Anatomy of plants
Short Questions and Answers
One Mark Questions with Answers
1.The region or zone of elongation of the root is found
(a) beyond root hair zone
(b) near the point of emergence of seed
(c) behind the root tip
(d) at the root tip
Answer:(c) behind the root tip
2. Grass stems can elongate after initial growth because
(a) secondary meristem
(b) lateral meristem
(c) intercalary meristem
(d) apical meristem
Answer:(c) intercalary meristem
3. Root meristem is
(a) sub apical
Answer:(a) sub apical
4. Tunica corpus theory is meant for
(a) root apex
(b) root cap
(c) lateral meristem
(d) shoot apex
Answer:(d) shoot apex
5. Tunica corpus theory was put forward by
6. When phloem is completely surrounded by xylem, the vascular bundle is
(a) concentric amphivasal
(b) concentric amphicribal
(c) conjoint collateral
(d) conjoint bicollateral
Answer:(a) concentric amphivasal
7. Seive tubes possess
(a) perforated oblique septa
(b) simple oblique septa
(c) perforated long plates
(d) apical and oblique plates
Answer:(a) perforated oblique septa
8. Cork is commercially got from
(a) Ficus religiosa
(b) Quercus suber
(c) Mangifera indica
(d) Pinus roxburghii
Answer:(b) Quercus suber
9. Casparian strips are characteristic of
(a) pericycle cells
(b) endodermal cells
(c) xylem elements
(d) phloem elements
Answer:(b) endodermal cells
10. Lacuna in the vascular bundle of monocot stem is
(b) lysigenous water cavity
(c) mucilage canal
(d) large sized vessel
Answer:(b) lysigenous water cavity
11. Endodermis of dicot stem is also known as
(a) starch sheath
(b) bundle sheath
Answer: (a) starch sheath
12. Pith is formed from
(c) ground meristem
Answer: (c) ground meristem
Two Marks Questions with Answers
1. Differentiate between dicot and monocot leaf
Answer: In dicot leaf the upper surface is dark green and lower surface is light green whereas in monocots the two surfaces are equally green. The epidermal cells have sinuous lateral walls in docot leaf while in monocot leaf the epidermal cells have almost straight lateral walls. Silica is not normally deposited on the epidermal cells in dicot leaf while in monocot leaf silica deposition occurs on the walls.
2. Differentiate between phellem and phelloderm
Answer: Phellem or cork is a tissue formed on outer side of phellogen or cork cambium while phelloderm or secondary cortex is produced on the inner side of phellogen. Phellem is composed of dead cells while phellogen is made of living cells. Phellem is protective in function while phellogen cells take part in storage of food.
3. What are lenticels?
Answer: Lenticels are aerating pores in the bark of plants. They appear on the surface of the bark as raised scars containing oval, rounded or oblong depressions. They occur in woody trees but not in climbers. Normally they are formed in areas with underlying rays for facilitating gas exchange. The lenticels is filled up by loosely arranged thin walled rounded and suberised or unsuberised cells called complementary cells. They enclose intercellular spaces for gaseous exchange.
4. Differentiate between vessels and tracheids.
Answer: A vessel is made of a number of cells while a tracheid is formed from a single cell. The ends are rounded or transverse in vessels while the ends are generally oblique and tapering in tracheids. A vessel is several centimetres in length while a tracheid is only a fraction of a centimetre in length. Vessels are comparatively wider while tracheids are comparatively narrower. The wall is less thickened in case of vessel while the wall is more thickened in tracheid. The lumen is wide in case of vessel whereas the lumen is comparatively narrow in tracheids.
5. Differentiate between xylem and phloem.
Answer: Xylem conducts water or sap while phloem conducts organic food. Xylem also provides mechanical strength while phloem has no mechanical function. Xylem is usually found deep in the plant while phloem is usually situated towards the outer side of the plant. In older plants, xylem often constitutes bulk of the plant body while phloem always forms a small part of the plant body. xylem is made up of three types of dead cells; vessels, tracheids, xylem fibres while phloem contains only one type of dead cells, phloem fibres.
Three Marks Questions with Answers
1. What are collateral bundles?
Answer: Collateral bundles are those conjoint bundles in which phloem and xylem lie together on the same radius with phloem on the outer side and xylem towards the inner side. In gymnosperms and dicot stem strip of vascular cambium occurs between phloem and xylem of each vascular bundle. It is called intrafascicular cambium. The strip of vascular cambium later produces secondary tissues. Such vascular bundles are described as open because the original or primary phloem and xylem separate on the production of secondary tissues by vascular cambium. In monocot stem vascular bundles do not have a strip of vascular cambium they are termed as closed.
2. Differentiate between open vascular bundle and closed vascular bundle.
Answer: In open vascular bundle the vascular bundle contains strip of cambium in between phloem and xylem while in case of closed vascular bundle intrafascicular cambium is absent. In open vascular bundle phloem and xylem do not lie in direct contact with each other while in closed vascular bundle phloem and xylem occur in direct contact with each other. In open vascular bundle due to activity of cambium original or primary phloem and xylem move away from each other, secondary phloem and secondary xylem are formed in between. There is no such activity in closed vascular bundle. Open vascular bundles occur in dicot and gymnosperm stems while closed vascular bundles are found in leaves and monocot stem. Open vascular bundles can be collateral and bicollateral while closed vascular bundles can be collateral or concentric.
3. What are sieve tubes?
Answer: Sieve tubes are elongated tubular conducting channels of phloem. Each sieve tube is formed of several cells called sieve tube members, sieve tube cells or sieve elements. Sieve tube members are placed end to end. The end walls are generally bulged out. They may be transverse or oblique. They have many small pores or sieve pits. Each sieve pore is lined by a layer of callose. Excessive growth of callus however closes the sieve pore. Due to the presence of sieve pits the end walls are commonly called sieve plates. In some cases the ends walls of sieve elements possess more than one porous area. Such an end wall is called compound sieve plate, example grapevine. The sieve plates connect the protoplasts of adjacent sieve tube members.
In non flowering plants sieve cells remain separate. They are narrower but more elongated as compared to individual sieve tube members. Sieve tube takes part in conduction of organic food.
4. What are companion cells?
Answer: Companion cells are narrow elongated and thin walled living cells. They lie on the sides of the sieve tubes and are closely associated with them through compound plasmodesmata. They are rectangular in a transverse section. The cells have dense cytoplasm and a prominent nucleus. It is supposed that the nuclei of the companion cells control the activities of the sieve tubes through plasmodesmata. Companion cells also help in maintaining a proper pressure gradient in the sieve tube elements. Sieve tube member and its adjacent companion cells are derived from the same mother cell. Death of one results in death of the other as well. Companion cells are replaced by modified parenchyma cells (albuminous cells) in non flowering plants.