or deposited from more brittle ones, such as nickel, aluminum or iron. See Stainless steel fibers. Carbon fibers are based on oxidized and via pyrolysis carbonized polymers like PAN, but the end product is pure carbon. Silicon carbide fibers, where the basic polymers are not hydrocarbons but polymers, where about 50% of the carbon atoms are replaced by silicon atoms, so-called poly-carbo-silanes.
The pyrolysis yields an amorphous silicon carbide, including other elements like oxygen, titanium, or aluminium, but with mechanical properties similar to those of carbon fibers. Fiberglass, made from specific glass, optical fiber, made from purified natural quartz, are man-made fibers that come from natural raw materials, silica fiber, made from sodium silicate and basalt fiber made from melted basalt. Mineral fibers can be strong because they are formed with a low number of surface defects, asbestos is a common one. Polymer fibers are a subset of man-made fibers, which are based on synthetic chemicals rather than arising from natural materials by a purely physical process; these fibers are made from: polyamide nylon PET or PBT polyester phenol-formaldehyde polyvinyl chloride fiber vinyon polyolefins olefin fiber acrylic polyesters, pure polyester PAN fibers are used to make carbon fiber by roasting them in a low oxygen enviro
In botany, a fruit is the seed-bearing structure in flowering plants formed from the ovary after flowering. Fruits are the means. Edible fruits, in particular, have propagated with the movements of humans and animals in a symbiotic relationship as a means for seed dispersal and nutrition. Accordingly, fruits account for a substantial fraction of the world's agricultural output, some have acquired extensive cultural and symbolic meanings. In common language usage, "fruit" means the fleshy seed-associated structures of a plant that are sweet or sour, edible in the raw state, such as apples, grapes, lemons and strawberries. On the other hand, in botanical usage, "fruit" includes many structures that are not called "fruits", such as bean pods, corn kernels and wheat grains; the section of a fungus that produces spores is called a fruiting body. Many common terms for seeds and fruit do not correspond to the botanical classifications. In culinary terminology, a fruit is any sweet-tasting plant part a botanical fruit.
However, in botany, a fruit is the ripened ovary or carpel that contains seeds, a nut is a type of fruit and not a seed, a seed is a ripened ovule. Examples of culinary "vegetables" and nuts that are botanically fruit include corn, eggplant, sweet pepper, tomato. In addition, some spices, such as allspice and chili pepper, are fruits. In contrast, rhubarb is referred to as a fruit, because it is used to make sweet desserts such as pies, though only the petiole of the rhubarb plant is edible, edible gymnosperm seeds are given fruit names, e.g. ginkgo nuts and pine nuts. Botanically, a cereal grain, such as corn, rice, or wheat, is a kind of fruit, termed a caryopsis. However, the fruit wall is thin and is fused to the seed coat, so all of the edible grain is a seed; the outer edible layer, is the pericarp, formed from the ovary and surrounding the seeds, although in some species other tissues contribute to or form the edible portion. The pericarp may be described in three layers from outer to inner, the epicarp and endocarp.
Fruit that bears a prominent pointed terminal projection is said to be beaked. A fruit results from maturation of one or more flowers, the gynoecium of the flower forms all or part of the fruit. Inside the ovary/ovaries are one or more ovules where the megagametophyte contains the egg cell. After double fertilization, these ovules will become seeds; the ovules are fertilized in a process that starts with pollination, which involves the movement of pollen from the stamens to the stigma of flowers. After pollination, a tube grows from the pollen through the stigma into the ovary to the ovule and two sperm are transferred from the pollen to the megagametophyte. Within the megagametophyte one of the two sperm unites with the egg, forming a zygote, the second sperm enters the central cell forming the endosperm mother cell, which completes the double fertilization process; the zygote will give rise to the embryo of the seed, the endosperm mother cell will give rise to endosperm, a nutritive tissue used by the embryo.
