Helianthus

Sunflower field (Helianthus annuus )

The sunflower (Helianthus ) constitute a genus in the subfamily of herbaceous within the sunflower family ( Asteraceae). The home of all about 67 species North America.

In Central Europe, two species are cultivated as important: the actual sunflower ( Helianthus annuus ) and Jerusalem artichoke ( Helianthus tuberosus ).

Description

Vegetative characteristics

The species of the genus Helianthus are an annual or perennial herbaceous plants with plant height between ( 5) and 20 300 (500 ) cm. A few species form Rhizomknollen as outlasting. The stalk ( stem axis ) is directed upward or ascending to decumbent, or countertop. Only at the upper end starts branching of the stems.

The leaves are only basally or distributed on the whole stems, opposite -employed and / or alternate. They are stalked or sessile. The leaf blade is usually three annoying eggertii only in Helianthus, Helianthus Helianthus smithii and maximilliani also einnervig. Usually the leaf blade is triangular, lanceolate - linear, lanceolate - ovate, linear or ovate in shape. The leaf base is heart-shaped or narrowly wedge-shaped. The leaf margin lobed usually entire or dentate, rarely. The leaf surfaces may be glabrous or hairy, often glandular spotted.

Inflorescences and flowers

The flower baskets are available individually or together in more or less doldentraubigen, doldenrispigen aged men or groups. In the basket- shaped inflorescence has both tube and ray florets. The involucre ( = involucre ) ( calyx is misleading here, because it is not a part of the flower, so do not calyx but a part of the inflorescence ) is more or less hemispherical, sometimes bell-shaped or cylindrical. It has a diameter of 5 to 40 mm or more, wherein the cultured agents, more than 200 mm can be achieved. The bracts are persistent, ever bloom there are eleven to 40 ( or more than 100 for engineered products) are available in two, three or more rows that are similar to each other almost or are designed equal. The inflorescence base is flat to slightly convex, only in Heliantus porteri he is conical. He is busy with chaff leaves that are more or less folded lengthwise, have a rectangular - elongated shape and have three teeth or occasionally entire. Sometimes the tips are reddish or purple. It is outside a range of five to 30 or more ( or breeds over 100 ) zygomorphic ray florets ( ray florets = ) formed rarely be absent. They are barren, the Roehrig fused petals are usually yellow. The number of tubular flowers with radial symmetry ( = disc florets ) is between (15 ) 30 and more than 150 varieties also in 1000. You are hermaphrodite, fertile, the petals reddish yellow or at least at the top. The corolla tube is always shorter than the bell-shaped Kronschlund, who has five triangular Corolla lobe. The branches of the style are slim, the attachments are still more or less pointed.

Infructescences and fruits

The achenes are usually purple-black, sometimes mottled, more or less reversed pyramid -shaped and depressed. In Helianthus porteri no pappus is present in other species, the daddy fall off easily. Usually they are on 2 or 3 lanceolate, awned or irregularly serrated bristles that have a length of 1 to 5 mm. In addition, it is up to eight shorter flakes having a length of 0.2 to 2 mm.

Other features

The base chromosome number is.

System

In the genus sunflowers ( Helianthus ), there are about 52 to 67 species:

  • H. agrestis
  • H. ambiguus
  • H. angustifolius
  • H. anomalus
  • Sunflower ( H. annuus )
  • H. argophyllus
  • H. arizonensis
  • H. atrorubens
  • H. bolanderi
  • H. californicus
  • H. carnosus
  • H. ciliaris
  • H. cinereus
  • H. couplandii
  • H. cucumerifolius
  • H. cusickii
  • H. debilis
  • H. decapetalus
  • H. divaricatus
  • H. divariserratus
  • H. doronicoides
  • H. eggertii
  • H. floridanus
  • H. giganteus
  • H. glaucophyllus
  • H. gracilentus
  • H. grosseserratus
  • H. heterophyllus
  • H. hirsutus
  • H. intermedius
  • H. kellermanii
  • H. laciniatus
  • H. laetiflorus
  • H. laevigatus
  • H. longifolius
  • H. luxurians
  • H. maximiliani
  • H. microcephalus
  • H. mollis
  • H. multiflorus
  • H. neglectus
  • H. niveus
  • H. nuttallii
  • H. occidentalis
  • H. orgyaloides
  • H. paradoxus
  • H. pauciflorus
  • H. petiolaris
  • H. porteri
  • H. praecox
  • H. praetermissus
  • H. pumilus
  • H. radula
  • H. resinosus
  • H. rigidus
  • H. salicifolius
  • H. schweinitzii
  • H. silphioides
  • H. simulans
  • H. smithii
  • H. strumosus
  • Jerusalem artichoke ( H. tuberosus )
  • H. verticillatus
Asteroideae Heliantheae Rhizome Pappus (flower structure)
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