Dr. Najat Abdulwahab Bukhari Lecture 5

University Vision and Mission  Vision: To be a world-class university and a leader in developing Saudi Arabia’s knowledge economy  Mission: To provide students with a quality education, conduct valuable research, serve the national and international societies and contribute to Saudi Arabia’s knowledge economy through learning, creativity, the use of current and developing technologies and effective international partnership.

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 Botany department Vision and Mission

Course Description Topics to be Covered TopicNo of Weeks Contact hours - Historical review of plant taxonomy (industrial, natural, evolution) 12 - Nomenclature12 - Classic taxonomy (morphological taxonomy of vegetation and floral characters – Fruits and seed characters Key to taxonomical unites.12 - Fertilization and seed formation22 - The different kinds of fruits22 - The sexual differentiations of flowers and their fertilization 22 14

connective The part of the stamen joining the anther cells: Types of connective: 1.Attached by the back, Dorsifixed, as in Mangnolia.

2.attached at the base, (Basifixed),as in most of the floral plants (Ranunculaceae )

3.Medifixed, as in Graminacea family, most of this family is wind pollination

4.Andenate :fusion or united stamens,

Plant classification scientists rated flowers with few stamens number (five or more) more revolutionary than flowers with large number of stamens. When anthers are few in number it gives stronger pollen grains and more resistant to the external conditions. While more stamens number weaken gives less strength and resistant pollen grains and less energy in the pollination process.

Anther Anther is a bi-lobed structure consists of two lobes linked by Connective. Each lobe has cavity (pollen chambers or sacs ) winch carries large number of pollen grains. Anthers are rarely consists of one lobe, as in the Cucurbitaceae Malvavceae family. Anther may not contain pollen grains, as in some Senna stamens (Cassia Angustifolia)

Each spore sac is covered from the outside with: 1. A tissue layer ( protective). 2.Inside of this layer fiber cells “Fibrous layer”. The fibrous layer consists of helps in dehiscence. 3.After the fibrous layer comes few intermediate layers (storage). These tree layer are the (outer exine) 4. then the Tapetum tissue (Nutritive layer) as it cells produce food for the grains, surrounding the pollen grains cavity. (inner intine) Anther structure

a typical angiosperm anther is tetra- sporangiate. It consists of an anther wall and microspore mother cells. These microspore pollen mother cells are diploid and undergo meiosis. Each microspore mother cell divides meiotically to form four haploid microspores. Therefore, each cell divides into four pollen grains.

 Pollen grain and sperm cell differentiation.  Anther enlargement  Tissue degeneration  Dehiscence and pollen release. Anther development

opening up of anthers differ according to the plants and the environment in which they live : 1.Longitudinal, as in most of plants Anther development

2.Trans verse, as in Hibisus.

3.Byapicalpores, as in Ericaceae.

4.Bhvalves, as in Lauraceae.

Anther development mechanism:  Attributable anther development to the Fibrous layer, where it is not even in thickness. When its dry, the outer tissue becomes dry too and loses water, then cells shrink as a result of water lost, this causes to open along the lateral line that separates the pollen sacs in each lob.

In every lobe there is linear line, which is the opening line and is called the ventral surface. The other side represents the dorsal surface. If the ventral surface is heading towards the pistil, then the anthers are called “Entrose”. If the line is towards the calyx then the anthers is called “Extrose”

Some anthers may head towards the pistil while others towards the corolla in the same flower. “internal and external openness at the same time.” The number of stamens varies from one plant to another as some flowers, plants contain: 1 - just two stamens as in the olive 2 - only one stamen, as in the plant Alsntrutc