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.
Cork cambium forms tissues that form the cork. Do you agree with this statement? Explain.
Arrange the following in the sequence you would find them in a plant starting from the periphery—phellem, phellogen, phelloderm.
Arrange the following in the sequence you would find them in a plant starting from the periphery – phellem, phellogen, phelloderm.
Protoxylem is the first formed xylem. If the protoxylem lies next to phloem what kind of arrangement of xylem would you call it?
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.
Below is a list of plant fibres. From which part of the plant these are obtained
a. Coir b. Hemp
c. Cotton d. Jute
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)
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 water for their survival. But when watered excessively, plants die. Discuss.
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?
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?
What part of the plant would show the following?
a. Radial vascular bundle
b. Polyarch xylem
c. Well developed pith
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?
Protoxylem is the first formed xylem. If the protoxylem lies next to phloem what kind of arrangement of xylem would you call it?
What is present on the surface of the leaves which helps the plant prevent loss of water but is absent in roots?
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?
Arrange the following in the sequence you would find them in a plant starting from the periphery – phellem, phellogen, phelloderm.
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.
What are the characteristic differences found in the vascular tissue of gymnosperms and angiosperms?
The lawn grass (Cyandon dactylon) needs to be mowed frequently to prevent its overgrowth. Which tissue is responsible for its rapid growth?
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.
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?
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.
Explain the process of secondary growth in the stems of woody angiosperms with the help of schematic diagrams. What is its significance?
Below is a list of plant fibres. From which part of the plant these are obtained?
(a) Coir
(b) Hemp
(c) Cotton
(d) Jute
The stomatal pore is guarded by two kidney shaped guard cells. Name the epidermal cells surrounding the guard cells. How does a guard cell differ from an epidermal cell? Use a diagram to illustrate your answer.