Deciduous plants shed their leaves during hot summer or in autumn. This process of shedding of leaves is called abscission. Apart from physiological changes what anatomical mechanism is involved in the abscission of leaves.
Separation of leaves, bracts, flowers, floral parts and fruits from the plant without causing any injury is called abscission. Abscission layer is made up of two layers of cambium like cells. Cells of these layers are smaller and contain more of protoplasm and starch. Tyloses develop in the xylem of vascular tissue. In cambium like cells of abscission layer, the middle lamella swells up anpl becomes mucilaginous. Later on in response to any of several environmental changes (such as lowering temperatures, decreasing day lengths or light intensities, lack of adequate water and poor availability of nutrients from the soil, etc.) the pectins in the middle lamella of the cells of abscission are broken down by enzymes due to which the cell separate apart. The leaf is now attached to the stem only with the help of vascular tissue, which separates from the stem by wind and rain and leaf falls down from the plant.
Trunks of some of the aged tree species appear to be composed of several fused trunks. Is it a physiological or anatomical abnormality? Explain in detail.
Arrange the following in the sequence you would find them in a plant starting from the periphery—phellem, phellogen, phelloderm.
Cork cambium forms tissues that form the cork. Do you agree with this statement? Explain.
The lawn grass (Cyandon dactylon) needs to be mowed frequently to prevent its overgrowth. Which tissue is responsible for its rapid growth?
Arrange the following in the sequence you would find them in a plant starting from the periphery – phellem, phellogen, phelloderm.
Match the following and choose the correct option from below.
| A. | Meristem | (i) | Photosynthesis, storage |
| B. | Parenchyma | (ii) | Mechanical support |
| C. | Collenchyma | (iii) | Actively dividing cells |
| D. | Sclerenchyma | (iv) | Stomata |
| E. | Epidermal tissue | (v) | Sclereids |
Options:
(a) A—(i), B—(iii), C—(v), D—(ii), E—(iv)
(b) A—(iii), B—(i), C—(ii), D—(v), E—(iv)
(c) A—(ii), B—(iv), C—(v), D—(i), E—(iii)
(d) A—(v), B—(iv), C—(iii), D—(ii), E—(i)
Trunks of some of the aged tree species appear to be composed of several fused trunks. Is it a physiological or anatomical abnormality? Explain in detail.
Protoxylem is the first formed xylem. If the protoxylem lies next to phloem what kind of arrangement of xylem would you call it?
While eating peach or pear it is usually seen that some stone like structures get entangled in the teeth, what are these stone like structures called?
Plants require water for their survival. But when watered excessively, plants die. Discuss.
What is present on the surface of the leaves which helps the plant prevent loss of water but is absent in roots?
The transverse section of a plant material shows the following anatomical features – (a) the vascular bundles are conjoint, scattered and surrounded by a sclerenchymatous bundle sheath, (b) phloem parenchyma is absent. What will you identify it as?
Each of the following terms has some anatomical significance. What do these terms mean? Explain with the help of line diagrams.
a. Plasmadesmoses/Plasmodesmata
b. Middle lamella
c. Secondary wall
The cross-section of a plant material showed the following features when viewed under the microscope.
(a) The vascular bundles were radially arranged.
(b) Four xylem strands with exarch condition of protoxylem.
To which organ should it be assigned?
Plants require waterfortheir survival. But when watered excessively, plants die. Discuss.
The cross-section of a plant material showed the following features when viewed under the microscope.
a. The vascular bundles were radially arranged.
b. Four xylem strands with exarch condition of protoxylem.
To which organ should it be assigned?
What part of the plant would show the following?
a. Radial vascular bundle
b. Polyarch xylem
c. Well developed pith
Below is a list of plant fibres. From which part of the plant these are obtained?
(a) Coir
(b) Hemp
(c) Cotton
(d) Jute
Epidermal cells are often modified to perform specialised functions in plants. Name some of them and function they perform.
While eating peach or pear it is usually seen that some stone like structures get entangled in the teeth, what are these stone like structures called?
Cut a transverse section of young stem of a plant from your school garden and observe it under the microscope. How would you ascertain whether it is a monocot stem or a dicot stem ? Give reasons.
Assume that a pencil box held in your hand, represents a plant cell. In how many possible planes can it be cut? Indicate these cuts with the help of line drawings.
Product of photosynthesis is transported from the leaves to various parts of the plants and stored in some cell before being utilised. What are the cells/ tissues that store them?
The lawn grass (Cynodon dactylon) needs to be mowed frequently to prevent its overgrowth. Which tissue is responsible for its rapid growth?
Explain the process of secondary growth in the stems of woody angiosperms with the help of schematic diagrams. What is its significance?
Distinguish between the following:
(a) Exarch and endarch condition of protoxylem
(b) Stele and vascular bundle
(c) Protoxylem and metaxylem
(d) Interfasicular cambium and intrafasicular cambium
(e) Open and closed vascular bundles
(f) Stem hair and root hair. .
The transverse section of a plant material shows the following anatomical features – (a) the vascular bundles are conjoint, scattered and surrounded by a sclerenchymatous bundle sheath, (b) phloem parenchyma is absent. What will you identify it as?
Match the following and choose the correct option from below.
| A. | Cuticle | (i) | Guard cells |
| B. | Bulliform cells | (ii) | Single layer |
| C. | Stomata | (iii) | Waxy layer |
| D. | Epidermis | (iv) | Empty colourless cell |
Options:
(a) A—(iii), B—(iv), C—(i), D—(ii)
(b) A—(i), B—(ii), C—(iii), D—(iv)
(c) A—(iii), B—(ii), C—(iv), D—(i)
(d) A—(iii), B—(ii), C—(i), D—(iv)
Trunks of some of the aged tree species appear to be composed of several fused trunks. Is it a physiological or anatomical abnormality? Explain in detail.