77-605: [REDACTED] Look up arabica in Wiktionary, the free dictionary. Arabica may refer to: Food and drink [ edit ] Coffea arabica , the tree species coffee is most often produced from Revalenta arabica , an 18th century diet for invalids Language [ edit ] Arebica , the Bosnian Arabic alphabet Belarusian Arabic alphabet Publications [ edit ] Arabica (journal) ,
154-463: A drupe (commonly called a "cherry") 10–15 mm in diameter, maturing bright red to purple and typically containing two seeds , often called coffee beans. Endemic to the southwestern highlands of Ethiopia , Coffea arabica is grown in dozens of countries between the Tropic of Capricorn and the Tropic of Cancer . It is commonly used as an understory shrub. It has also been recovered from
231-408: A decussate pattern, in which each node rotates by 1/4 (90°) as in the herb basil . The leaves of tricussate plants such as Nerium oleander form a triple helix. The leaves of some plants do not form helices. In some plants, the divergence angle changes as the plant grows. In orixate phyllotaxis, named after Orixa japonica , the divergence angle is not constant. Instead, it is periodic and follows
308-682: A huge wild population of 13.5 to 19.5 billion individuals throughout its native range, C. arabica is still considered endangered on the IUCN Red List due to numerous threats it faces. Due to being an understory plant, it requires standing forest, making it highly susceptible to the historically significant deforestation levels in Ethiopia; prior to major deforestation, forest cover was thought to be between 25–31% of Ethiopia's total land surface, but has dropped to just 4%, and deforestation still continues. In addition, climate change may have
385-475: A journal of Arabic and Islamic studies Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Arabica . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Arabica&oldid=1203727843 " Category : Disambiguation pages Hidden categories: Short description
462-527: A major effect on growing areas for wild C. arabica in Ethiopia due to its high-temperature sensitivity, and estimates indicate that population could reduce by 50–80% with a 40–50% reduction in area of occupancy by 2088; climate change can also impact reproductive success. In addition, the main pest of coffee, the coffee berry borer ( Hypothenemus hampei ) may benefit from climate change and colonize higher altitudes that were formerly too cold for it, which can also impact coffee populations. The conservation of
539-515: A petiole like structure. Pseudopetioles occur in some monocotyledons including bananas , palms and bamboos . Stipules may be conspicuous (e.g. beans and roses ), soon falling or otherwise not obvious as in Moraceae or absent altogether as in the Magnoliaceae . A petiole may be absent (apetiolate), or the blade may not be laminar (flattened). The petiole mechanically links the leaf to
616-463: A plant matures; as a case in point Eucalyptus species commonly have isobilateral, pendent leaves when mature and dominating their neighbors; however, such trees tend to have erect or horizontal dorsiventral leaves as seedlings, when their growth is limited by the available light. Other factors include the need to balance water loss at high temperature and low humidity against the need to absorb atmospheric carbon dioxide. In most plants, leaves also are
693-508: A problematic invasive species. Coffee has been produced in Queensland and New South Wales of Australia, starting in the 1980s and 1990s. The Wet Tropics Management Authority has classified Coffea arabica as an environmental weed for southeast Queensland due to its invasiveness in non-agricultural areas. The first written record of coffee made from roasted coffee beans (botanical seeds) comes from Arab scholars, who wrote that it
770-419: A regular organization at the cellular scale. Specialized cells that differ markedly from surrounding cells, and which often synthesize specialized products such as crystals, are termed idioblasts . The epidermis is the outer layer of cells covering the leaf. It is covered with a waxy cuticle which is impermeable to liquid water and water vapor and forms the boundary separating the plant's inner cells from
847-475: A scaffolding matrix imparting mechanical rigidity to leaves. Leaves are normally extensively vascularized and typically have networks of vascular bundles containing xylem , which supplies water for photosynthesis , and phloem , which transports the sugars produced by photosynthesis. Many leaves are covered in trichomes (small hairs) which have diverse structures and functions. The major tissue systems present are These three tissue systems typically form
