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#	Question	Answer
1	What are the two processes that together make up development in plants?	Growth and differentiation.
2	What is the first step in plant growth?	Seed germination.
3	Under what condition do seeds germinate?	Seeds germinate when favourable environmental conditions exist.
4	What happens to seeds in the absence of favourable conditions?	They enter a period of suspended growth or rest.
5	What resumes when favourable conditions return after seed dormancy?	Metabolic activities and growth resume.
6	Which factors govern and control plant developmental processes?	Intrinsic (internal) and extrinsic (external) factors.
7	How is growth defined in plants?	An irreversible permanent increase in size of an organ, its parts, or an individual cell.
8	Growth is generally accompanied by which metabolic processes?	Both anabolic and catabolic processes.
9	Why is plant growth considered indeterminate?	Because plants retain the capacity for unlimited growth throughout life.
10	Which structures are responsible for unlimited growth in plants?	Meristems.
11	What is the characteristic feature of meristematic cells?	They can divide and self-perpetuate.
12	What is meant by the open form of growth?	Continuous addition of new cells to the plant body by meristem activity.
13	Which meristems are responsible for primary growth in plants?	Root apical meristem and shoot apical meristem.
14	What is the role of lateral meristems in dicots and gymnosperms?	They increase the girth of plant organs.
15	What is secondary growth?	Increase in the girth of plant organs due to lateral meristems.
16	Name two lateral meristems.	Vascular cambium and cork cambium.
17	Growth at the cellular level mainly results from an increase in what?	Protoplasm.
18	List some parameters used to measure growth in plants.	Fresh weight, dry weight, length, area, volume, and cell number.
19	Into how many phases is the period of growth divided?	Three phases.
20	Name the three phases of growth.	Meristematic phase, elongation phase, and maturation phase.
21	Which cells represent the meristematic phase of growth?	Constantly dividing cells at root and shoot apices.
22	Mention two characteristics of meristematic cells.	Rich in protoplasm and possess large conspicuous nuclei.
23	What type of cell walls do meristematic cells possess?	Thin, primary, cellulosic cell walls.
24	What are the characteristics of cells in the elongation phase?	Increased vacuolation, cell enlargement, and new cell wall deposition.
25	What happens during the maturation phase of growth?	Cells attain maximal size with wall thickening and protoplasmic modifications.
26	Which meristems are mainly responsible for primary growth in plants?	Root apical meristem and shoot apical meristem.
27	What is the main function of primary growth?	Elongation of plants along their axis.
28	Which meristems are responsible for secondary growth in plants?	Vascular cambium and cork cambium.
29	What is secondary growth?	Increase in the girth of plant organs due to lateral meristems.
30	Growth at the cellular level mainly results from an increase in what?	Increase in the amount of protoplasm.
31	Why is protoplasm increase difficult to measure directly?	Because it cannot be measured directly, proportional quantities are measured instead.
32	Name some parameters used to measure plant growth.	Fresh weight, dry weight, length, area, volume, and cell number.
33	How many new cells can a single maize root apical meristem produce per hour?	More than 17,500 new cells per hour.
34	By how much can watermelon cells increase in size?	Up to 3,50,000 times.
35	Growth in maize root apical meristem is expressed as an increase in what?	Increase in cell number.
36	Growth in watermelon cells is expressed as an increase in what?	Increase in cell size.
37	How is the growth of a pollen tube measured?	In terms of length.
38	Which parameter denotes growth in a dorsiventral leaf?	Increase in surface area.
39	Name the three phases of growth.	Meristematic phase, elongation phase, and maturation phase.
40	Which cells represent the meristematic phase of growth?	Constantly dividing cells at root and shoot apex.
41	Mention two characteristics of meristematic cells.	They are rich in protoplasm and possess large conspicuous nuclei.
42	What type of cell walls are found in meristematic cells?	Thin, primary, cellulosic cell walls with abundant plasmodesmatal connections.
43	Which phase occurs just behind the meristematic zone?	Phase of elongation.
44	What are the characteristics of cells in the elongation phase?	Increased vacuolation, cell enlargement, and new cell wall deposition.
45	Which phase lies beyond the elongation phase?	Phase of maturation.
46	What happens to cells during the maturation phase?	They attain maximal size with wall thickening and protoplasmic modifications.
47	What is growth rate?	Increased growth per unit time.
48	How can the rate of growth be expressed?	Mathematically.
49	What are the two major patterns of growth rate increase?	Arithmetic growth and geometrical growth.
50	In arithmetic growth, after mitotic division, how many daughter cells continue to divide?	Only one daughter cell continues to divide while the other differentiates and matures.
