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46-481: Due to its geographic location, the valley has a considerably milder climate than that in other parts of Bulgaria. The slopes that surround the valley are covered with venerable coniferous forests, mainly of spruce . The second highest peak of the Rhodopes, Golyama Syutkya, is located nearby, and an important city in the valley is Velingrad . The valley takes its name from the medieval Bulgarian fortress of Tsepina ,

92-441: A petri dish or test tube). During germination, the tube cell elongates into a pollen tube . In the flower, the pollen tube then grows towards the ovule where it discharges the sperm produced in the pollen grain for fertilization. The germinated pollen grain with its two sperm cells is the mature male microgametophyte of these plants. Since most plants carry both male and female reproductive organs in their flowers, there

138-413: A spore , such as the spores of fungi , ferns, bacteria , and the growth of the pollen tube from the pollen grain of a seed plant . Germination is usually the growth of a plant contained within a seed resulting in the formation of the seedling. It is also the process of reactivation of metabolic machinery of the seed resulting in the emergence of radicle and plumule . The seed of a vascular plant

184-471: A 3-year-old seedling may be considered established; in moist habitats, seedlings may need 4 or 5 years to become established on mineral soil, possibly longer on litter seedbeds. Growth remains very slow for several to many years. Three years after shelterwood felling in subalpine Alberta, dominant regeneration averaged 5.5 cm in height in scarified blocks, and 7.3 cm in non-scarified blocks (Day 1970), possibly reflecting diminished fertility with

230-460: A degree, these classification procedures have important limitations; genetic composition of the seeds produced by a stand is determined by both the seed trees and the pollen parents, and species classification of hybrid seedlots and estimates of their level of introgression on the basis of seed-tree characteristics can be unreliable when hybrid seedlots vary in their introgressiveness in consequence of spatial and temporal variations in contributions from

276-473: A major hormone in the germination process. Another factor that promotes germination is HFR1 which accumulates in light in some way and forms inactive heterodimers with PIF1. Although the exact mechanism is not known, nitric oxide (NO) plays a role in this pathway as well. NO is thought to repress PIF1 gene expression and stabilises HFR1 in some way to support the start of germination. Bethke et al. (2006) exposed dormant Arabidopsis seeds to NO gas and within

322-494: A major role in integrating progression through germination with repair responses to the DNA damages accumulated by the aged seed. The part of the plant that first emerges from the seed is the embryonic root, termed the radicle or primary root. It allows the seedling to become anchored in the ground and start absorbing water. After the root absorbs water, an embryonic shoot emerges from the seed. This shoot comprises three main parts:

368-429: A plant hormone largely responsible for seed dormancy. The balance between GA and ABA is important. When ABA levels are higher than GA then that leads to dormant seeds and when GA levels are higher, seeds germinate. The switch between seed dormancy and germination needs to occur at a time when the seed has the best chances of surviving and an important cue that begins the process of seed germination and overall plant growth

414-459: A protective coat containing several cells (up to 8 in gymnosperms, 2–3 in flowering plants). One of these cells is a tube cell . Once the pollen grain lands on the stigma of a receptive flower (or a female cone in gymnosperms), it takes up water and germinates. Pollen germination is facilitated by hydration on the stigma, as well as by the structure and physiology of the stigma and style. Pollen can also be induced to germinate in vitro (in

460-510: A reduction in the mean germination time, an increase in the coefficient of germination velocity, the germination index and germination percentage after administration of exogenous glutamine to plants. Seed quality deteriorates with age, and this is associated with accumulation of genome damage. During germination, repair processes are activated to deal with accumulated DNA damage . In particular, single- and double-strand breaks in DNA can be repaired. The DNA damage checkpoint kinase ATM has

506-430: A spore-shedding adult plant. Bacterial spores can be exospores or endospores which are dormant structures produced by a number of different bacteria. They have no or very low metabolic activity and are formed in response to adverse environmental conditions. They allow survival and are not a form of reproduction. Under suitable conditions the spore germinates to produce a viable bacterium. Endospores are formed inside