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#1732772107155924-541: A severe dry season, some plants may shed their leaves until the dry season ends. In either case, the shed leaves may be expected to contribute their retained nutrients to the soil where they fall. In contrast, many other non-seasonal plants, such as palms and conifers, retain their leaves for long periods; Welwitschia retains its two main leaves throughout a lifetime that may exceed a thousand years. The leaf-like organs of bryophytes (e.g., mosses and liverworts ), known as phyllids , differ heavily morphologically from
1001-481: A sign of quality. In 2023, several large coffee roasters dropped the "100% Arabica" declaration previously residing on some of their packages and started to blend less expensive Robusta coffee into the mix. To avoid making larger changes to the visual design of the package the Arabica label was replaced by other labeling, keeping the previous ornamental design, thereby presenting a case of shrinkflation . In some case,
1078-402: A single (sometimes more) primary vein in the centre of the leaf, referred to as the midrib or costa, which is continuous with the vasculature of the petiole. The secondary veins, also known as second order veins or lateral veins, branch off from the midrib and extend toward the leaf margins. These often terminate in a hydathode , a secretory organ, at the margin. In turn, smaller veins branch from
1155-578: A single leaf grows from each node, and when the stem is held straight, the leaves form a helix . The divergence angle is often represented as a fraction of a full rotation around the stem. A rotation fraction of 1/2 (a divergence angle of 180°) produces an alternate arrangement, such as in Gasteria or the fan-aloe Kumara plicatilis . Rotation fractions of 1/3 (divergence angles of 120°) occur in beech and hazel . Oak and apricot rotate by 2/5, sunflowers, poplar, and pear by 3/8, and in willow and almond
1232-533: A single point. In evolutionary terms, early emerging taxa tend to have dichotomous branching with reticulate systems emerging later. Veins appeared in the Permian period (299–252 mya), prior to the appearance of angiosperms in the Triassic (252–201 mya), during which vein hierarchy appeared enabling higher function, larger leaf size and adaption to a wider variety of climatic conditions. Although it
1309-409: A small leaf. Stipules may be lasting and not be shed (a stipulate leaf, such as in roses and beans ), or be shed as the leaf expands, leaving a stipule scar on the twig (an exstipulate leaf). The situation, arrangement, and structure of the stipules is called the "stipulation". Veins (sometimes referred to as nerves) constitute one of the most visible features of leaves. The veins in a leaf represent
1386-405: A specialized cell group known as the stomatal complex. The opening and closing of the stomatal aperture is controlled by the stomatal complex and regulates the exchange of gases and water vapor between the outside air and the interior of the leaf. Stomata therefore play the important role in allowing photosynthesis without letting the leaf dry out. In a typical leaf, the stomata are more numerous over
1463-483: A variety of patterns (venation) and form cylindrical bundles, usually lying in the median plane of the mesophyll , between the two layers of epidermis . This pattern is often specific to taxa, and of which angiosperms possess two main types, parallel and reticulate (net like). In general, parallel venation is typical of monocots, while reticulate is more typical of eudicots and magnoliids (" dicots "), though there are many exceptions. The vein or veins entering
1540-460: Is called a stipe in ferns . The lamina is the expanded, flat component of the leaf which contains the chloroplasts . The sheath is a structure, typically at the base that fully or partially clasps the stem above the node, where the leaf is attached. Leaf sheathes typically occur in Poaceae (grasses) and Apiaceae (umbellifers). Between the sheath and the lamina, there may be a pseudopetiole ,
1617-524: Is different from Wikidata All article disambiguation pages All disambiguation pages Coffea arabica Coffea arabica ( / ə ˈ r æ b ɪ k ə / ), also known as the Arabica coffee , is a species of flowering plant in the coffee and madder family Rubiaceae . It is believed to be the first species of coffee to have been cultivated and is the dominant cultivar, representing about 60% of global production. Coffee produced from
