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72-454: Lepidium peruvianum Lepidium meyenii , known as maca or Peruvian ginseng , is an edible herbaceous biennial plant of the family Brassicaceae that is native to South America in the high Andes mountains of Peru and Bolivia . It was rediscovered for commercial purposes at the Meseta de Bombón plateau close to Lake Junin in the late 1980s. It is grown for its fleshy hypocotyl that

144-467: A "hard frost" below −2 °C (28 °F). Plants likely to be damaged even by a light frost include vines—such as beans, grapes, squashes, melons—along with nightshades such as tomatoes, eggplants, and peppers. Plants that may tolerate (or even benefit from) frosts include: Even those plants that tolerate frost may be damaged once temperatures drop even lower (below −4 °C or 25 °F). Hardy perennials, such as Hosta , become dormant after

216-599: A "plant that does not produce a woody stem", and the adjective "herbaceous" as meaning "herb-like, referring to parts of the plant that are green and soft in texture". Herbaceous plants include graminoids , forbs , and ferns . Forbs are generally defined as herbaceous broad-leafed plants, while graminoids are plants with grass-like appearance including true grasses , sedges, and rushes. Herbaceous plants most often are low-growing plants, different from woody plants like trees and shrubs , tending to have soft green stems that lack lignification and their above-ground growth

288-421: A U.S.-based brewery called Andean Brewing Company became the first company to produce and commercialize beer made from maca under the brand KUKA Beer. From the black morphotype, a liquor is produced. Also, the leaves are edible or may serve as animal fodder. They can be prepared raw in salads or cooked much like L. sativum and L. campestre , which are closely related genetically. The prominent product for export

360-443: A central raceme , and are followed by 4–5 mm (0.16–0.20 in) siliculate fruits, each containing two small 2.0–2.5 mm (0.079–0.098 in) reddish-gray ovoid seeds . Seeds are the maca's only means of reproduction. Maca reproduces mainly through self-pollination and is an autogamous species. The genome consists of 64 chromosomes. Maca is a short-day plant from experiments with different day lengths. Some sources consider

432-403: A certain amount of water vapor, depending on temperature. Warmer air can hold more than colder air. When the atmosphere contains more water than it can hold at a specific temperature, its relative humidity rises above 100% becoming supersaturated , and the excess water vapor is forced to deposit onto any nearby surface, forming seed crystals . The temperature at which frost will form is called

504-672: A cultivated hectare may reach an estimated 15 tons in fresh hypocotyls, resulting in around 5 tons of dried material. According to the Ministry of Agriculture of Peru , however, average maca yields for 2005 were only 7 t/ha, with a great variation between different sites. Although maca has been cultivated outside the Andes, it is unclear whether it develops the same active constituents or potency outside of its natural habitat. Hypocotyls grown from Peruvian seeds form with difficulty at low elevations, in greenhouses, or warm climates. The average composition, on

576-664: A dry matter basis, is 60–75% carbohydrates (primarily as polysaccharides ), 10–14% protein , 8.5% dietary fiber , and 2.2% fats . Maca contains glucotropaeolin , m -methoxyglucotropaeolin, benzyl glucosinolates , polyphenols , (1 R ,3 S )-1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (MTCA), and p -methoxybenzyl isothiocyanate . Alkamides are also present in maca. Maca contains several N-benzylamides referred to as macamides that are structurally related to anandamide . No pharmacokinetic data have been published for maca. The presence of (1 R ,3 S )-1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (MTCA) in

648-438: A glass pane is exposed to very cold air on the outside and warmer, moderately moist air on the inside. If the pane is a bad insulator (for example, if it is a single-pane window), water vapour condenses on the glass, forming frost patterns. With very low temperatures outside, frost can appear on the bottom of the window even with double-pane energy-efficient windows because the air convection between two panes of glass ensures that

