Browsing by Subject "inflorescence"

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  • Othmani, Ahmed; Collin, Myriam; Sellemi, Amel; Jain, Shri Mohan; Drira, Noureddine; Aberlenc, Frederique (2017)
    The date palm (Phoenix dactylifera L.) is dioecious with male flowers deficient in functional gynoecium and female flowers deficient in functional androecium borne on separate palms. The presence of male and female flowers on the same plant, a phenomenon known as monoecy, is unusual in male date palms. This study reports for the first time on hermaphrodite (bisexual) flowers borne by two female date palms, 'Alligue', that were found growing in an open field in Degache, southern Tunisia. The observations on these two female palms were compared with hermaphrodite male date palms growing in the same location. Hermaphrodite female date palm inflorescence branches bear female flowers predominantly near their base, in contrast to the hermaphrodite flowers that are found primarily toward their upper part. The position of the hermaphrodite flowers in hermaphrodite male date palms is reversed: inflorescence branches bear male flowers toward the upper part while the hermaphrodite flowers are found at the base. Histological examination of female hermaphrodite flowers revealed that they had three carpels and 1-6 stamens. Hermaphrodite flowers on male plants were usually also composed of three carpels of variable size, and six stamens. Hermaphrodite flowers on both female and male palm trees turn generally into parthenocarpic fruits. The present data support the theory that dioecious plants are derived from a common hermaphrodite ancestor. Floral hermaphroditism in date palm should be investigated in relation to the in planta self-fertilization process to identify sex markers and genes that control sex organ development.
  • Juntheikki-Palovaara, Inka; Tahtiharju, Sari; Lan, Tianying; Broholm, Suvi K.; Rijpkema, Anneke S.; Ruonala, Raili; Kale, Liga; Albert, Victor A.; Teeri, Teemu H.; Elomaa, Paula (2014)
  • Cai, Xiaobo (Helsingin yliopisto, 2020)
    Inflorescence meristems (IMs) either keep producing new flowers, thereby being indeterminate, or terminate after initiation of a finite number of flowers, thereby being determinate. Gerbera hybrida (Asteraceae) has determinate inflorescences. It has been found that the LEAFY (LFY) homolog GhLFY and SEPALLATA (SEP)-like GRCD2/7 promote IM termination in Gerbera as LFY and SEP genes do in Arabidopsis. Downregulation of their expression in Gerbera leads to indeterminate inflorescences. Considering the roles of WUSCHEL (WUS), CLAVATA3 (CLV3) and SHOOT MERISTEMLESS (STM) in meristem maintenance and of TERMINAL FLOWER 1 (TFL1) in IM determinacy in Arabidopsis, it is possible that GhLFY and GRCD2/7 contribute to IM termination by regulating the expression of the homologs of these genes, namely GhWUSb, GhWOX2a, GhCLV3, GhSTM and GhTFL1. It is also possible that GhLFY upregulates the expression of GRCD2/7 in Gerbera, since LFY upregulates SEP gene expression in Arabidopsis. To test these hypotheses, the expression of these candidate genes in Gerbera IMs was compared between IM-expanding and terminating stages, as well as between transgenic plants with downregulated GhLFY or GRCD2/7 expression and wild-type plants. In addition, the pOpOn2 inducible expression vector was used in Gerbera for the first time, in order to induce GhWUSb overexpression in transgenic plants and to study the function of GhWUSb in IM determinacy. Expression analysis showed that during IM termination, GRCD7 expression was upregulated, while the expression of GhWUSb, GhCLV3 and GhWOX2a was downregulated. GhLFY upregulated the expression of GRCD7, and both of them downregulated the expression of GhWUSb, GhCLV3 and GhWOX2a. The expression of GhSTM and GRCD2 was neither affected by IM termination nor regulated by GhLFY or GRCD7. GhTFL1 expression was not detected in any IM samples. Induced GhWUSb overexpression delayed IM termination, confirming the role of GhWUSb in meristem maintenance. These results suggest that GRCD7 may contribute to IM termination by suppressing the expression of the meristem maintenance gene GhWUSb, and the upregulation of GRCD7 by GhLFY may be required for IM termination. GRCD2 and GhSTM may not play a significant role in inflorescence determinacy.