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#17327721071551694-406: Is one of the polyploid species of the genus Coffea , as it carries 4 copies of the 11 chromosomes (44 total) instead of the 2 copies of diploid species. Specifically, Coffea arabica is itself the result of a hybridization between the diploids Coffea canephora and Coffea eugenioides , thus making it an allotetraploid , with two copies of two different genomes. This hybridization event at
1771-609: Is prevented by pruning the tree. The flowers only last a few days, leaving behind only the thick, dark-green leaves. The berries then begin to appear. These are as dark green as the foliage until they begin to ripen, at first to yellow and then light red and finally darkening to a glossy, deep red. At this point, they are called " cherries ", which fruit they then resemble, and are ready for picking. The berries are oblong and about 1 cm long. Inferior coffee results from picking them too early or too late, so many are picked by hand to be able to better select them, as they do not all ripen at
1848-406: Is the more complex pattern, branching veins appear to be plesiomorphic and in some form were present in ancient seed plants as long as 250 million years ago. A pseudo-reticulate venation that is actually a highly modified penniparallel one is an autapomorphy of some Melanthiaceae , which are monocots; e.g., Paris quadrifolia (True-lover's Knot). In leaves with reticulate venation, veins form
1925-577: The Boma Plateau in South Sudan . Coffea arabica is also found on Mount Marsabit in northern Kenya , but it is unclear whether this is a truly native or naturalised occurrence; recent studies support it being naturalised. The species is widely naturalised in areas outside its native land, in many parts of Africa , Latin America , Southeast Asia , India , China , and assorted islands in
2002-621: The Caribbean and in the Pacific . The coffee tree was first brought to Hawaii in 1813, and it began to be extensively grown by about 1850. It was formerly more widely grown, especially in Kona , and it persists after cultivation in many areas. In some valleys, it is a highly invasive weed. In the Udawattakele and Gannoruwa Forest Reserves near Kandy, Sri Lanka, coffee shrubs are also
2079-494: The diet of many animals . Correspondingly, leaves represent heavy investment on the part of the plants bearing them, and their retention or disposition are the subject of elaborate strategies for dealing with pest pressures, seasonal conditions, and protective measures such as the growth of thorns and the production of phytoliths , lignins , tannins and poisons . Deciduous plants in frigid or cold temperate regions typically shed their leaves in autumn, whereas in areas with
2156-424: The gymnosperms and angiosperms . Euphylls are also referred to as macrophylls or megaphylls (large leaves). A structurally complete leaf of an angiosperm consists of a petiole (leaf stalk), a lamina (leaf blade), stipules (small structures located to either side of the base of the petiole) and a sheath. Not every species produces leaves with all of these structural components. The proximal stalk or petiole
2233-551: The phyllids of mosses and liverworts . Leaves are the most important organs of most vascular plants. Green plants are autotrophic , meaning that they do not obtain food from other living things but instead create their own food by photosynthesis . They capture the energy in sunlight and use it to make simple sugars , such as glucose and sucrose , from carbon dioxide and water. The sugars are then stored as starch , further processed by chemical synthesis into more complex organic molecules such as proteins or cellulose ,
2310-399: The plant shoots and roots . Vascular plants transport sucrose in a special tissue called the phloem . The phloem and xylem are parallel to each other, but the transport of materials is usually in opposite directions. Within the leaf these vascular systems branch (ramify) to form veins which supply as much of the leaf as possible, ensuring that cells carrying out photosynthesis are close to
2387-453: The shoot system. In most leaves, the primary photosynthetic tissue is the palisade mesophyll and is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of Eucalyptus , palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Most leaves are flattened and have distinct upper ( adaxial ) and lower ( abaxial ) surfaces that differ in color, hairiness,
