Tuesday, 2 September 2014

TEXTBOOK ANSWERS AND ANALYSIS Anatomy of Plants CBSE CLASS-XI-BIOLOGY




1) State the location & functions of different types of meristems.

 On Basis of location it is of 3 types

a) Apical – Present at the apices of stem, root & their branches & functions as growth in length, formation of primary tissues.

b) Intercalary – It is found below or above the stem nodes & leaf bases & functions as growth of internodes leaves & correction of position in lodged stems.

c) Lateral – a) cork cambium – develops from hypoderms in stems & pericycle of root and functions as protective cork.

b) Vascular Cambium – In stem from Interfasicular cambium strips & inherfasicu8llar strips. In root from conjuctive parin tyma & pricycle.

Functions :- Formation of secondary phloem on outside & secondary xylem on innerside.


2) Cork cambium forms tissues that form the cork. Do you agree with this statement?


Yes I do.

  Cork cambium is a secondary meristem developing from pericyell of root showing bi-polar divisions on outer & inner side tissue formed on outer lalyer is parn chymatons & soon the wall become subcrised & protoplasm dies. The dead cue filled with tonnim alkalids & air is called cork or phellen.


3) Explain the process of secondary growth in stem of wood angiosperms with the help of schematic diagram. What is its significance?

Secondary growth in stem is because of two types of cambium
  

1. vascular combium
      
2.   Cork cambium.





                    Fig: A complete ring of vascular cambium formed by strips of intrafascicular cambium Inter – fascicular cambium.



Vascular cambium :- Secondary growth begins with the initiation of the vascular cambium, a cylinder of meris thematic tissue thatg produces additional xylic & phloic tissues. The cells that eventually form the vascular cambium come from two sources, thge procambvium in the vascular bundles & the interfascicular parnchyna cells. Between vascular bondler . the vascular cambium is formed when the cells of interfascicular parenchyma de-differentiate and divide perictinally, in a plane parallu to the surface of the stem. The cells in the procambium divide in a similar fashion.

Cork Cambium – Produces secondary growtn tissues called peridern. Cork cambium developer secondarily from a suepidermal layer of liwing alls & produces cork on the outside & phellodern on inner side.

Significance – It resums in the thickening of a stem, stalk or root, produced by cell division in vascular cambium.

4. Draw illustrations to bring out anatomical difference between

a) Monocot root & dicot root

b) Ronocot stem & dicot stem
                         


Diagram given in ncert book.

Ans – a) i) Cortex in monocot roots are wider
     ii)In monocot roots larger no of vascular bundles are present.
     iii) Pith is present in monocot roots.
     iv) In monocot root there is rounded vascular boundless & polygonal in dicot root.

Anms – b) i) In dicot stem hair is presence & absence in monocot stem.
          ii) In dicot stem collenchymatous hypodcermis is present & sclenenchymatous hypodermis is present in mono cot stem.
          iii) Vascular bundlesw are open in monocot & closed in dicot.


5,   Cut a transuerse section of young stem of a plant from your school garden & obscruit under the microscope. How would you ascertain wheather it is monocot stem or dicot stem give reason.

     If the section is of dicot stem if it has concentric arrangement of ground tissues, open vascular bundles arranged in polygon vessels.

     If the section is of mono cot stem the ground tissues are undifferentiated, vascellar bundles are closed.

6. Why are xylem & phloem called comples tionves?

     A complex tissue is one which contains more than two types of cells which perform common function.

     As xylem is formed of 4 types of cells –
     Tracheids, vessels, xylem parenchymja & xylem fibres which all help in conduction of sap.

     Phloem is formed by 4 types of cells – sieve companion cells, phloem parenchyma & phloem fibres . they help in conduction of food – to directional

7.   What is stomatal apparatus ? Explain the structure of stomata with labelled diagram.

     A pair of guard cells with or without surrounding subsidiary cells that functions as a value to open or close a stomatal pore forf gaseous exchange & transpirations is called stomatal appa – ratun.

     The guard cells contains choloropp[last & small voceloles which are thick – walled in the area opf contact & thin walked else where. When the guard cells swellep due to on do osmosis the thin – walled sides expand. The thick walls of the two guarfd cells swell up[ due to endo-osmosis & the thin wall side expands.

8.   Name the three baris tissue systems in the following flantgs. Give the tissue name under each system.

3 tissues


     1.Epidermal tissue system
    
     2. Ground tissue System


         
      3.Vascular tissue system
                         
Epidermal tissue system – Epidermis & epidermal appendages. It consist of epidermal & guard cells. It includes root tairs, stem hairs etc.

Ground tissue system – Hypodermis, corten endodermis, pericycle, pith & medullary rays.

Vascular tissue system – Vascular bundles, phloem, xylem & vascularf cambium.


10. What is periderm? How periderm formation does takes place in dicot stem?

                  It is formed towards the surface of stems & roots having phellem, phellogm & phelloderm.

Phellogen or cork cambium – It develops in a subepiderminal layer in stem & from pericycle in roots & undergoes bipolar divisions. The all of the outer side undergoes deposition of tannins & death of cellular contents. The outer tissue of dead subsidiary cell is called phellem. 
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Written By Badal Paul
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