Inbotany andhorticulture,parthenocarpy is the natural or artificially inducedproduction offruit withoutfertilisation ofovules, which makes the fruit seedless. The phenomenon has been observed since ancient times[1] but was first scientifically described by German botanistFritz Noll in 1902.[2]
Stenospermocarpy may also produce apparentlyseedless fruit, but the seeds are actually aborted while they are still small. Parthenocarpy (or stenospermocarpy) occasionally occurs as a mutation in nature; if it affects every flower, the plant can no longersexually reproduce[citation needed] but might be able to propagate byapomixis or byvegetative means. Examples of this include many citrus varieties that undergonucellar embryony for reproduction, instead of solely sexual reproduction, and can yield seedless fruits.
Parthenocarpy of some fruits on a plant may be of value. Up to 20% of the fruits of wildparsnip are parthenocarpic. The seedless wild parsnip fruit are preferred by certain herbivores and so serve as a "decoy defense" againstseed predation.[3]Utah juniper has a similar defense against bird feeding.[4] The ability to produce seedless fruit whenpollination is unsuccessful may be an advantage to a plant because it provides food for the plant's seed dispersers. Without a fruit crop, the seed dispersing animals may starve or migrate.
In some plants, pollination or another stimulation is required for parthenocarpy, termedstimulative parthenocarpy. Plants that do not require pollination or other stimulation to produce parthenocarpic fruit havevegetative parthenocarpy. Seedlesscucumbers are an example of vegetative parthenocarpy, seedlesswatermelon is an example of stenospermocarpy as they are immature seeds (aborted ones).
Plants that moved from one area of the world to another may not always be accompanied by their pollinating partner, and the lack ofpollinators has spurred human cultivation of parthenocarpic varieties.
Seedlessness is seen as a desirable trait in edible fruit with hard seeds such asbanana,pineapple,orange andgrapefruit. Parthenocarpy is also desirable in fruit crops that may be difficult to pollinate or fertilize, such asfig,tomato and summersquash. Indioecious species, such aspersimmon, parthenocarpy increases fruit production because staminate trees do not need to be planted to provide pollen. Parthenocarpy is undesirable in nut crops, such aspistachio, for which the seed is the edible part. Horticulturists have selected and propagated parthenocarpiccultivars of many plants, includingbanana,fig, cactus pear (Opuntia),breadfruit andeggplant. Some plants, such as pineapple, produce seedless fruits when a single cultivar is grown because they are self-infertile. Somecucumbers produce seedless fruit ifpollinators are excluded. Seedless watermelon plants are actually grown from seeds. The seeds are produced by crossing a diploid parent with a tetraploid parent to producetriploid seeds. It has been suggested that parthenocarpy could explain the difference in the yields inactive compounds of the genusCannabis.[5][6]
Some parthenocarpic cultivars are of ancient origin. The oldest known cultivated plant is a parthenocarpic fig that was first grown at least 11,200 years ago inJordan Valley.[7]
In some climates, normally-seededpear cultivars produce mainly seedless fruit for lack of pollination.[8]
When sprayed on flowers, any of theplant hormonesgibberellin,auxin andcytokinin could stimulate the development of parthenocarpic fruit. That is termedartificial parthenocarpy. Plant hormones are seldom used commercially to produce parthenocarpic fruit. Home gardeners sometimes spray their tomatoes with an auxin to assure fruit production.[9]
Some parthenocarpic cultivars have been developed asgenetically modified organisms.[10][11]
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