PLANT ANATOMY & PLANT TISSUE
The plant body is made up of cells.cells are organized to form tissues, tissue system and organs in a sequential organization.
Study of the internal strctural organization of plant organs is known as plant anatomy.
Two groups of the angiosperms i.e.Dicot and monocot show different anatomical composition.
Tissue : Tissue is a group of cells having a comman origin, which are grouped together to perform specific functions.
Plant tissues are of two types: (1) Meristematic and (2) Permanent
– meristematic tissues consists of actively dividing cells.
– Based on their location, they are of 3 types:
1) Apical meristem
2) Intercalary meristem
3) Lateral meristem
– Apical meristem and Intercalary meristems,as they appear early in the life of plant and contribute to the formation of primary plant body, they are considered primary meristem.
– Secondary meristematic tissue : the meristems that occurs in the mature regions of shoots and roots of many plants and apper later than primary meristem is called secondary or lateral meristem.
– Cells of permanent do not possess the property of cell division and these tissues are structurallyand functionally specialized.
– permanent tissues are of two types:
(a) simple and (b) complex (conductive)
– simple permanent tissues consists of similar types of cells.
– They are divided into 3 types.
(a) parenchyma (b) collenchyma (c) sclerenchyma
– While complex tissues is a group of more than one type of cells, working together as a unit to perform definite functions.
– they are of two types:
(a) Xylem and (b) Phloem
– Xylem is concerned with transportation of water and minerals.
– Phloem transports nutritive substance.
Anatomy of plant organs :–
Three types of tissues systems are found in plant organs like root, stem and leaf.
(a) Epidermal tissue system
(b) Ground tissue system
(c) Vascular tissue system
– In most of the dicatyledons,after completion of the primary growth, further increase in girth(diameter)takes place due to formation of secondary tissues.The length wise growth of organs is due to apical meristem.
– the secondary growth involves lateral meristems like vascular cambiun work cambium.
A+R type questions mark the coorect choice as:
(A) If both A and R are true and R is the correct explanation of A
(B) If both A and R are true but R is not the corrcet explanation of A
(C) If A is correct but R is false
(D) If both A and R is false
(1) A : In woody stems the amount of heart wood continues to increase year after year
R: The activity of the camibcal ring continues uninterrupted – (1999,2007)
(2) A: thick cuticle is mostly present in disease resistant plants
R: Disease causing agents can not grow on cuticle and cannot invade the cuticle (1997)
(3) A: Rhizobial aggregates have been observed at distinct sites on curled root hairs.
R: The infection thread is formed by a process of invagination of the hair cell walls in the region
of curling. (1999)
(4) A: Vascular cambin is considered as lateral meristem.
R: It give rise to lateral shoots (2000)
(5) A: Monocot stem consists of colateral open vascular bundles.
R: If camblum is present such vascular bundles are called closed type (2001)
(6) A: The collenchyma is thick walled living tissue.
R:The collenchyma is thickened due to the deposition of pectin.