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2464-679: The amount of light they absorb to avoid or mitigate excessive heat, ultraviolet damage, or desiccation, or to sacrifice light-absorption efficiency in favor of protection from herbivory. For xerophytes the major constraint is not light flux or intensity , but drought. Some window plants such as Fenestraria species and some Haworthia species such as Haworthia tesselata and Haworthia truncata are examples of xerophytes. and Bulbine mesembryanthemoides . Leaves also function to store chemical energy and water (especially in succulents ) and may become specialized organs serving other functions, such as tendrils of peas and other legumes,
2541-583: The basic structural material in plant cell walls, or metabolized by cellular respiration to provide chemical energy to run cellular processes. The leaves draw water from the ground in the transpiration stream through a vascular conducting system known as xylem and obtain carbon dioxide from the atmosphere by diffusion through openings called stomata in the outer covering layer of the leaf ( epidermis ), while leaves are orientated to maximize their exposure to sunlight. Once sugar has been synthesized, it needs to be transported to areas of active growth such as
2618-418: The beans. The coffee beans are actually two seeds within the fruit; sometimes, a third seed or one seed, a peaberry , grows in the fruit at the tips of the branches. These seeds are covered in two membranes; the outer one is called the "parchment coat" and the inner one is called the "silver skin". On Java , trees are planted at all times of the year and are harvested year-round. In parts of Brazil , however,
2695-458: The blade attaches directly to the stem. Subpetiolate leaves are nearly petiolate or have an extremely short petiole and may appear to be sessile. In clasping or decurrent leaves, the blade partially surrounds the stem. When the leaf base completely surrounds the stem, the leaves are said to be perfoliate , such as in Eupatorium perfoliatum . In peltate leaves, the petiole attaches to
2772-406: The blade inside the blade margin. In some Acacia species, such as the koa tree ( Acacia koa ), the petioles are expanded or broadened and function like leaf blades; these are called phyllodes . There may or may not be normal pinnate leaves at the tip of the phyllode. A stipule , present on the leaves of many dicotyledons , is an appendage on each side at the base of the petiole, resembling
2849-412: The coffee growing on plantations around the world contains less than 1% of the diversity in the wilds of Yemen alone. Climate change also serves as a threat to cultivated C. arabica due to their temperature sensitivity, and some studies estimate that by 2050, over half of the land used for cultivating coffee could be unproductive. The more heat-tolerant Coffea stenophylla may replace C. arabica as
2926-478: The coffee is still advertised as "100% Arabica" in flyers in 2024, but is no longer declared so on the actual package. One strain of Coffea arabica (called AC1, AC2 and AC3 in honour of the geneticist Alcides Carvalho) naturally contains very little caffeine. While beans of normal C. arabica plants contain 12 mg of caffeine per gram of dry mass, these mutants contain only 0.76 mg of caffeine per gram, with similar expected cup quality. Although it has
3003-426: The dominant coffee species in cultivation in order to guard against this. [REDACTED] Coffee portal Leaf A leaf ( pl. : leaves ) is a principal appendage of the stem of a vascular plant , usually borne laterally above ground and specialized for photosynthesis . Leaves are collectively called foliage , as in "autumn foliage", while the leaves, stem, flower, and fruit collectively form
3080-606: The early Devonian lycopsid Baragwanathia , first evolved as enations, extensions of the stem. True leaves or euphylls of larger size and with more complex venation did not become widespread in other groups until the Devonian period , by which time the carbon dioxide concentration in the atmosphere had dropped significantly. This occurred independently in several separate lineages of vascular plants, in progymnosperms like Archaeopteris , in Sphenopsida , ferns and later in
3157-558: The equivalents of the petioles and stipules of leaves. Because each leaflet can appear to be a simple leaf, it is important to recognize where the petiole occurs to identify a compound leaf. Compound leaves are a characteristic of some families of higher plants, such as the Fabaceae . The middle vein of a compound leaf or a frond , when it is present, is called a rachis . Leaves which have a petiole (leaf stalk) are said to be petiolate . Sessile (epetiolate) leaves have no petiole and
