Meristematic tissue has a number of defining features, including small cells, thin cell walls, large cell nuclei, absent or small vacuoles, and no intercellular spaces. The apical meristem (the growing tip) functions to trigger the growth of new cells in young seedlings at the tips of roots and shoots and forming buds. Statement (ii) is Presence of large vacuole but merismetic tissues have no vacuole which is not correct. statement (ii) not correct. Statement (vii) is Maximal size in wall thickening while merismetic tissues thin cell walls, statement (vii) not correct Answer:(c)

Answer:(b)

Answer:(a)

System (i) Increase in area = 48-12 = 36 Thus percentage growth = 36/12 =300% System (ii) Increase in area =10-5 = 5 Thus percfentage growth =5/5 =100% Answer:(d)

Imbibition uptake of water by a plant or seed. Gibberellins cause seed germination by breaking the seed's dormancy and acting as a chemical messenger. Its hormone binds to a receptor, and calcium activates the protein calmodulin, and the complex binds to DNA, producing an enzyme to stimulate growth in the embryo. During seed germination, 13S globulin is hydrolyzed by proteolytic enzymes through stages and the products are used by the growing seedling. Cytokinines promote nutrient mobilisation, which helps in the delay of leaf senescence. Embryogenesis, the formation of a multicellular embryo from a single-celled zygote, is one of the most dramatic and best-characterized aspects of plant development. The primary root, or radicle, is the first organ to appear when a seed germinates. The plumule is the part of a seed embryo that develops into the shoot bearing the first true leaves of a plant. Answer:(c)

Answer:(c)

Harvested leafy vegetables shows leaf senescence. Cytokinin slows down the process of senescence. Hence harvested leafy vegetables remain fresh Answer:(b)

Answer : (c)

Answer : (d)

Answer : (b)

Gibberellin are a group of diterpenoid growth hormones strongly associated with promoting growth, including stem elongation and germination, Gibberellin Promotes Bolting and Flowering The compound gibberellic acid, which is used in the malting industry to increase enzyme production and accelerate endosperm modification. The apical bud produces a hormone, auxin, (IAA) that inhibits growth of the lateral buds further down on the stem towards the axillary bud. synthetic auxins include the following herbicide families: benzoic acids, phenoxycarboxylic acids, pyridine carboxylic acids, and quinoline carboxylic acids that act similar to that of endogenous plant auxin. Drought stress triggers an increase in the level of the plant hormone abscisic acid (ABA), which initiates a signaling cascade to close stomata and reduce water loss. Answer:(d)

growth is measureable. Parameters for growth : Growth is measured by a variety of parameters some of which are increase in fresh weight, dry weight, length, area, volume cell and growth in number of cells. For example Growth by increase in the number of the cells : Maize root apical meristem can give rise to more than 17, 500 new cells per hour.Growth in size : Cells of watermelon may increase in size by upto 3,50,000 times. Growth in length : Growth of pollen tube is measured in terms of its length. Growth in surface area : An increase in surface area denotes the growth in a dorsiventral leaf. Answer:(c)

Rice is a short-day plant, Statement (i) is correct Abscisic acid is called stress hormones Statement (ii) is NOT correct Photoperiodism is the physiological reaction of organisms to the length of night or a dark period. Statement (iii) is correct. Embryonic ABA plays a central role in induction and maintenance of seed dormancy and also inhibits the transition from embryonic to germination growth. Statement (iv) is correct. Answer:(c)

Gibberellic acid is a plant hormone. it is used to speed up malting process, is used in brewery industry. Auxin is a plant hormone which is used to induce flowering in pineapple as it induces synthesis of ethylene. Cytokinin is a plant hormone that stimulates cell division. It delays the senescence in leaves Answer:(c)

Coleoptiles are cylindrical organs that ensheath the first leaf and shoot apex in grass seedlings. They help in the emergence of the first leaf (and shoot apex) by protecting it during its passage through the soil. On emergence, the first leaf breaks through the coleoptile tip. A chemical messenger or hormone called auxin moves down the dark side of the shoot and stimulates growth on that side. The model proposes that auxin, a plant growth hormone, is synthesized in the coleoptile tip, which senses light or gravity and will send the auxin down the appropriate side of the shoot. Answer:(d)