720-475: A heavy coating of hoar frost with big, interlocking crystals, usually needle-shaped. Rime is a type of ice deposition that occurs quickly, often under heavily humid and windy conditions. Technically speaking, it is not a type of frost, since usually supercooled water drops are involved, in contrast to the formation of hoar frost, in which water vapour desublimates slowly and directly. Ships travelling through Arctic seas may accumulate large quantities of rime on

792-542: A mass of frost crystals scatters light in all directions, the coating of frost appears white. Types of frost include crystalline frost ( hoar frost or radiation frost) from deposition of water vapor from air of low humidity, white frost in humid conditions, window frost on glass surfaces, advection frost from cold wind over cold surfaces, black frost without visible ice at low temperatures and very low humidity, and rime under supercooled wet conditions. Plants that have evolved in warmer climates suffer damage when

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864-600: A plant becomes tolerant to low temperatures. See also Cryobiology . Certain bacteria , notably Pseudomonas syringae , are particularly effective at triggering frost formation, raising the nucleation temperature to about −2 °C (28 °F). Bacteria lacking ice nucleation-active proteins ( ice-minus bacteria ) result in greatly reduced frost damage. Typical measures to prevent frost or reduce its severity include one or more of: Such measures need to be applied with discretion, because they may do more harm than good; for example, spraying crops with water can cause damage if

936-479: A process similar to the formation of dust bunnies and similar structures. Hoar frost and white frost also occur in man-made environments such as in freezers or industrial cold-storage facilities. If such cold spaces or the pipes serving them are not well insulated and are exposed to ambient humidity, the moisture will freeze instantly depending on the freezer temperature. The frost may coat pipes thickly, partly insulating them, but such inefficient insulation still

1008-430: A surface, acicular crystals (needle-like) growing outward from the surface, snowflake-shaped crystals, or even large, knifelike blades of ice covering an object, which depends on many factors such as temperature, air pressure, air motion and turbulence, surface roughness and wettability , and the level of supersaturation. For example, water vapor adsorbs to glass very well, so automobile windows will often frost before

1080-405: A woody stem, allowing plants to grow tall and transport water and nutrients over longer distances within the plant body. Since most woody plants are perennials with a longer life cycle because it takes more time and more resources (nutrients and water) to produce persistently living lignified woody stems, they are not as able to colonize open and dry ground as rapidly as herbs. The surface of herbs

1152-475: Is ephemeral and often seasonal in duration. By contrast, non-herbaceous vascular plants are woody plants that have stems above ground that remain alive, even during any dormant season, and grow shoots the next year from the above-ground parts – these include trees , shrubs , vines and woody bamboos . Banana plants are also regarded as herbaceous plants because the stem does not contain true woody tissue. Some herbaceous plants can grow rather large, such as

1224-400: Is a catalyst for dew, which in arid climates and seasons is the main type of precipitation and is necessary for the survival of vegetation, i.e. in arid areas, herbaceous plants are a generator of precipitation and the basis of an ecosystem. Most of the water vapor that turns into dew comes from the air, not the soil or clouds. The taller the herb ( surface area is the main factor though),

1296-520: Is a consequence of the nucleation process being constrained to unfold in two dimensions, unlike a snowflake, which is shaped by a similar process, but forms in three dimensions and has a fractal dimension greater than two. If the indoor air is very humid, rather than moderately so, water first condenses in small droplets, and then freezes into clear ice . Similar patterns of freezing may occur on other smooth vertical surfaces, but they seldom are as obvious or spectacular as on clear glass. White frost

1368-431: Is a solid deposition of ice that forms directly from water vapour contained in air. White frost forms when relative humidity is above 90% and the temperature below −8 °C (18 °F), and it grows against the wind direction, since air arriving from windward has a higher humidity than leeward air, but the wind must not be strong, else it damages the delicate icy structures as they begin to form. White frost resembles

1440-413: Is a source of heat loss. Advection frost (also called wind frost ) refers to tiny ice spikes that form when very cold wind is blowing over tree branches, poles, and other surfaces. It looks like rimming on the edges of flowers and leaves, and usually forms against the direction of the wind . It can occur at any hour, day or night. Window frost (also called fern frost or ice flowers ) forms when

