Editing Cucurbita (section)

== Description ==

''Cucurbita'' species fall into two main groups. The first group consists of [[annual plant|annual]] or short-lived [[perennial plant|perennial]] vines which are [[mesophyte|mesophytic]], meaning they require a more or less continuous water supply. The second group are [[perennial plant|perennials]] growing in arid zones which are [[xerophyte|xerophytic]], meaning they tolerate dry conditions. Cultivated ''Cucurbita'' species were derived from the first group. Growing {{convert|5|to|15|m|ft|round=5|abbr=off|sp=us}} in height or length, the plant stem produces [[tendril]]s to help it climb adjacent plants and structures or extend along the ground. Most species do not readily root from the nodes; a notable exception is ''C.&nbsp;ficifolia'', and the four other cultivated mesophytes do this to a lesser extent. The vine of the perennial ''Cucurbita'' can become semiwoody if left to grow. There is wide variation in size, shape, and color among ''Cucurbita'' fruits, and even within a single species. ''C.&nbsp;ficifolia'' is an exception, being highly uniform in appearance.<ref name="nee">{{cite journal | last1 = Nee | first1 = Michael | year = 1990 | title = The Domestication of ''Cucurbita'' (Cucurbitaceae) | journal = [[Economic Botany]] | volume = 44 | issue = 3, Supplement: New Perspectives on the Origin and Evolution of New World Domesticated Plants | pages = 56–68 | publisher = New York Botanical Gardens Press | location = New York | jstor = 4255271| doi = 10.1007/BF02860475 | bibcode = 1990EcBot..44S..56N | s2cid = 40493539 }}</ref> The [[Morphology (biology)|morphological]] variation in the species ''C.&nbsp;pepo''<ref name="deckerwalters">{{cite journal | last1 = Decker-Walters | first1 = Deena S. | last2 = Staub | first2 = Jack E. | last3 = Chung | first3 = Sang-Min | last4 = Nakata  | first4 = Eijiro  | last5 = Quemada | first5 = Hector D. | year = 2002 | title = Diversity in Free-Living Populations of ''Cucurbita pepo'' (Cucurbitaceae) as Assessed by Random Amplified Polymorphic DNA | journal = [[Systematic Botany]] | volume = 27 | issue = 1 | pages = 19–28 | publisher = American Society of Plant Taxonomists | jstor = 3093892 }}</ref> and ''C.&nbsp;maxima''<ref name="maximadiffspecies">{{cite journal|last=Millán|first=R.|title= Variaciones del Zapallito Amargo ''Cucurbita andreana'' y el Origen de ''Cucurbita maxima''|journal=Revista Argentina de Agronomía|year=1945|volume= 12|pages=86–93|language=es}}</ref> is so vast that its various [[subspecies]] and cultivars have been misidentified as totally separate species.<ref name="deckerwalters" />

The typical cultivated ''Cucurbita'' species has five-lobed or [[Leaf shape|palmately divided]] leaves with long [[Petiole (botany)|petioles]], with the leaves alternately arranged on the stem. The stems in some species are angular. All of the above-ground parts may be hairy with various types of [[trichome]]s, which are often hardened and sharp. Spring-like tendrils grow from each [[Plant stem|node]] and are branching in some species. ''C.&nbsp;argyrosperma'' has ovate-cordate (egg-shaped to heart-shaped) leaves. The shape of ''C.&nbsp;pepo'' leaves varies widely. ''C.&nbsp;moschata'' plants can have light or dense [[Leaf#Surface|pubescence]]. ''C.&nbsp;ficifolia'' leaves are slightly angular and have light pubescence. The leaves of all four of these species may or may not have white spots.<ref name="saade" />

