Comparative Ontogeny of Hermaphrodite and Pistillate Florets in Helianthus annuus L. (Asteraceae)

• Main Authors: Aslıhan ÇETİNBAŞ, Meral ÜNAL
• Format: Article
• Language: English
• Published: University of Agricultural Sciences and Veterinary Medicine, Cluj-Napoca 2012-05-01
• Series: Notulae Scientia Biologicae
• Online Access: http://notulaebiologicae.ro/index.php/nsb/article/view/7576

<span style="font-family: Times New Roman; font-size: small;"> </span><p style="margin: 0in 0in 0pt; text-align: justify;" class="MsoNormal"><span style="font-family: Times New Roman;"><span lang="EN-US" style="color: #221e1f; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">The </span><span lang="EN-US" style="color: black; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">inflorescence of <span style="mso-bidi-font-style: italic;">Helianthus annuus </span>L. has two types of flowers (or florets) on a single capitulum; central </span><span lang="EN-US" style="color: #221e1f; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">hermaphrodite </span><span lang="EN-US" style="color: black; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">disc florets and peripheral pistillate ray florets. In both florets, reproductive development starts with the conversion of apical meristem into floral meristem that will produce floral organ primordia. The only difference between hermaphrodite and pistillate florets in apical meristem stage is that apical meristem of the pistillate florets is not as apparent and curvaceous as apical meristem of the hermaphrodite florets. </span><span lang="EN-US" style="color: #221e1f; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">The differentiation of apical meristem into floral meristem is in the same progress in both florets. </span><span lang="EN-US" style="color: black; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">In hermaphrodite florets, flower organs; petals, stamens and carpels develop from floral meristem. </span><span lang="EN-US" style="color: #221e1f; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">Differentiation of five petal primordia takes place in the same way in both florets. </span><span lang="EN-US" style="color: black; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">Firstly filament and then anther differentiates in a stamen. Two carpel primordia appear below the stamen primordia in hermaphrodite florets. In following stages, carpel primordia are lengthened and formed inferior ovary, style, stigma respectively. In pistillate florets, flower organs; petals and carpels develop from floral meristem. They pass </span><span lang="EN-US" style="color: #221e1f; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">directly from the periant initiation to the start of carpel formation. </span><span lang="EN-US" style="color: black; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">Stamen primordia don’t appear and the further development of </span><span lang="EN-US" style="color: #221e1f; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">carpel primordia stops in a short time, as a result, stigma and style do not exist </span><span lang="EN-US" style="color: black; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">in pistillate florets</span><span lang="EN-US" style="color: #221e1f; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">. However, an inferior ovary with no ovule forms. In the capitulum of </span><span lang="EN-US" style="color: black; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">hermaphrodite florets, t</span><span lang="EN-US" style="color: #221e1f; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">he </span><span lang="EN-US" style="color: black; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">development takes place in a centripetal manner</span><span lang="EN-US" style="color: #221e1f; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">; it </span><span lang="EN-US" style="color: black; font-size: 10pt; mso-bidi-font-family: &quot;Garamond Premr Pro Subh&quot;;">starts firstly on the outermost whorl, and it proceeds towards inner whorl. However, this is not the case in pistillate florets.</span><span lang="EN-US"></span></span></p><span style="font-family: Times New Roman; font-size: small;"> </span>