- THE EMBRYO
• Cotyledons
• Hypocotyl
• Radicle
• Plumule
• Protoderm
• Ground meristem
• Procambium
- From embryo to the adult plant
- After the seed germinates,the apical meristem of the shoot forms,in regular sequence ,leaves,nodes,and internodes.
- Apical meristem in the axils of leaves produce axiliary shoots which in turn,have other axillary shoots.
- As a result of such activity the plant bears a system of branches on the main steam.
4. If the axillary meristem remain in active ,the shoot faits to branch as,for example ,in many palms.
5. The apical meristem of the root located at the tip of hypocotyl or of the radicle,as the case may be forms the taproot(the primary root).
6. In many plants the taproot produces branch roots( secondary root)from new apical meristem originating deep in the taproot(endogenous origin)
7. The branch roots produce further branches in their turn.
8. Thus ,a much branched root system result.
9. In some plants,notably monocotyledons the root system of the adult plant develops from adventitious roots arising on brushlike (fibrous root)because the individual roots are similar to one another in length and form.
10. at appropriate time,determinated in part by an endogenous rhythm of growth and in part by enviromental condition,expecially light and temperature,the vegetative apical meristem of the shoot is changed into a reproductive apical meristem that is,in angiosperms,into a floral apical meristem.
11. The stage of development that ends with the maturation of the more or less direct derivatives of the apical meristems is referred to as primary growth.
a complete plant body with root,stems,leaves,flowers,fruits,and seeds and with its dermal system,and the vascular system is produced by primary growth.
12. Small dicotyledons annual and most of the monocotyledons complete their live cycle by primary growth.
the mayority of dicotyledons and gymnosperms,however,show a secondary stage of growth resulting from the activity of vascular cambium.
13. This meristem increases the amount of vascular tissues and causes thereby the thickening of the axis (stem and root).
The formation of the protective tissue,peridem,which replaces the epidermis ,is also regarded as part of secondary growth.
14. The formation of new cells,tissues,and organs throught the activity of apical meristem involve division of cells.
certain cells of the meristems undergo divisions in such a way that one product of a division becomes a new body cell,the other remains in the meristem.
APICAL MERISTEM AND DERIVATES
1. The cells remaining in the meristem may be called the initials their products by division contributed to the body,the derivates.
The concept of initials and derivates should,however,include the qualification that initials are not inherently different from their derivatives and may become supplaned by their derivatives.
2. The concept of initial and deritivates is taken up from various aspects in connection with the description of the vascular cambium and the apical meristems of root,and shoot.
3. The term apical meristem refers to a complex of cells composed of the initials and their immediate derivatives.
The derivatives usually divide also and produce one or more generations of cells before the cytologic changes,denoting differentiation of spesific types of cells and tissues occurs near the tip of root or shoot.
Growth is not limited to the very tip of root or shoot but extends to levels considerably removed from the region usually called the apical meristem.
DIFFERENTIATION
• The progressive change from the structurally simple meristematic tissue to thecomplex and variable tissues and combinations of tissues in the adult plant body is referre to as differentiation.
• the change from the undifferentiated meristematic state to the differentiated adult state.
• Involves the chemical constitution of cells as well as their morphologic,characteristic:
1. Differentiation may be looked upon as double process.first,of becoming different from the meristematic rocursors ,and second,of becoming different from the neighboring cells or tissues.
SPESIALIZATION
• Change in structure of cell,a tissue,plant organ,or entire plant associated with a restriction of functions,potentialilities,or adaptability to varying conditions.
May result in greates efficiency with regard to certain specific functions .
MORPHOGENESIS
• The development of shape and structure of organs and tissues.
• The term morphogenesis can be used with reference to both the development of the external form and that of the internal organization.
Differentiation and spesialization are elements of morphogenesis
PLANT CELL VS ANIMAL CELL
• Some differences between plant cells and animal cell are :
1. Plant cells have cell walls as their outermost layer .
2. Plant cells have chloroplast that contain chlophyll for pigmentation.
3. Plant cells have larger vacuolas (part of the endomembrane system used for storage )than animal cells.
4. Animal cells contain centriols that play a role in mitosis.
5. Animal cells have flagellum connected to the cell membrane which aids in movement of the cell.
Cell walls,chloroplast,larger vacuolas,centrioles,and flagellum are all part of the uniqueness that distinguish plant cells from animal cells.
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