The species are [[monoecious]], with unisexual male ([[stamen|staminate]]) and female ([[pistil]]late) flowers on a single plant and these grow singly, appearing from the [[Axillary bud|leaf axils]]. Flowers have five fused yellow to orange petals (the [[petal#Corolla|corolla]]) and a green bell-shaped [[Sepal|calyx]]. Male flowers in Cucurbitaceae generally have five stamens, but in ''Cucurbita'' there are only three, and their [[anther]]s are joined so that there appears to be one.<ref name="Mabberley">{{cite book |last=Mabberley |first=D. J. |year=2008 |title=The Plant Book: A Portable Dictionary of the Vascular Plants |publisher=Cambridge University Press |location=Cambridge |isbn=978-0-521-82071-4 |page=235}}</ref><ref name="eflora">{{cite web |last1=Lu |first1=Anmin |last2=Jeffrey |first2=Charles |work=Flora of China |title=''Cucurbita'' Linnaeus |url=http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=108644 |access-date=February 21, 2015 |archive-date=September 6, 2015 |archive-url=https://web.archive.org/web/20150906013041/http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=108644 |url-status=live }}</ref> Female flowers have thick [[Pedicel (botany)|pedicels]], and an [[inferior ovary]] with 3–5 [[Stigma (botany)|stigmas]] that each have two lobes.<ref name="saade" /><ref name="ucla" /> The female flowers of ''C.&nbsp;argyrosperma'' and ''C.&nbsp;ficifolia'' have larger corollas than the male flowers.<ref name="saade" /> Female flowers of ''C.&nbsp;pepo'' have a small calyx, but the calyx of ''C.&nbsp;moschata'' male flowers is comparatively short.<ref name="saade" />

''Cucurbita'' fruits are large and fleshy.<ref name=Mabberley/> Botanists classify the ''Cucurbita'' fruit as a [[Berry (botany)#Modified berries|pepo]], which is a special type of [[Berry (botany)|berry]] derived from an inferior ovary, with a thick outer wall or rind with [[hypanthium]] tissue forming an [[exocarp]] around the ovary, and a fleshy interior composed of [[mesocarp]] and [[endocarp]]. The term "pepo" is used primarily for Cucurbitaceae fruits, where this fruit type is common, but the fruits of ''[[Passiflora]]'' and ''[[Carica]]'' are sometimes also pepos.<ref name="hypanthium">{{cite web |url=http://www.worldbotanical.com/fruit_types.htm |title=A Systematic Treatment of Fruit Types |publisher=Worldbotanical |access-date=October 10, 2013 |archive-date=July 13, 2017 |archive-url=https://web.archive.org/web/20170713022453/http://www.worldbotanical.com/fruit_types.htm |url-status=live }}</ref><ref name="schrager">{{cite book |last=Schrager|first=Victor |title=The Compleat Squash: A Passionate Grower's Guide to Pumpkins, Squash, and Gourds |publisher=Artisan |location=New York |year=2004 |page=25 |isbn=978-1-57965-251-7}}</ref> The seeds, which are attached to the ovary wall (parietal placentation) and not to the center, are large and fairly flat with a large embryo that consists almost entirely of two [[cotyledon]]s.<ref name="ucla" /> Fruit size varies considerably: wild fruit specimens can be as small as {{convert|4|cm|in|frac=2|abbr=off|sp=us}} and some domesticated specimens can weigh well over {{convert|300|kg|lb|abbr=off|sp=us}}.<ref name="saade" /> The current world record was set in 2014 by Beni Meier of [[Switzerland]] with a {{convert|2323.7|lb|kg|0|abbr=on|adj=on|order=flip}} pumpkin.<ref name="appumpkin">{{cite news |title=2014 – Beni Meier and his 2323.7 pound World Record Giant Pumpkin! |url=http://www.bigpumpkins.com/ViewArticle.asp?id=186&gid=62 |publisher=BigPumpkins.com |access-date=February 12, 2016 |date=2014 |archive-date=March 4, 2016 |archive-url=https://web.archive.org/web/20160304025635/http://www.bigpumpkins.com/ViewArticle.asp?id=186&gid=62 |url-status=live }}</ref>

<gallery widths="200" heights="160">
File:Cucurbita moschata leaves.jpg|The leaves of ''[[Cucurbita moschata]]'' often have white spots near the veins.
File:Cucurbita 2011 G1 Large.jpg|Two bright orange ''C. pepo'' pumpkins, centre right; the rest are squashes, ''C. maxima''
</gallery>

=== Reproductive biology ===

[[File:Peponapis pruinosaCane-12.JPG|thumb|alt=Bee pollinating female ''Cucurbita'' flower|''Cucurbita'' female flower with pollinating [[squash bee]]s]]

All species of ''Cucurbita'' have 20 pairs of [[chromosome]]s.<ref name="rhodes">{{cite journal |last1=Rhodes |first1=A. M. |last2=Bemis |first2=W. P. |last3=Whitaker |first3=Thomas W. |last4=Carmer |first4=S. G. |year=1968 |title=A Numerical Taxonomic Study of ''Cucurbita'' |journal=[[Brittonia]] |publisher=[[New York Botanical Garden Press]] |volume=20 |issue=3 |pages=251–266 |doi=10.2307/2805450 |jstor=2805450 |bibcode=1968Britt..20..251R |s2cid=6973668}}</ref>