51	The growth rate in plants may be of which two types?	Arithmetic growth and geometrical growth.
52	What happens in arithmetic growth after mitotic cell division?	One daughter cell continues to divide while the other differentiates and matures.
53	Which example best explains arithmetic growth?	Root elongating at a constant rate.
54	What type of curve is obtained in arithmetic growth when organ length is plotted against time?	A linear curve.
55	Write the formula for arithmetic growth.	L_t = L_0 + rt
56	In the arithmetic growth equation, what does (L_0) represent?	Length at time zero.
57	In the arithmetic growth equation, what does (r) represent?	Growth rate or elongation per unit time.
58	What characterises the initial phase of geometrical growth?	Initial growth is slow and is called the lag phase.
59	During which phase does geometrical growth increase rapidly?	Log phase or exponential phase.
60	What happens to progeny cells in geometrical growth?	Both progeny cells retain the ability to divide and continue dividing.
61	Why does growth slow down in geometrical growth?	Due to limited nutrient supply leading to a stationary phase.
62	Which curve is obtained when growth parameter is plotted against time in geometrical growth?	Sigmoid or S-curve.
63	Sigmoid growth curve is characteristic of what?	Living organisms growing in a natural environment.
64	In the exponential growth equation, what does (W_1) represent?	Final size (weight, height, number, etc.).
65	In the exponential growth equation, what does (W_0) represent?	Initial size at the beginning of the period.
66	What does (e) represent in the exponential growth formula?	Base of natural logarithms.
67	What is relative growth rate?	Measure of the ability of the plant to produce new plant material.
68	What is another name for relative growth rate?	Efficiency index.
69	What is absolute growth rate?	Total growth per unit time.
70	What is relative growth rate in quantitative comparisons?	Growth per unit time expressed on a common basis, such as per unit initial parameter.
71	Name three essential elements required for plant growth.	Water, oxygen, and nutrients.
72	Why is water essential for plant growth?	It is required for cell enlargement and provides medium for enzymatic activities.
73	How does oxygen help in plant growth?	It releases metabolic energy essential for growth activities.
74	Why are nutrients required by plants?	For synthesis of protoplasm and as a source of energy.
75	How does temperature affect plant growth?	Every plant has an optimum temperature range best suited for growth.
76	Which environmental signals affect certain phases of plant growth?	Light and gravity.
77	What is differentiation in plants?	The process by which cells mature to perform specific functions.
78	Which cells differentiate and mature to perform specific functions?	Cells derived from root apical meristems, shoot apical meristems, and cambium.
79	What changes occur in cells during differentiation?	Structural changes occur in cell walls and protoplasm.
80	What happens to cells while forming tracheary elements?	They lose their protoplasm.
81	What type of secondary cell wall is present in tracheary elements?	Strong, elastic, lignocellulosic secondary cell wall.
82	Why do tracheary elements develop strong lignocellulosic walls?	To carry water to long distances under extreme tension.
83	What is dedifferentiation?	The process by which living differentiated cells regain the capacity to divide.
84	Give examples of dedifferentiation in plants.	Formation of interfascicular cambium and cork cambium from differentiated parenchyma cells.
85	What is redifferentiation?	The process in which cells formed after dedifferentiation mature again to perform specific functions.
86	Why is differentiation in plants considered open?	Because cells arising from the same meristem can have different structures at maturity.
87	What determines the final structure of a cell or tissue at maturity?	Its location within the plant body.
88	Cells positioned away from root apical meristem differentiate into what?	Root-cap cells.
89	Cells pushed towards the periphery mature into what?	Epidermis.
90	What is development in plants?	All changes an organism undergoes during its life cycle from germination to senescence.
91	What is plasticity in plants?	The ability of plants to follow different developmental pathways in response to environment or life phases.
92	What is heterophylly?	Occurrence of leaves of different shapes in the same plant.
93	Name plants showing heterophylly.	Cotton, coriander, larkspur, and buttercup.
94	How are juvenile and mature leaves different in heterophyllous plants?	Juvenile leaves differ in shape from mature leaves.
95	In buttercup, why are leaf shapes different in air and water?	Due to environmental influence causing heterophyllous development.
96	Heterophylly is an example of what phenomenon?	Plasticity.
97	Which stages are shown in the developmental sequence of a plant cell?	Cell division, plasmatic growth, differentiation, expansion, maturation, senescence, and death.