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3234-657: The external world. The cuticle is in some cases thinner on the lower epidermis than on the upper epidermis, and is generally thicker on leaves from dry climates as compared with those from wet climates. The epidermis serves several functions: protection against water loss by way of transpiration , regulation of gas exchange and secretion of metabolic compounds. Most leaves show dorsoventral anatomy: The upper (adaxial) and lower (abaxial) surfaces have somewhat different construction and may serve different functions. The epidermis tissue includes several differentiated cell types; epidermal cells, epidermal hair cells ( trichomes ), cells in
3311-406: The fraction is 5/13. These arrangements are periodic. The denominator of the rotation fraction indicates the number of leaves in one period, while the numerator indicates the number of complete turns or gyres made in one period. For example: Most divergence angles are related to the sequence of Fibonacci numbers F n . This sequence begins 1, 1, 2, 3, 5, 8, 13; each term is the sum of
3388-492: The genetic variation of C. arabica relies on conserving healthy populations of wild coffee in the Afromontane rainforests of Yemen. Genetic research has shown coffee cultivation is threatening the genetic integrity of wild coffee because it exposes wild genotypes to cultivars . Nearly all of the coffee that has been cultivated over the past few centuries originated from just a handful of wild plants from Yemen, and
3465-866: The ground, they are referred to as prostrate . Perennial plants whose leaves are shed annually are said to have deciduous leaves, while leaves that remain through winter are evergreens . Leaves attached to stems by stalks (known as petioles ) are called petiolate, and if attached directly to the stem with no petiole they are called sessile. Dicot leaves have blades with pinnate venation (where major veins diverge from one large mid-vein and have smaller connecting networks between them). Less commonly, dicot leaf blades may have palmate venation (several large veins diverging from petiole to leaf edges). Finally, some exhibit parallel venation. Monocot leaves in temperate climates usually have narrow blades, and usually parallel venation converging at leaf tips or edges. Some also have pinnate venation. The arrangement of leaves on
3542-443: The leaf from the petiole are called primary or first-order veins. The veins branching from these are secondary or second-order veins. These primary and secondary veins are considered major veins or lower order veins, though some authors include third order. Each subsequent branching is sequentially numbered, and these are the higher order veins, each branching being associated with a narrower vein diameter. In parallel veined leaves,
3619-523: The leaf veins form, and these have functional implications. Of these, angiosperms have the greatest diversity. Within these the major veins function as the support and distribution network for leaves and are correlated with leaf shape. For instance, the parallel venation found in most monocots correlates with their elongated leaf shape and wide leaf base, while reticulate venation is seen in simple entire leaves, while digitate leaves typically have venation in which three or more primary veins diverge radially from
3696-551: The leaves of vascular plants . In most cases, they lack vascular tissue, are only a single cell thick, and have no cuticle , stomata, or internal system of intercellular spaces. (The phyllids of the moss family Polytrichaceae are notable exceptions.) The phyllids of bryophytes are only present on the gametophytes , while in contrast the leaves of vascular plants are only present on the sporophytes . These can further develop into either vegetative or reproductive structures. Simple, vascularized leaves ( microphylls ), such as those of
3773-568: The less acidic, more bitter, and more highly caffeinated robusta bean ( C. canephora ) makes up most of the remaining coffee production. The natural populations of Coffea arabica are restricted to the forests of South Ethiopia and Yemen. Coffea arabica was first described scientifically by Antoine de Jussieu , who named it Jasminum arabicum after studying a specimen from the Botanic Gardens of Amsterdam . Linnaeus placed it in its own genus Coffea in 1737. Coffea arabica