Many North and Central American species are visited by specialist [[pollinator]]s in the [[Apidae|apid]] tribe [[Eucerini]], especially the genera ''[[Peponapis]]'' and ''[[Xenoglossa]]'', and these [[squash bee]]s can be crucial to the flowers producing fruit after pollination.<ref name="nee" /><ref name="hurd">{{cite journal |last1=Hurd |first1=Paul D. |last2=Linsley |first2=E. Gorton |year=1971 |title=Squash and Gourd Bees (''Peponapis'', ''Xenoglossa'') and the Origin of the Cultivated ''Cucurbita'' |journal=[[Evolution (journal)|Evolution]] |location=St. Louis, MO |publisher=Society for the Study of Evolution |volume=25 |issue=1 |pages=218–234 |doi=10.2307/2406514 |jstor=2406514 |pmid=28562933}}</ref><ref name="whitbem">{{cite journal |last1=Whitaker |first1=Thomas W. |last2=Bemis |first2=W. P. |year=1964 |title=Evolution in the Genus ''Cucurbita'' |journal=Evolution |volume=18 |issue=4 |pages=553–559 |doi=10.2307/2406209 |jstor=2406209}}</ref>

[[File:Cucurbita maxima Zapallo Plomo semillería Costanzi - flowers detail (masculine) - male flower, some petals and 1 filament removed.jpg|thumb|120px|alt=Male ''Cucurbita'' flower|Male flower, part of the perianth removed, arrows indicating nectar pores]]

When there is more pollen applied to the stigma, more seeds are produced in the fruits and the fruits are larger with greater likelihood of maturation,<ref name="winsor">{{Cite journal |last1=Winsor |first1=J. A. |last2=Davis |first2=L. E. |last3=Stephenson |first3=A. G. |year=1987 |title=The Relationship Between Pollen Load and Fruit Maturation and the Effect of Pollen Load on Offspring Vigor in ''Cucurbita pepo'' |journal=The American Naturalist |volume=129 |issue=5 |pages=643–656 |doi=10.1086/284664 |jstor=2461727 |s2cid=84901190}}</ref> an effect called [[xenia (plants)|xenia]]. Competitively grown specimens are therefore often hand-pollinated to maximize the number of seeds in the fruit.<ref name="rwrobinsoncross">{{cite journal |last=Robinson |first=Richard W. |year=2000 |title=Rationale and Methods for Producing Hybrid Cucurbit Seed |journal=Journal of New Seeds |volume=1 |issue=3–4 |pages=1–47 |doi=10.1300/J153v01n03_01 |s2cid=85158524}}</ref><ref name="stephenson">{{cite journal |last1=Stephenson |first1=Andrew G. |last2=Devlin |first2=B. |last3=Horton |first3=J. Brian |year=1988 |title=The Effects of Seed Number and Prior Fruit Dominance on the Pattern of Fruit Production in ''Cucurbita pepo'' (Zucchini Squash) |journal=Annals of Botany |volume=62 |issue=6 |pages=653–661 |doi=10.1093/oxfordjournals.aob.a087705}}</ref> [[Parthenocarpy|Seedlessness]] is known to occur in certain cultivars of ''C.&nbsp;pepo''.<ref name="robinsonreiners">{{cite journal |last1=Robinson |first1=R. W. |last2=Reiners |first2=Stephen |date=July 1999 |title=Parthenocarpy in Summer Squash |url=http://hortsci.ashspublications.org/content/34/4/715.full.pdf |url-status=live |journal=HortScience |volume=34 |issue=4 |pages=715–717 |doi=10.21273/HORTSCI.34.4.715 |archive-url=https://web.archive.org/web/20151106115239/http://hortsci.ashspublications.org/content/34/4/715.full.pdf |archive-date=2015-11-06 |access-date=2013-11-07 |doi-access=free}}</ref><ref name="menezes">{{cite journal |last1=Menezes |first1=C. B. |last2=Maluf |first2=W. R. |last3=Azevedo |first3=S. M. |last4=Faria |first4=M. V. |last5=Nascimento |first5=I. R. |last6=Gomez |first6=L. A. |last7=Bearzoti |first7=E. |date=March 2005 |title=Inheritance of Parthenocarpy in Summer Squash (''Cucurbita pepo'' L.). |journal=Genetics and Molecular Research |volume=4 |issue=1 |pages=39–46 |pmid=15841434}}</ref>

