Flowering cross-pollination

When the pollen is transferred to the stigma of its own flower the process is called Close or Self-pollination) if to a stigma of another flower. Cross-pollination. If fertilization follows, these processes are termed respectively, Close or Self-fertilization and Cross-fertilization. Close-fertilization means in time ruination to the race and happily is prevented in many cases by (a) the stamens and pistils standing in extraordinary relation to each other, (b) by the anthers and pistils maturing at different times, (c) by the pollen in many cases germinating better on the stigma of another flower than its own. 

The viability of seeds produced by S. divinorum is questionable. It is apparently a self-sterile plant which will produce seed only when cross-pollinated (1). Valdes pollinated fourteen flowers and four produced seeds. Unfortunately, the seeds viability could not be assessed as they were accidentally killed when a growth chamber overheated (1). Generally, this plant is reproduced by cuttings. It is a diploid species (N=l 1) whose pollen grains are not as viable as those of other Salvia species. Out of 3027 pollen grains, Reisfield found that 53% aborted, although this fact alone does not explain why the plants do not set seed in Mexico (16). Even when 5. divinorum is hand pollinated, only 2 to 3 percent of the nutlets fully mature (8). 

Further resolution of the problem was obtained by studying pollen germination and tube growth through styles of hand-pollinated flowers. Of 39 styles observed, 13 (33%) had four or more pollen tubes that traversed the entire length of the style, reaching the ovary. Three or more pollen tubes reached the ovary in almost one half the styles observed. Of the 20 styles in which four or more pollen grains or tubes were observable at all, 14 had three or more pollen tubes that reached the ovary. Also, no difference was noted between the self- and supposed cross-pollinations. 

Cross-pollination pollen is delivered to a flower of a different individual of... 

Pollination of Helianthus species is predominantly by honeybees and bumblebees (Cockerell, 1914), although other insects may be active. Helianthus are all-day flowers, presenting a continuous pollen and nectar resource for bees and other insects. Jerusalem artichoke, like nearly all Helianthus species, is largely self-incompatible, and as a consequence, cross-pollination is essential for the production of viable seed, with self-pollination being a rare event. 

Insects are so successful because of their mobility, high reproductive potential, ability to exploit plants as a food resource, and to occupy so many ecological niches. Plants are essentially sessile and can be seen to produce flowers, nector, pollen, and a variety of chemical attractants to induce insect cooperation in cross-pollination. However, in order to reduce the efficiency of insect predation upon them, plants also produce a host of structural, mechanical, and chemical defensive artifices. The most visible chemical defenses are poisons, but certain chemicals, not intrinsically toxic, are targeted to disrupt specific control systems in insects that regulate discrete aspects of insect physiology, biochemistry, and behavior. Hormones and pheromones are unique regulators of insect growth, development, reproduction, diapause, and behavior. Plant secondary chemicals focused on the disruption of insect endocrine and pheromone mediated processes can be visualized as important components of plant defensive mechanisms. 

Sunflower is a highly cross-pollinated crop. Wild sunflowers have several flowers or heads and depend on the work of insects for pollination. Wild sunflowers are the genetic base of current commercial sunflowers of a single flower or head per plant. 

Modifications in the characteristics of sunflower are obtained through crosses to recombine genes from two sexually compatible parents. Both for self pollination and for controlled crosses, it is important that heads be isolated before flowering to avoid natural cross-pollination. 

To flourish and bear well, citrus trees require a site with excellent drainage and full sun. Prune to remove dead wood, to keep trees in bounds, and to thin out centers where growth is too dense. Citrus flowers attract bees don t plant them in high-traffic areas. Citrus trees bear fruit without cross-pollination. 

Walnuts are large, deciduous trees bearing separate male and female flowers on the same plant. To get the heaviest nut production, plant 2 different cultivars for cross-pollination. The most commonly grown types are black walnut Julians nigra) and English walnut... 

It is not yet known whether the emission ofterpenes from A. thaliana flowers is directly responsible for the attraction of these insects (as well as the efficacy of the insects in cross-pollinating the flowers). Such investigations should include GC-electroantennograms monitoring the antennal response to distinct terpene compounds of the volatile blend, and wind tunnel experiments with insect species shown to have visited the A. thaliana flowers. In addition, it will be useful to determine Che cross-pollination rates in synthetic populations of various Arahidopxis ecotypes and TPS mutant lines lacking or overproducing one or several floral terpene compounds. 

The structure of plant (monoic or dioic) varies to the size and anatomic and physiological characterists of flower and their position in the plant, may occur the autopollination or cross pollination. This cross pollination provides a rise in gene flow between plants, spreading them and the results are favorable (Malerbo-Souza et al., 2004). 

Plants, year by year, specialized in attract more efficient pollinators and make transportation of their reproductive cells, and therewith could be benefited with cross pollination. The disposition of flowers is an important factor that can be isolated in the branches or grouped in the same floral axis forming inflorescence, colour, odour, size, nectar, oil, pollen and... 

The floral rewards provided by Angiosperms are required to attract peUinators, nectar seems the most searched in crop cultivated commercially, however, in searching by this reward many animals, mainly worker honeybees Apis mellifera have pwllen adhered to their body, and so, later deposit accidentally their loads on the stigma of other flower of the same specie, performing indirectly the cross pollination. 

The botanical name of sunflower is Hdianihus annuus, a predominantly cross-pollinated [3] species of the Asteraceae family. Sunflowers are annual crops with a height of up to 300 cm and a distinguishing, 15-30-cm diameter head. This inflorescence is composed of yellow flowers forming an outer ring and a brown inner... 

Solanum tuberosum is a species of the Solanaceae family. The pereimial, cross-pollinated plant reaches a height of about 80 cm and develops white or purple flowers and a thick characteristic tuber. The tuber has a starch content of about 15% (fresh matter) consisting of 79% amylopectin and 21% amylose [10]. 

The most reliable mechanism of blocking self-pollination and favoring cross-pollination is separation of female and male generative organs and their formation on various plants (on separate male (staminate) or female (pistillate) individuals) or at a certain distance on the same plant. Such plants as date palm, dioecious hemp, spinach, hop, buckthorn, some nuciferous plants, etc. develop female and male flowers on different individuals. This is the reason why they are called dioecious plants. Male and female flowers of monoecious plants are located on the same plant but at some distance com, watermelon, cucirmbers, coco palm, walnut, hazelnut and other crops are the examples. The mrmber of monoecious plants is large 10% of all mono- and 4% of all dicotyledonous plants. 

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