3850-552: The number of stomata (pores that intake and output gases), the amount and structure of epicuticular wax and other features. Leaves are mostly green in color due to the presence of a compound called chlorophyll which is essential for photosynthesis as it absorbs light energy from the sun . A leaf with lighter-colored or white patches or edges is called a variegated leaf . Leaves can have many different shapes, sizes, textures and colors. The broad, flat leaves with complex venation of flowering plants are known as megaphylls and
3927-583: The origin of Coffea arabica is estimated between 1.08 million and 543,000 years ago and is linked to changing environmental conditions in East Africa. Wild plants grow between 9 and 12 m (30 and 39 ft) tall, and have an open branching system; the leaves are opposite, simple elliptic-ovate to oblong, 6–12 cm (2.5–4.5 in) long and 4–8 cm (1.5–3 in) broad, glossy dark green. The flowers are white, 10–15 mm in diameter, and grow in axillary clusters. The seeds are contained in
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#17327721071554004-404: The photosynthetic organelles , the chloroplasts , to light and to increase the absorption of carbon dioxide while at the same time controlling water loss. Their surfaces are waterproofed by the plant cuticle and gas exchange between the mesophyll cells and the atmosphere is controlled by minute (length and width measured in tens of μm) openings called stomata which open or close to regulate
4081-412: The plant and provides the route for transfer of water and sugars to and from the leaf. The lamina is typically the location of the majority of photosynthesis. The upper ( adaxial ) angle between a leaf and a stem is known as the axil of the leaf. It is often the location of a bud . Structures located there are called "axillary". External leaf characteristics, such as shape, margin, hairs, the petiole, and
4158-434: The presence of stipules and glands, are frequently important for identifying plants to family, genus or species levels, and botanists have developed a rich terminology for describing leaf characteristics. Leaves almost always have determinate growth. They grow to a specific pattern and shape and then stop. Other plant parts like stems or roots have non-determinate growth, and will usually continue to grow as long as they have
4235-410: The previous two. Rotation fractions are often quotients F n / F n + 2 of a Fibonacci number by the number two terms later in the sequence. This is the case for the fractions 1/2, 1/3, 2/5, 3/8, and 5/13. The ratio between successive Fibonacci numbers tends to the golden ratio φ = (1 + √5)/2 . When a circle is divided into two arcs whose lengths are in the ratio 1:φ , the angle formed by
4312-465: The primary organs responsible for transpiration and guttation (beads of fluid forming at leaf margins). Leaves can also store food and water , and are modified accordingly to meet these functions, for example in the leaves of succulent plants and in bulb scales. The concentration of photosynthetic structures in leaves requires that they be richer in protein , minerals , and sugars than, say, woody stem tissues. Accordingly, leaves are prominent in
4389-429: The primary veins run parallel and equidistant to each other for most of the length of the leaf and then converge or fuse (anastomose) towards the apex. Usually, many smaller minor veins interconnect these primary veins, but may terminate with very fine vein endings in the mesophyll. Minor veins are more typical of angiosperms, which may have as many as four higher orders. In contrast, leaves with reticulate venation have
4466-416: The products of photosynthesis (photosynthate) from the cells where it takes place, while major veins are responsible for its transport outside of the leaf. At the same time water is being transported in the opposite direction. The number of vein endings is very variable, as is whether second order veins end at the margin, or link back to other veins. There are many elaborate variations on the patterns that
4543-429: The protective spines of cacti and the insect traps in carnivorous plants such as Nepenthes and Sarracenia . Leaves are the fundamental structural units from which cones are constructed in gymnosperms (each cone scale is a modified megaphyll leaf known as a sporophyll) and from which flowers are constructed in flowering plants . The internal organization of most kinds of leaves has evolved to maximize exposure of
