Penelitian dilakukan untuk mengetahui variasi bunga Hibiscus rosa-sinensis L. bentuk crested di alam, serta hubungannya dengan ekspresi gen MADS-box. Sebanyak 200 sampel bunga crested diamati secara morfologi melalui pengukuran panjang staminal column, perhitungan perhiasan bunga, dan pengamatan visual permukaan luar ovarium. Sebanyak 137 sampel bunga crested diamati secara anatomi melalui pengamatan visual struktur internal ovarium. Hasil pengamatan morfologi dan anatomi menunjukkan tingginya variasi bunga H. rosa-sinensis bentuk crested. Salah satu karakter yang menentukan tingginya variasi bunga crested di alam adalah keberadaan petal tambahan yang diduga tumbuh di lokasi keberadaan stamen dan petal akibat gejala homeosis. Homeosis pada bunga crested diduga karena tidak terekspresikannya gen C yang merupakan salah satu kelas dari gen MADS-box. Untuk membuktikan dugaan tersebut, dilakukan pengamatan molekular melalui analisis gen MADS-box yang berperan dalam proses pembungaan. Dari kelima kelas gen MADS-box yang diamati, hanya gen C yang berhasil diamplifikasi. Hasil menunjukkan bahwa gen C terekspresi di semua bagian bunga crested. Berdasarkan hasil tersebut, homeosis pada bunga crested bukan disebabkan karena tidak terekpresikannya gen C. Dibutuhkan penelitian lebih lanjut untuk mengetahui tingkat ekspresi tiap kelas gen MADS-box terhadap variasi bunga crested di alam.

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The aim of this study is to know the variation of Hibiscus rosa-sinensis L. crested flower in nature, and to know its correlation against MADS-box gene expression. The study was conducted through morphological, anatomical, and molecular observation. Morphological sections were carried out on 200 samples of flowers by measuring the length of staminal column, counting the number of perianthium, and observing the external structure of ovaries. Anatomical sections were carried out on 137 samples of flowers by observing the internal structure of ovaries. The results showed that H. rosa-sinensis crested flower has a high variety in the shape of flower. Two main parts of crested flower that effecting its variety in nature are staminodium petaloid and stamen-petal intermediate that lied in the position of stamen and petal. This phenomenon is assumed as homeotic due to the absence of C gene expression that belong to MADS-box gene family. Based on molecular observation, AGAMOUS gene (MADS-box class C) expressed in all of crested flower parts, including staminodium petaloid and stamen-petal intermediate. This results is on contradiction with the assumption that homeosis in H. rosa-sinensis caused by the absence of gene C. Further research is needed to know the expression of others MADS-box class genes expression, including their level of expression in each parts of crested flower.