1512-401: Is a thin layer of ice on a solid surface, which forms from water vapor that deposits onto a freezing surface. Frost forms when the air contains more water vapor than it can normally hold at a specific temperature. The process is similar to the formation of dew , except it occurs below the freezing point of water typically without crossing through a liquid state. Air always contains

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1584-426: Is both sweet and slightly bitter. The natural environment of the maca is at 11–12ºS latitude and at an elevation of 3,800–4,400 m (12,500–14,400 ft) above sea level. At this elevation, temperatures of the growing season vary from −2 to 13 °C (28 to 55 °F) in monthly mean minimum or maximum, respectively. Temperatures can decline, however, as low as −10 °C (14 °F) and frosts are common. Of

1656-406: Is called "killing frost" because white frost tends to be less cold, partly because the latent heat of freezing of the water reduces the temperature drop. Many plants can be damaged or killed by freezing temperatures or frost. This varies with the type of plant, the tissue exposed, and how low temperatures get; a "light frost" of −2 to 0 °C (28 to 32 °F) damages fewer types of plants than

1728-633: Is due partly to differences of elevation, the lower areas becoming colder on calm nights. Where static air settles above an area of ground in the absence of wind, the absorptivity and specific heat of the ground strongly influence the temperature that the trapped air attains. Hoar frost , also hoarfrost , radiation frost , or pruina , refers to white ice crystals deposited on the ground or loosely attached to exposed objects, such as wires or leaves. They form on cold, clear nights when conditions are such that heat radiates into outer space faster than it can be replaced from nearby warm objects or brought in by

1800-471: Is fused with a taproot , which is typically dried but may also be freshly cooked as a root vegetable . As a cash crop, it is primarily exported as a powder that may be raw or processed further as a gelatinized starch or as an extract . If dried, it may be processed into a flour for baking or as a dietary supplement . Its Spanish and Quechua names include maca-maca , maino , ayak chichira , and ayak willku . Antonio Vázquez de Espinosa described

1872-421: Is maca flour , a baking flour ground from the hard, dried roots. It is called harina de maca . Maca flour (powder) is a relatively inexpensive bulk commodity, like wheat flour or potato flour. The supplement industry uses both dry roots and maca flour for different types of processing and concentrated extracts. Another common form is maca, processed by gelatinization . This extrusion process separates and removes

1944-401: Is mainly grown for the consumption of its roots. The majority of harvested maca is dried. In this form, the hypocotyls can be stored for several years. In Peru, maca is prepared and consumed in various ways, although traditionally, it is always cooked. The freshly harvested hypocotyl may be roasted in a pit (called huatia ) and is considered a delicacy. Fresh roots usually are available only in

2016-411: Is not necessarily damaged when leaf temperatures drop below the freezing point of their cell contents. In the absence of a site nucleating the formation of ice crystals, the leaves remain in a supercooled liquid state, safely reaching temperatures of −4 to −12 °C (25 to 10 °F). However, once frost forms, the leaf cells may be damaged by sharp ice crystals. Hardening is the process by which

2088-465: Is not necessary. The climate is not suitable for most weeds or pests. Nearly all maca cultivation in Peru is carried out organically; maca is seldom attacked. Maca is sometimes interplanted with potatoes, as it is known to maca farmers that the plant naturally repels most root crop pests. The harvest is done manually, with the leaves left in the field as livestock feed or organic fertilizer . The yield for

2160-543: Is personified in Russian culture as Ded Moroz . Indigenous peoples of Russia such as the Mordvins have their own traditions of frost deities. English folklore tradition holds that Jack Frost , an elfish creature, is responsible for feathery patterns of frost found on windows on cold mornings. In 2024, two European Space Agency spacecraft, Exomars TGO and Mars Express , discovered a thin but very wide layer of water frost on

2232-468: Is related, but it also resembles a parsnip . The green, fragrant tops are short and lie along the ground. The thin, frilly leaves sprout in a rosette at the soil surface, not growing more than 12–20 cm (4.7–7.9 in) in height. The leaves show a dimorphism according to the reproductive stage. They are more prominent in the vegetative phase and continuously renew from the center as the outer leaves die. The off-white, self-fertile flowers are borne on

