Principals of Flowering Plants Taxonomy BOT 222 Dr. Najat Abdulwahab Bukhari Lecture7

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Botany department Vision and Mission Vision: upgrading the academic and research to keep pace with scientific progress and requirements of society. Mission: Development of Academic process and develop scientific research through strategic planning and a clear vision for science and technology at the country level. As well as training of national cadres, and the introduction of a methodology developed to meet the different needs of society, and to serve the various research and developmental projects in the community

Course Description Topics to be Covered Topic No of Weeks Contact hours - Historical review of plant taxonomy (industrial , natural, evolution) 1 2 - Nomenclature - Classic taxonomy (morphological taxonomy of vegetation and floral characters – Fruits and seed characters. 5 - Key to taxonomical unites. - Fertilization and seed formation - The different kinds of fruits - The sexual differentiations of flowers and their fertilization 14

Placenta in flower is where the ovules is attached to the ovary. The ovules are attached to the placental wall of the ovary through a structure known as the funiculus

Ovules

Ovules in flowering plants arise often on a swollen in the carpel wall, which is called placenta. The placenta appear first as a small lump consists of tissue cells and sub tissue, then goes through the vascular bundles. Then, Sub tissue cells divides and develops to generate the funiculus. At the apic of the funiculus grows the ovules body.

The Ovule and the placenta are connected via the funiculus. The body of the ovule fuses with the funicle to form the hilum in the seed. The ovule consists of one or two integuments, accordingly the ovules are called unitegmic or bitegmic respectively. The integuments leave a small opening on one side called the micropyle.

The end of the ovule having the micropyle is called the micropylar end. The opposite end is called the chalazal end. The integuments enclose a tissue called the nucellus. Nucellus in turn encloses the embryosac, the female gametophyte.

Ovule parts and development The ovule is composed of diploid maternal tissue that gives rise to the haploid tissue of the female gametophyte. The maternal tissues of the ovule include the integuments and the nucellus. The next "generation" formed within the ovule are the haploid megaspore and megagametophyte, or embryo sac

After fertilization of the egg cell and formation of a zygote, the ovule contains the embryo of the next sporophyte generation and, in flowering plants, the triploid endosperm.

Mature ovule in longitudinal section

Nucellus, megaspore and perisperm The nucellus (plural: nucelli) is the central portion of the ovule inside the integuments. It consists of diploid maternal tissue and has the function of a megasporangium. In immature ovules, it contains a megasporocyte (megaspore mother cell), which undergoes sporogenesis via meiosis

Ovule various types: Ortho tropous: growing straight during development so that the nucellus axis, funlculus and micropyle are on one straight line. The micropyle is at the apex.

Hemi tropous: the nucellus axis and micropyle are Orthogonal with the funlculus .

Ana tropous: the nucellus axis is straight with funlculus but bended to 180 ° , so the micropyle is facing downward and situated near the base and in paralle with the funlculus as in (Zygophyllum)

Camphylo tropous: the Ovule looks like kidney, Partially inverted and curved such that the micropyle nearly meets the funiculus.

Three common types of ovule axes in longitudinal section

Straight ovule structure

placentation Placentation is the arrangement of ovules and placenta within the ovary. This varies from flower to flower.

Placentation types Marginal In this type, the ovary is, monolocular and the placenta is on the ventral suture. The ovules are attached to the placenta which is on the margin.

Parietal In this type, the ovary has two or more carpels, and is syncarpous, and monolocular. Here there are as many placentae as the number of carpels and the ovules are attached to those placentae at the periphery. e.g., Cucurbita, Argemone

Central In this type the ovary is monolocular, wherein the ovules are borne on a central axis that reaches the top of the ovary. e.g., Primula, Sandal Wood.

Free central In this type the ovary is monolocular, wherein the ovules are borne on a central axis that reaches the top

Basal In this type, the ovary is monolocular. The ovules are few or reduced to one and borne at the base of the ovary. The ovule when solitary often fills the ovary cavity. e.g., Sunflower.

Apical The ovary is monolocular. The one or two ovules are borne at the roof of the ovary. e.g., Morus