As the ovules develop into seeds, the ovary begins to ripen and the ovary wall, the pericarp, may become fleshy, or form a hard outer covering. In some multiseeded fruits, the extent to which the flesh develops is proportional to the number of fertilized ovules; the pericarp is differentiated into two or three distinct layers called the exocarp and endocarp. In some fruits simple fruits derived from an inferior ovary, other parts of the flower, fuse with the ovary and ripen with it. In other cases, the sepals, petals and/or stamens and style of the flower fall off; when such other floral parts are a significant part of the fruit, it is called an accessory fruit. Since other parts of the flower may contribute to the structure of the fruit, it is important to study flower structure to understand how a particular fruit forms. There are three general modes of fruit development: Apocarpous fruits develop from a single flower having one or more separate carpels, they are the simplest fruits. Syncarpous fruits develop from a single gynoecium having two or more carpels fused together.
Multiple fruits form from many different flowers. Plant scientists have grouped fruits into three main groups, simple fruits, aggregate fruits, composite or multiple fruits; the groupings are not evolutionarily relevant, since many diverse plant taxa may be in the same group, but reflect how the flower organs are arranged and how the fruits develop. Simple fruits can be either dry or fleshy, result from the ripening of a simple or compound ovary in a flower with only one pistil. Dry fruits may be either dehiscent, or indehiscent. Types of dry, simple fruits, examples of each, include: achene – most seen in aggregate fruits capsule – caryopsis – cypsela – an achene-like fruit derived from the individual florets in a capitulum. Fibrous drupe – follicle – is formed from a single carpel, opens by one suture
Sap is a fluid transported in xylem cells or phloem sieve tube elements of a plant. These cells transport water and nutrients throughout the plant. Sap is distinct from resin, or cell sap. Saps may be broadly divided into two types: xylem sap and phloem sap. Xylem sap consists of a watery solution of hormones, mineral elements and other nutrients. Transport of sap in xylem is characterized by movement from the roots toward the leaves. Over the past century, there has been some controversy regarding the mechanism of xylem sap transport. Xylem sap transport can be disrupted by cavitation—an "abrupt phase change from liquid to vapor"—resulting in air-filled xylem conduits. In addition to being a fundamental physical limit on tree height, two environmental stresses can disrupt xylem transport by cavitation: "increasingly negative xylem pressures associated with water stress, freeze-thaw cycles in temperate climates. Phloem sap consists of sugars and mineral elements dissolved in water, it flows from where carbohydrates are stored to where they are used.
The pressure flow hypothesis proposes a mechanism for phloem sap transport. Although other hypotheses have been proposed. Phloem sap is thought to play a role in sending informational signals throughout vascular plants. "Loading and unloading patterns are determined by the conductivity and number of plasmodesmata and the position-dependent function of solute-specific, plasma membrane transport proteins. Recent evidence indicates that mobile proteins and RNA are part of the plant's long-distance communication signaling system. Evidence exists for the directed transport and sorting of macromolecules as they pass through plasmodesmata." A large number of insects of the order Hemiptera, feed directly on phloem sap, make it the primary component of their diet. Phloem sap is "nutrient-rich compared with many other plant products and lacking in toxins and feeding deterrents, it is consumed as the dominant or sole diet by a restricted range of animals"; this apparent paradox is explained by the fact that phloem sap is physiologically extreme in terms of animal digestion, it is hypothesized that few animals take direct advantage of this because they lack two adaptations that are necessary to enable direct use by animals.
These include the existence of a high ratio of non-essential/essential amino acids in phloem sap for which these adapted Hemiptera insects contain symbiotic microorganisms which can provide them with essential amino acids. A much larger set of animals do however consume phloem sap by proxy, either "through feeding on the honeydew of phloem-feeding hemipterans. Honeydew is physiologically less extreme than phloem sap, with a higher essential:non-essential amino acid ratio and lower osmotic pressure," or by feeding on the biomass of insects that have grown on more direct ingestion of phloem sap. Maple syrup is made from reduced sugar maple xylem sap; the sap is harvested from the Sugar Maple, Acer saccharum. In some countries harvesting the early spring sap of birch trees for human consumption is common practice. Certain palm tree sap can be used to make palm syrup. In the Canary Islands they use the Canary Island Date Palm while in Chile they use the Chilean Wine Palm to make their syrup called miel de palma.