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552-503: A tree is a spruce is not difficult; evergreen needles that are more or less quadrangled, and especially the pulvinus , give it away. Beyond that, determination can become more difficult. Intensive sampling in the Smithers/Hazelton/Houston area of British Columbia showed Douglas (1975), according to Coates et al. (1994), that cone scale morphology was the feature most useful in differentiating species of spruce;

598-671: Is a stub . You can help Misplaced Pages by expanding it . Spruce About 35; see text. A spruce is a tree of the genus Picea ( / p aɪ ˈ s iː . ə / py- SEE -ə ), a genus of about 40 species of coniferous evergreen trees in the family Pinaceae , found in the northern temperate and boreal ( taiga ) regions of the Earth. Picea is the sole genus in the subfamily Piceoideae . Spruces are large trees, from about 20 to 60 m (about 60–200 ft) tall when mature, and have whorled branches and conical form. Spruces can be distinguished from other genera of

644-432: Is a high risk of self-pollination and thus inbreeding . Some plants use the control of pollen germination as a way to prevent this self-pollination. Germination and growth of the pollen tube involve molecular signaling between stigma and pollen. In self-incompatibility in plants , the stigma of certain plants can molecularly recognize pollen from the same plant and prevent it from germinating. Germination can also refer to

690-426: Is a small package produced in a fruit or cone after the union of male and female reproductive cells . All fully developed seeds contain an embryo and, in most plant species some store of food reserves, wrapped in a seed coat. Dormant seeds are viable seeds that do not germinate because they require specific internal or environmental stimuli to resume growth. Under proper conditions, the seed begins to germinate and

736-558: Is a subjective concept based on the idea that once a seedling has successfully reached a certain size, not much is likely to prevent its further development. Criteria vary, of course, but Noble and Ronco (1978), for instance, considered that seedlings four to five years old, or 8 cm to 10 cm tall, warranted the designation "established", since only unusual factors such as snow mold , fire , trampling , or predation would then impair regeneration success. Eis (1967) suggested that in dry habitats on either mineral soil or litter seedbeds

782-401: Is the photoreceptor that is responsible for the beginning stages of germination. When red light is present, PHYB is converted to its active form and moves from the cytoplasm to the nucleus where it upregulates the degradation of PIF1 . PIF1, phytochrome-interaction-factor-1, negatively regulates germination by increasing the expression of proteins that repress the synthesis of gibberellin (GA),

828-431: The cotyledons (seed leaves), the section of shoot below the cotyledons ( hypocotyl ), and the section of shoot above the cotyledons ( epicotyl ). The way the shoot emerges differs among plant groups. Epigeal germination (or epigeous germination) is a botanical term indicating that the germination takes place above the ground. In epigeal germination, the hypocotyl elongates and forms a hook, pulling rather than pushing

874-418: The cotyledons and apical meristem through the soil. Once it reaches the surface, it straightens and pulls the cotyledons and shoot tip of the growing seedlings into the air. Beans , tamarind, and papaya are examples of plants that germinate this way. Germination can also be done by hypogeal germination (or hypogeous germination), where the epicotyl elongates and forms the hook. In this type of germination,

920-434: The larvae of some Lepidoptera (moth and butterfly) species, such as the eastern spruce budworm . They are also used by the larvae of gall adelgids ( Adelges species). In the mountains of western Sweden , scientists have found a Norway spruce , nicknamed Old Tjikko , which by reproducing through layering , has reached an age of 9,550 years and is claimed to be the world's oldest known living tree. Determining that

966-466: The World Online accepted 37 species. The grouping is based on Ran et al. (2006). There are also a number of extinct species identified from fossil evidence: Germination Germination is the process by which an organism grows from a seed or spore . The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm , the growth of a sporeling from

