Malvaceae

According to Berry (2015), the family Malvaceae, where genus Hibiscus belongs, consists of 243 genera and at least 4225 species of herbs, shrubs, and trees. Some of the distinct features of the species which belongs to Malvaceae includes stamens with fused filaments forming a tube, numerous anthers spreading from the filament tube, and long style emerging above stamens and branched (usually) at the tip (Malvaceae, 2004). Other economically important members of the family are cotton (various Gossypium species), cacao (Theobroma cacao), durian (Durio species), and okra (Abelmoschus esculentus). Morphology Root System. Roselle is an erect plant that grows to about 3.5 m tall and is typically dark green to red in colour with a deep penetrating

The flowers are complete having both the pistil and stamen. It is axillary and varies in colour. It grows up to 5 in (12.5 cm) wide with a rose or maroon eye (Morton, 1987). The petals usually last for only a day (Cooper, 1993). Haarer (1952) described the calyx as cup-shaped, longer than the epicalyx, and often purplish in colour. The segments were deltoid, acuminate, and studded with asperites (Haarer, 1952). Types. There are two important types of roselle namely Hibiscus sabdariffa var. sabdariffa and Hibiscus sabdariffa var. altissima. Hibiscus sabdariffa var. sabdariffa. This type of roselle is cultivated mainly for its edible calyces. The plant is shorter and has more branches compared to var. altissima. Though the stalk could also be used in producing fibre, the quality it produced is inferior in quality compared to those of var. altissima. Hibiscus sabdariffa var. altissima. This type of roselle is cultivated mainly for its fibre. This type produces inedible calyces. It is an erect plant and sparsely-branced. The fiber that it produced is a good substitute for jute.

Flowering of

Roselle is a short-day and photoperiodic plant and would not flower when exposed to 13.5 hours of daylight but would start to flower at 11 hours (Duke, 1982). According to Mansour (1975), roselle would still be in the vegetative stage at a 16 hour day. Roselle that were grown with changing daylengths developed more branches compared to those that were grown in continuous short days or long days (Mansour, 1975). The leaf blades of the plants are the one responsible for detecting the photoperiods (Hillman, 1962). The movements and the position of the leaves also affect the flowering because it affects the amount of light that would reach the leaf surface resulting in a slight change in the time of flowering (Vince-Prue, 1975). According to Vince-Prue (1975), the presence of clouds during twilight and dawn has an effect on flowering making it a little earlier or end a little bit later than the usual. One way of controlling daylength to achieve the longer night is by putting a black cloth over plants in the late afternoon or evening and removing it in the morning (Currey et al., 2017). It is important that there will be no light interruption to initiate flowering (Dictionary of Botany, 2003). The plants are able to measure the length of darkness through the use of phytochrome which has two forms: phytochrome far-red (Pfr)