Critical factors in flowering and fruit set are physiological, having to do with the age of the plant and whether it already has developing fruit.<ref name="stapleton">{{cite journal |last1=Stapleton |first1=Suzanne Cady |last2=Wien |first2=H. Chris |last3=Morse |first3=Roger A. |year=2000 |title=Flowering and Fruit Set of Pumpkin Cultivars under Field Conditions |journal=HortScience |volume=35 |issue=6 |pages=1074–1077 |doi=10.21273/HORTSCI.35.6.1074 |issn=0018-5345 |doi-access=free}}</ref> The [[plant hormone]]s [[ethylene]] and [[auxin]] are key in fruit set and development.<ref name="martínez">{{cite journal |last1=Martínez |first1=Cecelia |last2=Manzano |first2=Susana |last3=Megías |first3=Zoraida |last4=Garrido |first4=Dolores |last5=Picó |first5=Belén |last6=Jamilena |first6=Manuel |year=2013 |title=Involvement of Ethylene Biosynthesis and Signalling in Fruit Set and Early Fruit Development in Zucchini Squash (''Cucurbita pepo'' L.) |journal=BMC Plant Biology |volume=13 |issue=139 |pages=139 |doi=10.1186/1471-2229-13-139 |issn=1471-2229 |pmc=3856489 |pmid=24053311 |doi-access=free}}</ref> Ethylene promotes the production of female flowers. When a plant already has a fruit developing, subsequent female flowers on the plant are less likely to mature, a phenomenon called "first-fruit dominance",<ref name="stapleton" /> and male flowers are more frequent, an effect that appears due to reduced natural ethylene production within the plant stem.<ref name="krupmick">{{Cite journal |last1=Krupnick |first1=Gary A. |last2=Brown |first2=Kathleen M. |last3=Stephenson |first3=Andrew G. |year=1999 |title=The Influence of Fruit on the Regulation of Internal Ethylene Concentrations and Sex Expression in ''Cucurbita texana'' |journal=International Journal of Plant Sciences |volume=160 |issue=2 |pages=321–330 |doi=10.1086/314120 |s2cid=85794143}}</ref> [[Ethephon]], a plant growth regulator product that is converted to ethylene after metabolism by the plant, can be used to increase fruit and seed production.<ref name="rwrobinsoncross" /><ref name="murray">{{cite journal |last=Murray |first=M. |year=1987 |title=Field Applications Of Ethephon For Hybrid And Open-Pollinated Squash (''Cucurbita'' Spp) Seed Production |journal=Acta Horticulturae |volume=201 |issue=201 |pages=149–156 |doi=10.17660/ActaHortic.1987.201.15}}</ref> Although ''Cucurbita'' species can generally produce healthy fruit after pollination from the same plant, [[inbreeding depression]] can significantly reduce seed number and fruit size.<ref>{{citation |author=Inácio, Cardoso |year=2004 |title=Depression by inbreeding after four successive self-pollination squash generations |journal=Scientia Agricola |volume=61 |doi=10.1590/S0103-90162004000200016|hdl=11449/5322 |hdl-access=free }}</ref>

The plant hormone [[gibberellin]], produced in the stamens, is essential for the development of all parts of the male flowers. The development of female flowers is not yet understood.<ref name="lange">{{cite journal |last1=Pimenta Lange |first1=Maria João |last2=Knop |first2=Nicole |last3=Lange |first3=Theo |year=2012 |title=Stamen-derived Bioactive Gibberellin is Essential for Male Flower Development of ''Cucurbita maxima'' L. |journal=Journal of Experimental Botany |volume=63 |issue=7 |pages=2681–2691 |doi=10.1093/jxb/err448 |pmc=3346225 |pmid=22268154}}</ref> Gibberellin is also involved in other developmental processes of plants, such as seed and stem growth.<ref name="sturt">{{cite web |title=Plant Hormones |url=http://www.hsc.csu.edu.au/agriculture/production/3359/plant_hormones_answers.htm |url-status=dead |archive-url=https://web.archive.org/web/20140116140049/http://www.hsc.csu.edu.au/agriculture/production/3359/plant_hormones_answers.htm |archive-date=January 16, 2014 |access-date=January 15, 2014 |publisher=Charles Sturt University}}</ref>