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1012-687: The capital of the domain of Despot Alexius Slav in the 13th century, which was excavated near the village of Dorkovo . In the early 17th century, the Eastern Orthodox Bulgarian inhabitants of the valley were Islamized by the Ottoman authorities of the time, and thus today the population is mixed, with both Orthodox Bulgarians and Pomaks (Muslim Bulgarians) inhabiting the valley. 42°1′N 24°5′E  /  42.017°N 24.083°E  / 42.017; 24.083 This Pazardzhik Province , Bulgaria location article

1058-442: The cotyledons stay underground where they eventually decompose. Peas, chickpeas and mango, for example, germinate this way. In monocot seeds, the embryo's radicle and cotyledon are covered by a coleorhiza and coleoptile , respectively. The coleorhiza is the first part to grow out of the seed, followed by the radicle. The coleoptile is then pushed up through the ground until it reaches the surface. There, it stops elongating and

1104-643: The embryo resumes growth, developing into a seedling. Disturbance of soil can result in vigorous plant growth by exposing seeds already in the soil to changes in environmental factors where germination may have previously been inhibited by depth of the seeds or soil that was too compact. This is often observed at gravesites after a burial. Seed germination depends on both internal and external conditions. The most important external factors include right temperature , water , oxygen or air and sometimes light or darkness . Various plants require different variables for successful seed germination. Often this depends on

1150-466: The emergence of cells from resting spores and the growth of sporeling hyphae or thalli from spores in fungi , algae and some plants. Conidia are asexual reproductive (reproduction without the fusing of gametes) spores of fungi which germinate under specific conditions. A variety of cells can be formed from the germinating conidia. The most common are germ tubes which grow and develop into hyphae. The initial formation and subsequent elongation of

1196-491: The establishment can be so high that many species have adapted to produce large numbers of seeds. In agriculture and gardening , the germination rate describes how many seeds of a particular plant species , variety or seedlot are likely to germinate over a given period. It is a measure of germination time course and is usually expressed as a percentage, e.g., an 85% germination rate indicates that about 85 out of 100 seeds will probably germinate under proper conditions over

1242-464: The family Pinaceae by their needles (leaves), which are four-sided and attached singly to small persistent peg-like structures ( pulvini or sterigmata ) on the branches, and by their cones (without any protruding bracts ), which hang downwards after they are pollinated. The needles are shed when 4–10 years old, leaving the branches rough with the retained pegs. In other similar genera, the branches are fairly smooth. Spruce are used as food plants by

1288-509: The first leaves emerge. When a seed germinates without undergoing all four stages of seed development, i.e., globular, heart shape, torpedo shape, and cotyledonary stage, it is known as precocious germination. Another germination event during the life cycle of gymnosperms and flowering plants is the germination of a pollen grain after pollination . Like seeds, pollen grains are severely dehydrated before being released to facilitate their dispersal from one plant to another. They consist of

1334-563: The following spring. More than half of spruce seedling mortality probably occurs during the first growing season and is also very high during the first winter, when seedlings are subjected to freezing damage, frost heaving and erosion, as well as smothering by litter and snow-pressed vegetation. Seedlings that germinate late in the growing season are particularly vulnerable because they are tiny and have not had time to harden off fully. Mortality rates generally decrease sharply thereafter, but losses often remain high for some years. "Establishment"