98	Which type of cell begins the developmental sequence in plants?	Meristematic cell.
99	Which stage follows expansion (elongation) in plant cell development?	Maturation.
100	Which stage ultimately follows maturation in plant development?	Senescence and death.
101	Development in plants is broadly considered as the sum of what two processes?	Growth and differentiation.
102	Which factors control development in plants?	Intrinsic and extrinsic factors.
103	What are intracellular intrinsic factors in plant development?	Genetic factors.
104	What are intercellular intrinsic factors in plants?	Chemicals such as plant growth regulators (PGRs).
105	Name some extrinsic factors affecting plant development.	Light, temperature, water, oxygen, and nutrition.
106	What are plant growth regulators (PGRs)?	Small, simple molecules of diverse chemical composition.
107	Give examples of indole compounds among PGRs.	Indole-3-acetic acid (IAA).
108	Which PGR is an adenine derivative?	Kinetin (N6-furfurylamino purine).
109	Which PGR is derived from carotenoids?	Abscisic acid (ABA).
110	Gibberellic acid (GA3) belongs to which chemical class?	Terpenes.
111	Which gaseous plant growth regulator is mentioned in the text?	Ethylene (C2H4).
112	What are other names for plant growth regulators?	Plant growth substances, plant hormones, or phytohormones.
113	Into how many groups are PGRs broadly divided based on function?	Two groups.
114	Name the plant growth-promoting PGRs.	Auxins, gibberellins, and cytokinins.
115	Which activities are promoted by growth-promoting PGRs?	Cell division, cell enlargement, pattern formation, tropic growth, flowering, fruiting, and seed formation.
116	Which PGR mainly acts as a growth inhibitor?	Abscisic acid (ABA).
117	Ethylene largely acts as what type of regulator?	Growth inhibitor.
118	The discovery of major groups of PGRs was mostly what kind of event?	Accidental.
119	Who observed phototropism in coleoptiles of canary grass?	Charles Darwin and Francis Darwin.
120	What is phototropism?	Growth towards the light source.
121	Which part of the coleoptile was identified as the site of transmittable influence?	Tip of the coleoptile.
122	Who isolated auxin from oat seedling coleoptile tips?	F.W. Went.
123	Who reported symptoms of bakanae disease using sterile fungal filtrates?	E. Kurosawa (1926).
124	Which active substance was later identified from bakanae disease studies?	Gibberellic acid.
125	What is callus in plant tissue culture?	A mass of undifferentiated cells.
126	Who identified and crystallised kinetin?	Miller et al. (1955).
127	Name the three inhibitors later identified as abscisic acid.	Inhibitor-B, abscission II, and dormin.
128	Who confirmed the release of a volatile ripening substance from oranges?	H.H. Cousins (1910).
129	Which gaseous PGR hastens ripening of bananas?	Ethylene.
130	What is the meaning of the term auxin?	Auxin refers to indole-3-acetic acid (IAA) and related compounds with growth-regulating properties.
131	From where are auxins generally produced in plants?	Growing apices of stems and roots.
132	Name two natural auxins isolated from plants.	Indole-3-acetic acid (IAA) and indole butyric acid (IBA).
133	Name two synthetic auxins.	NAA (naphthalene acetic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid).
134	What is a major application of auxins in plant propagation?	Initiation of rooting in stem cuttings.
135	What role do auxins play in fruit and leaf drop?	They prevent early fruit and leaf drop but promote abscission of older mature leaves and fruits.
136	What is apical dominance?	Inhibition of lateral bud growth by the growing apical bud.
137	What happens after removal of shoot tips (decapitation)?	Growth of lateral buds occurs.
138	In which agricultural practices is decapitation widely used?	Tea plantations and hedge-making.
139	Which hormone induces parthenocarpy in tomatoes?	Auxins.
140	Which synthetic auxin is widely used as a herbicide?	2,4-D.
141	Which type of weeds are killed by 2,4-D?	Dicotyledonous weeds.
142	Why does 2,4-D not affect mature monocotyledonous plants?	Because it selectively acts on dicotyledonous weeds.
143	What is the use of 2,4-D in gardening?	Preparation of weed-free lawns.
144	Auxin controls differentiation of which tissue?	Xylem differentiation.
145	Gibberellins belong to which category of PGRs?	Promotory PGRs.
146	Approximately how many gibberellins are known?	More than 100 gibberellins.
147	How are gibberellins denoted?	As GA1, GA2, GA3, and so on.
148	Which gibberellin is most intensively studied?	Gibberellic acid (GA3).
149	What is the nature of all gibberellins?	Acidic.
150	How are gibberellins used in grapes?	To increase the length of grape stalks.
151	What effect do gibberellins have on apples?	They elongate fruits and improve shape.
152	How do gibberellins affect senescence?	They delay senescence.
153	Why can fruits remain longer on trees after gibberellin treatment?	Because gibberellins delay senescence and extend the market period.