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2304-463: Is strictly linked to seasonality. Traditionally, land preparation was done by hand. Nowadays, tractor plowing is also used. As maca grows on sites where no other crops can be cultivated, it is often found after long fallows of sheep grazing pastures. Maca croplands, thus, traditionally are only fertilized with sheep and alpaca manure; however, fertilizer application could prevent soils from depleting in nutrients. Weeding or pesticide application usually

2376-422: Is the same phenomenon responsible for the formation of clouds, fog, snow, rain and other meteorological phenomena. The ice crystals of frost form as the result of fractal process development. The depth of frost crystals varies depending on the amount of time they have been accumulating, and the concentration of the water vapor ( humidity ). Frost crystals may be invisible (black), clear ( translucent ), or, if

2448-527: The contiguous United States , southern Florida around Miami Beach and the Florida Keys are the only reliably frost-free areas, as well as the Channel Islands off the coast of California . The hardiness zones in these regions are 11a and 11b. Permafrost is a layer of frozen earth underground which never heats above freezing even during summer months, remaining frozen year round. Although not frost in

2520-530: The dew point , and depends on the humidity of the air. When the temperature of the air drops below its dew point, excess water vapor is forced out of solution, resulting in a phase change directly from water vapor (a gas ) to ice (a solid). As more water molecules are added to the seeds, crystal growth occurs, forming ice crystals . Crystals may vary in size and shape, from an even layer of numerous microscopic-seeds to fewer but much larger crystals, ranging from long dendritic crystals (tree-like) growing across

2592-418: The liquid phase . The air must be humid, but not sufficiently humid to permit the condensation of liquid water, or icing will result instead of desublimation. The size of the crystals depends largely on the temperature, the amount of water vapor available, and how long they have been growing undisturbed. As a rule, except in conditions where supercooled droplets are present in the air, frost will form only if

2664-692: The 1990s to 2014. Market studies showed low acceptance of the particular maca taste by consumers when first exposed to it, creating a barrier for popularity of this food as a culinary vegetable. The economic interest existed more in the perceived but unproven health effects of the root's constituents supplied as an extract in a dietary supplement. By 2014, agricultural and market interest in maca grew in China, but with challenges from Peruvian institutions who accused Chinese companies of illegally exporting maca and of biopiracy , as several Chinese patents had been filed to improve maca's propagation and genetic diversity. Maca

2736-533: The Earth to reach deep enough to thaw the permafrost layer. The permafrost may begin from the surface of the ground or many meters beneath it, and may extend from just a meter to over a thousand meters in thickness. Permafrost contains a significant portion of the Earth's water and carbon, and prevents surface water from penetrating very deep into the ground, making it responsible in part for the typical taiga and spruce bog environments common in northern latitudes. Frost

2808-462: The air experiences a drop in temperature bringing it below its dew point, for example, when the temperature falls after the Sun sets. In temperate climates , it most commonly appears on surfaces near the ground as fragile white crystals ; in cold climates, it occurs in a greater variety of forms. The propagation of crystal formation occurs by the process of nucleation , in specific, water nucleation , which

2880-462: The air temperature a few feet above ground is well above freezing. The word "hoar" comes from an Old English adjective that means "showing signs of old age". In this context, it refers to the frost that makes trees and bushes look like white hair. Hoar frost may have different names depending on where it forms: When surface hoar covers sloping snowbanks, the layer of frost crystals may create an avalanche risk; when heavy layers of new snow cover

2952-404: The analysis of annual growth rings in the secondary root xylem . Herbaceous plants do not produce perennializing above-ground structures using lignin , which is a complex phenolic polymer deposited in the secondary cell wall of all vascular plants. The development of lignin during vascular plant evolution provided mechanical strength, rigidity, and hydrophobicity to secondary cell walls creating