1380-1606: The fossil record is from the Early Cretaceous ( Valanginian ) of western Canada, around 136 million years old. P. sitchensis (Bongard) Carrière P. breweriana Watson P. likiangensis (Franchet) Pritzel P. farreri Page & Rushforth P. spinulosa (Griffith) Henry P. schrenkiana Fischer & Meyer P. smithiana (Wallich) Boiss. P. glauca (Moench) Voss P. engelmannii Parry ex Engelmann P. martinezii T.F.Patt. P. chihuahuana Martínez P. alcoquiana (Veitch ex Lindley) Carrière P. brachytyla (Franchet) Pritzel P. neoveitchii Masters P. morrisonicola Hayata P. purpurea Masters P. wilsonii Masters P. orientalis (von Linné) Peterm. P. maximowiczii Regel ex Masters P. polita (Siebold & Zuccarini) Carrière P. pungens Engelmann P. glehnii (Schmidt) Masters P. jezoensis (Sieb. & Zuccarini) Carrière P. rubens Sargent P. mariana (Miller) Britton, Sterns & Poggenburg P. omorika (Pančić) Purkyne P. obovata Ledeb. P. abies (von Linné) Karsten P. koyamae Shiras. P. asperata Masters P. koraiensis Nakai P. torano (Siebold ex Koch) Koehne P. retroflexa Masters P. shirasawae Hayashi P. crassifolia Komarov P. meyeri Rehder & Wilson As of April 2022 , Plants of

1426-404: The free-living amoebas of slime molds). In plants such as bryophytes , ferns , and a few others, spores germinate into independent gametophytes . In the bryophytes (e.g., mosses and liverworts ), spores germinate into protonemata , similar to fungal hyphae, from which the gametophyte grows. In ferns , the gametophytes are small, heart-shaped prothalli that can often be found underneath

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1472-472: The germ tube in the fungus Aspergillus niger has been captured in 3D using holotomography microscopy. Another type of cell is a conidial anastomosis tube (CAT); these differ from germ tubes in that they are thinner, shorter, lack branches, exhibit determinate growth and home toward each other. Each cell is of a tubular shape, but the conidial anastomosis tube forms a bridge that allows fusion between conidia. In resting spores , germination involves cracking

1518-441: The germination period given. Seed germination rate is determined by the seed genetic composition, morphological features and environmental factors. The germination rate is useful for calculating the number of seeds needed for a given area or desired number of plants. For seed physiologists and seed scientists "germination rate" is the reciprocal of time taken for the process of germination to complete starting from time of sowing . On

1564-848: The individual seed variety and is closely linked to the ecological conditions of a plant's natural habitat . For some seeds, their future germination response is affected by environmental conditions during seed formation; most often these responses are types of seed dormancy . Most common annual vegetables have optimal germination temperatures between 75–90 F (24–32 C), though many species (e.g. radishes or spinach ) can germinate at significantly lower temperatures, as low as 40 F (4 C), thus allowing them to be grown from seeds in cooler climates. Suboptimal temperatures lead to lower success rates and longer germination periods. Some live seeds are dormant and need more time, and/or need to be subjected to specific environmental conditions before they will germinate. Seed dormancy can originate in different parts of

1610-418: The length, width, length: width ratio, the length of free scale (the distance from the imprint of the seed wing to the tip of the scale), and the percentage free scale (length of free scale as a percentage of the total length of the scale) were most useful in this regard. Daubenmire (1974), after range-wide sampling, had already recognized the importance of the two latter characters. Taylor (1959) had noted that

1656-424: The midsection of each of ten cones from each of five trees in the population of interest. Without cones, morphological differentiation among spruce species and their hybrids is more difficult. Species classification for seeds collected from spruce stands in which introgressive hybridization between white and Sitka spruces ( P. sitchensis ) may have occurred is important for determining appropriate cultural regimens in

1702-436: The most obvious morphological difference between typical Picea glauca and typical P. engelmannii was the cone scale, and Horton (1956,1959) found that the most useful diagnostic features of the two spruces are in the cone; differences occur in the flower, shoot and needle, "but those in the cone are most easily assessed" (Horton 1959). Coupé et al. (1982) recommended that cone scale characters be based on samples taken from

1748-540: The mother cell, whereas exospores are formed at the end of the mother cell as a bud. As mentioned earlier, light can be an environmental factor that stimulates the germination process. The seed needs to be able to determine when is the perfect time to germinate and they do that by sensing environmental cues. Once germination starts, the stored nutrients that have accumulated during maturation start to be digested which then supports cell expansion and overall growth. Within light-stimulated germination, phytochrome B ( PHYB )

