Educando científicos: 6 webs de ciencia para niños y jóvenes
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Si no, los frutos ofertas de forex en londres para espanoles 2016 vendidos en mercados locales. El ancestro silvestre es desconocido. No hibrida con ninguna otra especie cultivada ni variedad silvestre. Ha sido descrita en TC. Tallos vigorosos, ligeramente angulosos. Pero otras especies de Cucurbita pueden presentar hojas como de higuera: Algunos autores han propuesto que el origen de C.
Se cultiva en varios tipos de suelo, aunque prefiere aquellos que son capaces de retener humedad y con buen drenaje, aunque no soporta suelos totalmente arcillosos. Para esta especie el rango de altitud es ofertas de forex en londres para espanoles 2016 m. Es la especie menos diversa de todas las especies cultivadas de Cucurbita y no se sabe que existan cultivares comerciales de ella. Las flores ofertas de forex en londres para espanoles 2016 brotes tiernos de C.
El nombre puede haberse propagado con el de una ofertas de forex en londres para espanoles 2016 exitosa. De Wikipedia, la enciclopedia libre. Successful hybrids have been produced in a very low percentage of the pollinations between C. Only partially developed embryos form, and embryo culture must be employed to obtain subsequent generations.
Unfortunately, sterility barriers have thus far prevented obtaining progeny beyond the F1 and first backcross generations. Variable results, however, have been obtained when different cultivars of a species are used. It is hoped that more compatible cultivar combinations may exist.
Evidence for these two forms was not documented nor have they been observed by the author. Taxonomic keys to the squashes invariably delineate C. To further confuse matters, it is sometimes stated that C.
All domesticated species of Cucurbita have extensive fibrous root systems and indeterminate growth. Under suitable growing conditions, each of these species, with the exception of bush varieties, will continue to grow indefinitely when the stems are ofertas de forex en londres para espanoles 2016 to root at the nodes.
Cucurbita ficifoliahowever, is grown in the high-altitude tropics, where it will often maintain vigor through the cool winters while the other, less cold-tolerant species perish, thereby appearing to differ from the other cultivated cucurbits grown in the same region.
In warmer climates, landraces of C. All of the domesticated squash species are usually grown as annuals, but in their native habitats, i. The buff-seeded form, occurs througout the range, usually in the same field with black-seeded plants. The fruits have basically three different color patterns that occur throughout Mexico, Central America, and South America Figure 2: Slight variations of the reticulations and stripes occur, but nothing like the wide assortment of color variants, warts, corky outgrowths, and shapes and sizes that occur in the fruits of the other domesticated species.
There is no association between seed color and fruit color. Uses of these various forms of C. While this is generally true, not all accessions of C. There are accessions of C. On the other hand, there are accesions of squash, primarily in the species C.
This facilitates recognition of the species but has given a misleading impression of its uniqueness. The fruits, which are the part of the plant most likely to have undergone diversification as a result of human selection, are relatively uniform in shape, rind and flesh characteristics.
This is in marked contrast to the other species of squash, in which numerous cultivars of striking variation exist. The stem trichomes of C. The peduncle is hard, smoothly angled, and slightly flaring at the attachment to the fruit, like that of C. The exterior color and shape of the fruit are very similar to some landraces of C. The fruits of C. In summary, of the three characters most often used in taxonomic keys to identify C.
Other species, such as C. Furthermore, most species of Cucurbita and many other related genera are heterophyllous, with late-developing leaves generally more deeply lobed than those produced early in the growth cycle. Unfortunately, most herbarium specimens of cucurbits include only one stage of leaf development.
The voucher specimens indicate that they are C. It is the only species of Cucurbita with black seeds, but not all C. There are landraces of C. As already mentioned, C. The shape of the seeds is fairly diagnostic, however. They are large, mm in lenght, and oblong-ellipsoidal with a width-to-lenght ratio of 3: They are flat in cross section and hard, without a thick, spongy epidermis that is characteristic of the seeds of C. Furthermore, the surface of the seed appears minutely pitted or pebbled and not polished or crazed like the surface of the seeds of C.
There is a uniformly thin margin around the edge of C. Ofertas de forex en londres para espanoles 2016 other species of Cucurbita have glabrous filaments or filaments with just a few scattered trichomes at their base. The only exceptions to this are C. Trichomes on the axis of C. Like all other species of CucurbitaC. However, it is primarily used under sustainable agriculture systems in Latin America, where personal observations and herbarium records show that it is generally grown between and m above sea level.
The Latin American distribution of C. The climate in these areas is generally very moist and too cool for any other species of squash to grow, except for some short-season landraces of C. In Shanghai a large quantity of C. They became a curiosity in European botanical gardens. This convinced the botanists of the time and for many years afterward that C. He assumed that ofertas de forex en londres para espanoles 2016 the "annual" species were of Old World origin.
The most frequently used vernacular name for C. The names used in Bolivia, Peru, and northern Argentina, in the Quechua and Aymara language areas, are surprisingly similar if not identical to the Mexican names: The etymological evidence is inconclusive at best in this regard The Nahuatl names could be derived from or precede the similar sounding Quechuan and Aymara names. He speculated that the Nahuatl name, tzilacayotliis derived from either the words tzilac-ayotlimeaning "smooth calabaza or squash", or tzilictic-ayotlimeaning "squash that resonates or sounds" when struck.
The name cuicuilticayotli literally means the "painted squash". The bowl was placed in front of the image or images, and with their marbled appearance, were said to be made of precious stones which the Aztecs called chalchihuitl.
This religious practice suggests an ancient use, if not origin, in Mexico and subsequent spread to the south. The archaeological record tells a different story. Numerous seed remnants and pedicels of C. These have been recovered from several horizons spanning several ofertas de forex en londres para espanoles 2016 years, beginning from a pre-ceramic, pre-maize horizon ofertas de forex en londres para espanoles 2016 at B.
In contrast, no definitive archaeological specimen of C. A single seed, recovered from the Valley of Oaxaca, dated at A. Despite the archaeological record, C. This conclusion is based on several lines of circumstancial evidence in addition to that already mentioned and suggests a pattern of dispersal evident in the often closely associated crops maize, beans, and the squash species, C.
On the basis of the estimated time taken for C. He concluded from this that C. He did not consider the possibility that these archaeological squashes were not autochthonous but were instead brought down from farms at higher altitudes. Agriculture was initially of lesser importance in the lowlands than at the higher elevations. The earliest archaeological seeds of C. These bees depend almost exclusively on squash flowers for pollen and nectar for themselves and their larvae, and therefore appear to have coevolved with the cucurbits.
The center of diversity of these bees occurs in southern Mexico, where the greatest concentration of Cucurbita species is located. There is one species of squash bee, P. There are other more generalized species of squash and gourd bees, which occur throughout the Americas and use the pollen of all the cultivated species of squash, including C.
The absence of P. This is based on the assumption that P. Before reaching a definitive conclusion about human dispersal of C. Peponapis atrata may not be as monolectic as reported in the literature; a female P. Andres and species determined by W. The hypothesis resulting from the squash and gourd bee study of Hurd et al. While they are derived from extensive field observations, they have not been tested experimentally.
The study did not demonstrate whether the various species of bees coevolved with specific species of Cucurbita or with the genus in general. The latter is the rule among oligolectic bees G.
The fact that these bees and Cucurbita species share centers of diversity may not be due to their coevolution but rather to other causes such as their independent adaptation to the extreme habitat diversity of the region.
Experimental tests need to be conducted to determine if species such as P.