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3024-461: The atmospheric sense, it consists of dirt, soil, sand, rocks, clay, or organic matter (peat) bound firmly together by ice crystals, making the material very hard and difficult to penetrate. Permafrost exists in the colder climates of the Arctic and Antarctic, such as Russia, Canada, Alaska, Norway, Greenland, or Antarctica, where the warmer conditions of summer are insufficient to penetrate the insulation of

3096-399: The bottom part of the glazing unit is colder than the top part. On unheated motor vehicles, the frost usually forms on the outside surface of the glass first. The glass surface influences the shape of crystals, so imperfections, scratches, or dust can modify the way ice nucleates . The patterns in window frost form a fractal with a fractal dimension greater than one, but less than two. This

3168-481: The color differences. Maca hypocotyls may be gold or cream, red, purple, blue, black, or green. Each is considered a "genetically unique variety," as the seeds of the parent plants grow to have roots of the same color. Specific phenotypes (in maca, 'phenotype' pertains mainly to root color) have been propagated exclusively to increase commercial interest. Cream-colored roots are the most widely grown and are favored in Peru for their enhanced sweetness and size. Black maca

3240-521: The condition "when persisting over more than one growing season, the parts of the shoot dying back seasonally". Some orchids, such as species of Phalaenopsis , are described in some sources (including the authoritative Plants of the World Online ) as "herbs" but with "leaves persistent or sometimes deciduous". In the glossary of Flora of the Sydney Region , Roger Charles Carolin defines "herb" as

3312-670: The cultivated maca L. meyenii . The Latin name recognized by the USDA similarly continues to be Lepidium meyenii . It has been debated whether it is botanically correct to consider meyenii and peruvianum to be distinct from one another. A 2015 multi-center study found differences in taxonomy, visual appearance, phytochemical profiles and DNA sequences when comparing L. meyenii and L. peruvianum , suggesting that they are different and that their names should not be considered synonyms. The growth habit, size, and proportions of maca are roughly similar to those of radishes and turnips , to which it

3384-561: The cultivated plants, maca is one of the most frost tolerant. Strong winds and sunlight are also characteristics of the native habitat of the maca. Maca today is still mainly cultivated in Peru , in the high Andes of Bolivia, and to a small extent also in Brazil . Maca can be cultivated beyond its natural elevation range, over 4,400 m (14,400 ft) above sea level. Maca (Peruvian ginseng) seedlings usually emerge about one month after sowing, with

3456-452: The deposition surface is colder than the surrounding air. For instance, frost may be observed around cracks in cold wooden sidewalks when humid air escapes from the warmer ground beneath. Other objects on which frost commonly forms are those with low specific heat or high thermal emissivity , such as blackened metals, hence the accumulation of frost on the heads of rusty nails. The apparently erratic occurrence of frost in adjacent localities

3528-678: The end of the growing season, but parts of the plant survive under or close to the ground from season to season (for biennials, until the next growing season, when they grow and flower again, then die). New growth can also develop from living tissues remaining on or under the ground, including roots , a caudex (a thickened portion of the stem at ground level) or various types of underground stems , such as bulbs , corms , stolons , rhizomes and tubers . Examples of herbaceous biennials include carrot , parsnip and common ragwort ; herbaceous perennials include potato , peony , hosta , mint , most ferns and most grasses . Frost Frost

3600-533: The evidence for the effectiveness of maca as a treatment for menopausal symptoms in women inconclusive. Herbaceous The fourth edition of the Shorter Oxford English Dictionary defines "herb" as: The same dictionary defines "herbaceous" as: Botanical sources differ from each other on the definition of "herb". For instance, the Hunt Institute for Botanical Documentation includes

3672-696: The extracts of maca indicate a potential safety issue as a monoamine oxidase inhibitor (re. which see β-carboline ) and possibility as a mutagen . Due to these potential mutagenic properties of MTCA, the Agency for Sanitary Security in France warned consumers about the possible health risks of powdered maca root, a declaration disputed on the assumption that MTCA would be deactivated by boiling to process maca roots. MTCA-like compounds are associated with craving behaviour. Due to its purported effect on fertility , maca grew in agricultural, commercial, and research interest from