154	What is the use of GA3 in the brewing industry?	To speed up the malting process.
155	How do gibberellins increase sugarcane yield?	By increasing stem length.
156	By how much can gibberellins increase sugarcane yield?	Up to 20 tonnes per acre.
157	What effect do gibberellins have on juvenile conifers?	They hasten maturity and lead to early seed production.
158	What is bolting?	Internode elongation just prior to flowering.
159	In which plants do gibberellins promote bolting?	Beet, cabbages, and rosette plants.
160	Cytokinins were first discovered as which compound?	Kinetin.
161	From where was kinetin obtained?	Autoclaved herring sperm DNA.
162	Does kinetin occur naturally in plants?	No.
163	Which natural cytokinin was isolated from corn kernels and coconut milk?	Zeatin.
164	Where are natural cytokinins synthesised in plants?	In regions where rapid cell division occurs, such as root apices, developing shoot buds, and young fruits.
165	What role do cytokinins play in leaves?	They help produce new leaves and chloroplasts in leaves.
166	How do cytokinins affect apical dominance?	They help overcome apical dominance.
167	What is the role of cytokinins in nutrient mobilisation?	They promote nutrient mobilisation and delay leaf senescence.
168	What is ethylene?	A simple gaseous plant growth regulator (PGR).
169	In which tissues is ethylene synthesised in large amounts?	Tissues undergoing senescence and ripening fruits.
170	Name three effects of ethylene on seedlings.	Horizontal growth, swelling of the axis, and apical hook formation in dicot seedlings.
171	What effect does ethylene have on plant organs?	It promotes senescence and abscission of plant organs, especially of leaves and flowers.
172	What is the role of ethylene in fruit ripening?	Ethylene is highly effective in fruit ripening.
173	What is respiratory climactic?	The rise in the rate of respiration during ripening of fruits.
174	How does ethylene affect seed and bud dormancy?	It breaks seed and bud dormancy.
175	Which seeds show germination initiation by ethylene?	Peanut seeds.
176	What effect does ethylene have on potato tubers?	It initiates sprouting.
177	How does ethylene help deep-water rice plants?	It promotes rapid internode and petiole elongation to keep shoots above water.
178	What effect does ethylene have on roots?	It promotes root growth and root hair formation.
179	Why does ethylene-induced root hair formation help plants?	It increases the absorption surface.
180	How is ethylene used in pineapple cultivation?	To initiate flowering and synchronise fruit-set.
181	Ethylene induces flowering in which fruit plant?	Mango.
182	Which compound is the most widely used source of ethylene?	Ethephon.
183	How does ethephon release ethylene in plants?	It is absorbed and transported within the plant and slowly releases ethylene.
184	What effect does ethephon have on tomatoes and apples?	It hastens fruit ripening.
185	What agricultural process is accelerated by ethephon in flowers and fruits?	Abscission.
186	In which crops is ethephon used for thinning?	Cotton, cherry, and walnut.
187	How does ethephon increase cucumber yield?	By promoting female flowers.
188	What was ABA initially discovered for?	Regulating abscission and dormancy.
189	What type of regulator is abscisic acid (ABA)?	A general plant growth inhibitor and inhibitor of plant metabolism.
190	What effect does ABA have on seed germination?	It inhibits seed germination.
191	How does ABA affect stomata?	It stimulates stomatal closure.
192	Why is ABA called the stress hormone?	Because it increases tolerance of plants to various stresses.
193	What role does ABA play in seeds?	It helps in seed development, maturation, and dormancy.
194	How does ABA help seeds survive unfavourable conditions?	By inducing dormancy, helping seeds withstand desiccation and adverse conditions.
195	ABA acts antagonistically to which hormone in most situations?	Gibberellins (GAs).
196	What would happen if GA3 is applied to rice seedlings?	Rice seedlings would show excessive elongation growth similar to bakanae disease symptoms.
197	What may happen if dividing cells stop differentiating?	Proper maturation and specialised tissue formation would not occur.
198	What happens when a rotten fruit is mixed with unripe fruits?	The unripe fruits ripen faster due to ethylene released from the rotten fruit.
199	What would happen if cytokinin is not added to the culture medium?	Cell division and callus proliferation would be affected.
200	Which plant growth regulator is represented by GA3?	Gibberellic acid.
201	Which gaseous hormone causes rapid ripening of nearby fruits?	Ethylene.
202	Cytokinin mainly promotes which cellular process?	Cell division (cytokinesis).