==== Germination and seedling growth ====
[[File:Kabocha (GH) 21June2005 sown 14June.JPG|thumb|alt=Kabocha seedling at seven days age|[[Kabocha]] seedling seven days after being sown]]

Seeds with maximum [[germination]] potential develop (in ''C.&nbsp;moschata'') by 45 days after [[anthesis]], and seed weight reaches its maximum 70 days after anthesis.<ref name="wilsonma">{{Cite journal |last1=Wilson |first1=Mack A. |last2=Splittstoesser |first2=Walter E. |year=1980 |title=The Relationship Between Embryo Axis Weight and Reserve Protein During Development and Pumpkin Seed Germination |journal=Journal of Seed Technology |volume=5 |issue=2 |pages=35–41 |jstor=23432821}}</ref> Some varieties of ''C.&nbsp;pepo'' germinate best with eight hours of sunlight daily and a planting depth of {{convert|12|mm|in|frac=8|sp=us}}. Seeds planted deeper than {{convert|125|mm|in|frac=4|sp=us}} are not likely to germinate.<ref name="oliver">{{Cite journal |last1=Oliver |first1=Lawrence R. |last2=Harrison |first2=Steve A. |last3=McClelland |first3=Marilyn |year=1983 |title=Germination of Texas Gourd (''Cucurbita texana'') and Its Control in Soybeans (''Glycine max'') |journal=Weed Science |volume=31 |issue=5 |pages=700–706 |doi=10.1017/S0043174500070211 |jstor=4043694 |s2cid=182243467}}</ref> In ''C.&nbsp;foetidissima'', a weedy species, plants younger than 19 days old are not able to sprout from the roots after removing the shoots. In a seed batch with 90 percent germination rate, over 90 percent of the plants had sprouted after 29 days from planting.<ref name="horak">{{Cite journal |last1=Horak |first1=Michael J. |last2=Sweat |first2=Jonathan K. |year=1994 |title=Germination, Emergence, and Seedling Establishment of Buffalo Gourd (''Cucurbita foetidissima'') |journal=Weed Science |volume=42 |issue=3 |pages=358–363 |doi=10.1017/S0043174500076621 |jstor=4045510 |s2cid=132074382}}</ref>

Experiments have shown that when more pollen is applied to the stigma, as well as the fruit containing more seeds and being larger (the xenia effect mentioned above), the germination of the seeds is also faster and more likely, and the seedlings are larger.<ref name="winsor" /> Various combinations of mineral nutrients and light have a significant effect during the various stages of plant growth. These effects vary significantly between the different species of ''Cucurbita''. A type of stored phosphorus called [[Phytic acid|phytate]] forms in seed tissues as spherical crystalline intrusions in protein bodies called [[Globoid (botany)|globoids]]. Along with other nutrients, phytate is used completely during seedling growth.<ref name="beecroft">{{cite journal |last1=Beecroft |first1=Penny |last2=Lott |first2=John N. A. |year=1996 |title=Changes in the Element Composition of Globoids From ''Cucurbita maxima'' and ''Cucurbita andreana'' Cotyledons During Early Seedling Growth |journal=Canadian Journal of Botany |volume=74 |issue=6 |pages=838–847 |doi=10.1139/b96-104|bibcode=1996CaJB...74..838B }}</ref> [[Heavy metal (chemistry)|Heavy metal]] contamination, including [[cadmium]], has a significant negative impact on plant growth.<ref name="subin">{{cite journal |last1=Subin |first1=M. P. |last2=Francis |first2=Steffy |year=2013 |title=Phytotoxic Effects of Cadmium on Seed Germination, Early Seedling Growth and Antioxidant Enzyme Activities in ''Cucurbita maxima'' Duchesne |journal=International Research Journal of Biological Sciences |volume=2 |issue=9 |pages=40–47 |doi=10.1139/b96-104|bibcode=1996CaJB...74..838B }}</ref> ''Cucurbita'' plants grown in the spring tend to grow larger than those grown in the autumn.<ref name="fenner2">{{cite journal |last1=Fenner |first1=G. P. |last2=Patteron |first2=G. W. |last3=Lusby |first3=W. R. |year=1989 |title=Developmental Regulation of Sterol Biosynthesis in ''Cucurbita maxima'' L. |journal=Lipids |volume=24 |issue=4 |pages=271–277 |doi=10.1007/BF02535162 |s2cid=37220982}}</ref>