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3744-407: The first frosts and regrow when spring arrives. The entire visible plant may turn completely brown until the spring warmth, or may drop all of its leaves and flowers, leaving the stem and stalk only. Evergreen plants, such as pine trees, withstand frost although all or most growth stops. Frost crack is a bark defect caused by a combination of low temperatures and heat from the winter sun. Vegetation

3816-414: The frosty surface, furry crystals standing out from the old snow hold off the falling flakes, forming a layer of voids that prevents the new snow layers from bonding strongly to the old snow beneath. Ideal conditions for hoarfrost to form on snow are cold, clear nights, with very light, cold air currents conveying humidity at the right rate for growth of frost crystals. Wind that is too strong or warm destroys

3888-405: The furry crystals, and thereby may permit a stronger bond between the old and new snow layers. However, if the winds are strong enough and cold enough to lay the crystals flat and dry, carpeting the snow with cold, loose crystals without removing or destroying them or letting them warm up and become sticky, then the frost interface between the snow layers may still present an avalanche danger, because

3960-609: The genus Musa , to which the banana belongs. Some relatively fast-growing herbaceous plants (especially annuals) are pioneers , or early-successional species. Others form the main vegetation of many stable habitats, occurring for example in the ground layer of forests , or in naturally open habitats such as meadow , salt marsh or desert . Some habitats, like grasslands and prairies and savannas , are dominated by herbaceous plants along with aquatic environments like ponds , streams and lakes . The age of some herbaceous perennial plants can be determined by herbchronology ,

4032-523: The lowland tropics, where they cover almost all land except at altitudes above about 3,000 metres or 9,800 feet near the equator and around 2,000 metres or 6,600 feet in the semiarid areas in tropical regions. Some areas on the oceanic margins of the subtropics are also frost-free, as are highly oceanic areas near windward coasts. The most poleward frost-free areas are the lower altitudes of the Azores , Île Amsterdam , Île Saint-Paul , and Tristan da Cunha . In

4104-451: The maca an annual plant, as in favorable years, it can complete a lifecycle within a year. Maca is the only member of the genus Lepidium with a fleshy hypocotyl , which is fused with the taproot to form a rough inverted pear-shaped body. Traditionally, native growers have acknowledged four varieties of maca based on their root color: cream-yellow, half-purple, purple, and black; varying levels of anthocyanin are primarily responsible for

4176-517: The more dew it produces, so a short cut of the herbs necessitates watering. For example, if you frequently and shortly cut the grass without watering in an arid zone, then desertification occurs. Most herbaceous plants have a perennial (85%) life cycle but some are annual (15%) or biennial (<1%). Annual plants die completely at the end of the growing season or when they have flowered and fruited, and then new plants grow from seed. Herbaceous perennial and biennial plants may have stems that die at

4248-461: The onset of the rainy season in October. In the vegetative phase, from May to June, the lower part of the hypocotyl, as well as the upper part of the tap root, grows in size. After 260 to 280 days, it is formed into the harvestable hypocotyl. If the root is left in the soil, it is dormant for two to three months in the time of the cold, dry season until August. Then, it will form a generative shoot on which

4320-399: The paint, and large hoar-frost crystals can grow very rapidly when the air is very cold, calm, and heavily saturated, such as during an ice fog . Frost may occur when warm, moist air comes into contact with a cold surface, cooling it below its dew point, such as warm breath on a freezing window. In the atmosphere, it more often occurs when both the air and the surface are below freezing, when

4392-437: The plant following his visit to Peru circa 1598, and Bernabé Cobo described this plant in the early 17th century. Gerhard Walpers named the species Lepidium meyenii in 1843. In the 1990s, Gloria Chacon further distinguished a different species. She considered the widely cultivated natural maca of today to be a newer domesticated species, L. peruvianum . However, most botanists doubt this distinction and continue to call