1794-450: The next 4 days, 90% of the seeds broke dormancy and germinated. The authors also looked at how NO and GA effects the vacuolation process of aleurone cells that allow the movement of nutrients to be digested. A NO mutant resulted in inhibition of vacuolation but when GA was later added the process was active again leading to the belief that NO is prior to GA in the pathway. NO may also lead to the decrease in sensitivity of abscisic acid (ABA),

1840-818: The nursery. If, for instance, white spruce grown at container nurseries in southwestern British Columbia are not given an extended photoperiod, leader growth ceases early in the first growing season, and seedlings do not reach the minimum height specifications. But, if an extended photoperiod is provided for Sitka spruce, seedlings become unacceptably tall by the end of the first growing season. Species classification of seedlots collected in areas where hybridization of white and Sitka spruces has been reported has depended on (i) easily measured cone scale characters of seed trees, especially free scale length, (ii) visual judgements of morphological characters, e.g., growth rhythm, shoot and root weight, and needle serration, or (iii) some combination of (i) and (ii) (Yeh and Arnott 1986). Useful to

1886-610: The other hand, the number of seed able to complete germination in a population (i.e. seed lot) is referred to as germination capacity . Soil salinity is one of the stress factors that can limit the germination rate. Environmental stress activates some stress-related activities [CuZn- superoxide dismutase (SOD), Mn-SOD, L-ascorbate oxidase (AO), DNA polymerase Delta 1 (POLD)-1, Chaperon (CHAPE) and heat shock protein (HSP)-21], genetic template stability and photosynthetic pigment activation. Application of exogenic glutamine limiting this process. Research carried out on onion seeds shows

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1932-727: The pollen parent (Yeh and Arnott 1986). Secondly, morphological characters are markedly influenced by ontogenetic and environmental influences, so that to discern spruce hybrid seedlot composition with accuracy, hybrid seedlots must differ substantially in morphology from both parent species. Yeh and Arnott (1986) pointed out the difficulties of estimating accurately the degree of introgression between white and Sitka spruces; introgression may have occurred at low levels, and/or hybrid seed lots may vary in their degree of introgression in consequence of repeated backcrossing with parental species. Spruce seedlings are most susceptible immediately following germination , and remain highly susceptible through to

1978-527: The production of barley malt . In some definitions, the appearance of the radicle marks the end of germination and the beginning of "establishment", a period that utilizes the food reserves stored in the seed. Germination and establishment as an independent organism are critical phases in the life of a plant when they are the most vulnerable to injury, disease, and water stress. The germination index can be used as an indicator of phytotoxicity in soils. The mortality between dispersal of seeds and completion of

2024-484: The removal of the A horizon. DNA analyses have shown that traditional classifications based on the morphology of needle and cone are artificial. A 2006 study found that P. breweriana had a basal position, followed by P. sitchensis , and the other species were further divided into three clades , suggesting that Picea originated in North America. The oldest record of spruce that has been found in

2070-502: The seed, for example, within the embryo; in other cases the seed coat is involved. Dormancy breaking often involves changes in membranes, initiated by dormancy-breaking signals. This generally occurs only within hydrated seeds. Factors affecting seed dormancy include the presence of certain plant hormones, notably abscisic acid , which inhibits germination, and gibberellin , which ends seed dormancy. In brewing , barley seeds are treated with gibberellin to ensure uniform seed germination for

2116-439: The thick cell wall of the dormant spore. For example, in zygomycetes the thick-walled zygosporangium cracks open and the zygospore inside gives rise to the emerging sporangiophore. In slime molds , germination refers to the emergence of amoeboid cells from the hardened spore. After cracking the spore coat, further development involves cell division, but not necessarily the development of a multicellular organism (for example in

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