4620-714: The rate exchange of carbon dioxide (CO 2 ), oxygen (O 2 ) and water vapor into and out of the internal intercellular space system. Stomatal opening is controlled by the turgor pressure in a pair of guard cells that surround the stomatal aperture. In any square centimeter of a plant leaf, there may be from 1,000 to 100,000 stomata. The shape and structure of leaves vary considerably from species to species of plant, depending largely on their adaptation to climate and available light, but also to other factors such as grazing animals (such as deer), available nutrients, and ecological competition from other plants. Considerable changes in leaf type occur within species, too, for example as
4697-535: The resources to do so. The type of leaf is usually characteristic of a species (monomorphic), although some species produce more than one type of leaf (dimorphic or polymorphic ). The longest leaves are those of the Raffia palm , R. regalis which may be up to 25 m (82 ft) long and 3 m (9.8 ft) wide. The terminology associated with the description of leaf morphology is presented, in illustrated form, at Wikibooks . Where leaves are basal, and lie on
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#17327721071554774-433: The same time. They are sometimes shaken off the tree onto mats, which means ripe and unripe berries are collected together. The trees are difficult to cultivate and each tree can produce from 0.5 to 5.0 kilograms (1.1 to 11.0 lb) of dried beans, depending on the tree's individual character and the climate that season. The most valuable part of this cash crop is the beans inside. Each berry holds two locules containing
4851-446: The secondary veins, known as tertiary or third order (or higher order) veins, forming a dense reticulate pattern. The areas or islands of mesophyll lying between the higher order veins, are called areoles . Some of the smallest veins (veinlets) may have their endings in the areoles, a process known as areolation. These minor veins act as the sites of exchange between the mesophyll and the plant's vascular system. Thus, minor veins collect
4928-455: The sequence 180°, 90°, 180°, 270°. Two basic forms of leaves can be described considering the way the blade (lamina) is divided. A simple leaf has an undivided blade. However, the leaf may be dissected to form lobes, but the gaps between lobes do not reach to the main vein. A compound leaf has a fully subdivided blade, each leaflet of the blade being separated along a main or secondary vein. The leaflets may have petiolules and stipels,
5005-454: The smaller arc is the golden angle , which is 1/φ × 360° ≈ 137.5° . Because of this, many divergence angles are approximately 137.5° . In plants where a pair of opposite leaves grows from each node, the leaves form a double helix. If the nodes do not rotate (a rotation fraction of zero and a divergence angle of 0°), the two helices become a pair of parallel lines, creating a distichous arrangement as in maple or olive trees. More common in
5082-953: The species that bear them, the majority, as broad-leaved or megaphyllous plants, which also include acrogymnosperms and ferns . In the lycopods , with different evolutionary origins, the leaves are simple (with only a single vein) and are known as microphylls . Some leaves, such as bulb scales, are not above ground. In many aquatic species, the leaves are submerged in water. Succulent plants often have thick juicy leaves, but some leaves are without major photosynthetic function and may be dead at maturity, as in some cataphylls and spines . Furthermore, several kinds of leaf-like structures found in vascular plants are not totally homologous with them. Examples include flattened plant stems called phylloclades and cladodes , and flattened leaf stems called phyllodes which differ from leaves both in their structure and origin. Some structures of non-vascular plants look and function much like leaves. Examples include
5159-465: The spread of Yemen's trade. Indonesian coffees, such as Sumatran and Java, are known for their heavy body and low acidity. This makes them ideal for blending with the higher acidity coffees from Central America and East Africa . Coffea arabica accounts for 60% of the world's coffee production. C. arabica takes approximately seven years to mature fully, and it does best with 1.0–1.5 metres (39–59 in) of rain, evenly distributed throughout
5236-421: The stem is known as phyllotaxis . A large variety of phyllotactic patterns occur in nature: In the simplest mathematical models of phyllotaxis , the apex of the stem is represented as a circle. Each new node is formed at the apex, and it is rotated by a constant angle from the previous node. This angle is called the divergence angle . The number of leaves that grow from a node depends on the plant species. When