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4464-466: The plants become overburdened with ice. An effective, low cost method for small crop farms and plant nurseries, exploits the latent heat of freezing . A pulsed irrigation timer delivers water through existing overhead sprinklers at a low volumes to combat frosts down to −5 °C (23 °F). If the water freezes, it gives off its latent heat, preventing the temperature of the foliage from falling much below zero. Frost-free areas are found mainly in

4536-411: The rigging. Unlike hoar frost, which has a feathery appearance, rime generally has an icy, solid appearance. Black frost (or "killing frost") is not strictly speaking frost at all, because it is the condition seen in crops when the humidity is too low for frost to form, but the temperature falls so low that plant tissues freeze and die, becoming blackened, hence the term "black frost". Black frost often

4608-441: The seeds ripen five months later. One plant can form up to 1000 tiny seeds, 1600 of which weigh about one gram. Thus, only relatively few plants are needed for propagation. The cultivated plants are selected for preferred size and color, then placed 50–100 mm deep in pits with alternate layers of grass and soil to protect them from drying out. They are fertilized heavily, as maca is an exhaustive crop of soil. The cultivation cycle

4680-432: The solid surface on which they grow. The main difference between the ice coatings and frost spicules arises because the crystalline spicules grow directly from desublimation of water vapour from air, and desublimation is not a factor in icing of freezing surfaces. For desublimation to proceed, the surface must be below the frost point of the air, meaning that it is sufficiently cold for ice to form without passing through

4752-407: The surface itself is colder than freezing, ice will form on it. If the water deposits as a liquid that then freezes, it forms a coating that may look glassy, opaque, or crystalline, depending on its type. Depending on context, that process may also be called atmospheric icing . The ice it produces differs in some ways from crystalline frost, which consists of spicules of ice that typically project from

4824-421: The temperature falls low enough to freeze the water in the cells that make up the plant tissue . The tissue damage resulting from this process is known as "frost damage". Farmers in those regions where frost damage has been known to affect their crops often invest in substantial means to protect their crops from such damage. If a solid surface is chilled below the dew point of the surrounding humid air, and

4896-489: The texture of the frost crystals differs from the snow texture, and the dry crystals will not stick to fresh snow. Such conditions still prevent a strong bond between the snow layers. In very low temperatures where fluffy surface hoar crystals form without subsequently being covered with snow, strong winds may break them off, forming a dust of ice particles and blowing them over the surface. The ice dust then may form yukimarimo , as has been observed in parts of Antarctica, in

4968-525: The tough fiber from the roots using gentle heat and pressure, as raw maca is difficult to digest due to its thick fibers. Archaeological evidence exists for varying degrees of cultivation of maca in the Lake Junin region from around 1700 BC to 1200 AD. Maca has been harvested and used by humans in the puna grasslands of the Andean Mountains for centuries. Contrary to frequent claims that maca cultivation

5040-405: The vicinity of the growers. The root can also be mashed and boiled to produce a sweet, thick liquid, then dried and mixed with milk to form a porridge, mazamorra . The cooked roots are also used with other vegetables in empanadas , jams, or soups. The root may be ground to produce flour for bread, cakes, or pancakes. If fermented, a weak beer called chicha de maca may be produced. In 2010,

5112-428: The wind. Under suitable circumstances, objects cool to below the frost point of the surrounding air, well below the freezing point of water. Such freezing may be promoted by effects such as flood frost or frost pocket . These occur when ground-level radiation cools air until it flows downhill and accumulates in pockets of very cold air in valleys and hollows. Hoar frost may freeze in such low-lying cold air even when

5184-588: Was common in what is today Peru, until the late 1980s, maca has been cultivated only in a limited area around Lake Junin in central Peru. Historically, maca was often traded for lowland tropical food staples, such as maize , rice , manioc (tapioca roots), quinoa , and papaya . It also was used as a form of payment for Spanish imperial taxes. Maca is said to have medicinal properties, but scientific research remains inconclusive. A 2016 systematic review found evidence suggesting that it improves semen quality in healthy and infertile men. A 2011 systematic review found

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