5313-547: The stomatal complex; guard cells and subsidiary cells. The epidermal cells are the most numerous, largest, and least specialized and form the majority of the epidermis. They are typically more elongated in the leaves of monocots than in those of dicots . Chloroplasts are generally absent in epidermal cells, the exception being the guard cells of the stomata . The stomatal pores perforate the epidermis and are surrounded on each side by chloroplast-containing guard cells, and two to four subsidiary cells that lack chloroplasts, forming
5390-511: The surrounding air , promoting cooling. Functionally, in addition to carrying out photosynthesis, the leaf is the principal site of transpiration , providing the energy required to draw the transpiration stream up from the roots, and guttation . Many conifers have thin needle-like or scale-like leaves that can be advantageous in cold climates with frequent snow and frost. These are interpreted as reduced from megaphyllous leaves of their Devonian ancestors. Some leaf forms are adapted to modulate
5467-480: The sustainability of arabica coffee production, leading to attempts to breed new cultivars for the changing conditions. Gourmet coffees are almost exclusively high-quality mild varieties of arabica coffee, and among the best known arabica coffee beans in the world are those from Jamaican Blue Mountain , Colombian Supremo , Tarrazú , Costa Rica , Guatemalan Antigua , and Ethiopian Sidamo . Blends consisting only of Arabica are often labelled "100% Arabica" as
5544-419: The sweet smell of jasmine flowers. Flowers opening on sunny days result in the greatest number of berries. This can be problematic and deleterious, however, as coffee plants tend to produce too many berries; this can lead to an inferior harvest and even damage yield in the following years, as the plant will favor the ripening of berries to the detriment of its own health. On well-kept plantations, overflowering
5621-632: The transportation system. Typically leaves are broad, flat and thin (dorsiventrally flattened), thereby maximising the surface area directly exposed to light and enabling the light to penetrate the tissues and reach the chloroplasts , thus promoting photosynthesis. They are arranged on the plant so as to expose their surfaces to light as efficiently as possible without shading each other, but there are many exceptions and complications. For instance, plants adapted to windy conditions may have pendent leaves, such as in many willows and eucalypts . The flat, or laminar, shape also maximizes thermal contact with
5698-484: The trees have a season and are harvested only in winter. The plants are vulnerable to damage in such poor growing conditions as cold or low pH soil , and they are also more vulnerable to pests than the C. robusta plant. It is expected that a medium-term depletion of indigenous populations of C. arabica may occur, due to projected global warming , based on IPCC modelling. Climate change—rising temperatures, longer droughts, and excessive rainfall—appears to threaten
5775-462: The vascular structure of the organ, extending into the leaf via the petiole and providing transportation of water and nutrients between leaf and stem, and play a crucial role in the maintenance of leaf water status and photosynthetic capacity. They also play a role in the mechanical support of the leaf. Within the lamina of the leaf, while some vascular plants possess only a single vein, in most this vasculature generally divides (ramifies) according to
5852-702: The year. It is usually cultivated at an altitude between 1,300 and 1,500 m (4,300 and 4,900 ft), but there are plantations that grow it as low as sea level and as high as 2,800 m (9,200 ft). The plant can tolerate low temperatures, but not frost, and it does best with an average temperature between 15 and 24 °C (59 and 75 °F). Commercial cultivars mostly only grow to about 5 m, and are frequently trimmed as low as 2 m to facilitate harvesting. Unlike Coffea canephora , C. arabica prefers to be grown in light shade. Two to four years after planting, C. arabica produces small, white, highly fragrant flowers. The sweet fragrance resembles
5929-696: Was useful in prolonging their working hours. The Arab innovation in Yemen of making a brew from roasted beans spread first among the Egyptians and Turks , and later on found its way around the world. Other scholars believe that the coffee plant was introduced from Yemen, based on a Yemeni tradition that slips of both coffee and qat were planted at Udein ('the two twigs') in Yemen in pre-Islamic times. Arabica coffee production in Indonesia began in 1699 through
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