Auxins induce cell elongation. In a differentially illuminated plant, they accumulate in the shaded part, causing elongation of the cells in the shaded part. This unequal elongation on two sides causes the plant to curve or bend towards the light source i.e., phototropic curvature Answer:(b)

Etiolation is the abnormal form of growth observed when plants grow in darkness or severely reduced light. Such plant characteristically have branched leaves and shoots, excessively long shoots and reduced leaves and root systems Answer:(c)

NAA (a-Naphthalene acetic acid) and 2,4 D (2, 4 dichlorophenoxy acetic acid) are synthetic auxins. Normally, auxins inhibit flowering. In lettuce, it delays flowering and the plants can be kept in their vegetative phase for longer periods of time. In litchi and pineapple, however, application of auxin promotes flowering. Answer:(a)

Light and temperature may affect flowering in plants in various ways. The effect of photoperiods or daily duration of light hours-(and dark periods) on flowering is called photoperiodism. For example, in short day plants flowering occurs when day length is below critical period, e.g., dahlia, rice etc. In long day plants, flowering occurs when day length is above critical period, e.g., spinach, lettuce etc. In short-long day plants, short photoperiod is required for oral initiation and long photoperiod is required for blossoming and viceversa for long-short day plants. Photoperiodic response is mediated by phytochrome, a pigment which perceives the photoperiod stimulus in leaves. It shows reversible change in red and far-red wavelength. Besides correct photoperiod, some plants require low temperature for flowering. These plants remain vegetative during the warm season flower in winters on receiving low temperature. This was found by Lysenko, that the cold requiring annual and biennial plants can be made to flower in one growing season by providing low temperature treatment (vernalization). Stimulus of vernalization is perceived by meristematic cells, e.g., shoot | tips, root apex, etc., and is named as vemalin. Answer:(b)

Gibberellins & ABA are antagonistic with each other. ABA counteracts many effects of a gibberellins like induction of hydrolases and alpha-amylases in barley seedlings. Answer:(c)

Carrot is a biennial plant that requires stimulus of low temperature for flowering. It remains vegetative during the warm season and bears flowers and fruits only during winter. It can be made to flower in one growing season by providing low temperature treatment to young plants or seedlings which is referred to as vernalization. Hence, vernalization stimulates flowering in carrot. Answer:(c)

Phototropic curvature is the result of uneven distribution of auxin. Charles Darwin and his son Francis Darwin observed that the coleoptiles of canary grass responded to unilateral illmination by growing towards the light source (phototropism). After a series of experiments, it was concluded that the tip of coleoptile contain auxin that caused the bending of the entire coleoptile in relation to the direction of light. Answer:(d)

The growth movement in response to touch, or contact of a foreign body, in plants is called thigmotropism or thigmotropic movement. The stems and tendrils of the climbers are positively thigmotropic in their response. The coiling of garden pea tendrils around any support is an example of thigmotropism. Thigmonastic (haptonastic) movements are induced by some external stimuli. For example tentacles of Drosera leaf curve and the lamina lobes of Dionaea fold on coming in contact with an insect. Answer:(c)

Indole-3-acetic acid (also called auxin) is a phytohormone which is generally produced by the growing apices of the stems and roots, from where they migrate to the regions of their action. It is observed that the growing apical bud inhibits the growth of the lateral (axillary) bud. (apical dominance). Since apical meristem is the site of auxin synthesis, it is the physiological effect of the auxin which results in the phenomenon of apical dominance. When shoot tips is removed it usually results in the growth of lateral buds. This phenomenon is widely applied in tea plantations and hedge-making because as in tea plantation and industries, the apical bud is plucked for tea processing which results in more lateral buds thus enhancing plantation and further industrial purposes. Answer:(d)

Ethylene promotes root growth and root hair formation. In low concentration ethylene is used for initiation of roots and also of lateral roots Answer:(d)

(c & d) Many auxins have been synthesized which have similar properties with natural auxin and some examples of synthetic auxins are indole-3-butyric acid (IBA), naphthalene acetic acid (NAA), 2,4-dichloro- phenoxy acetic acid(2,4-D), 2,4,5-trichloro-phenoxyacetic acid (2,4,5 -T). Answer:(c, d)

Biosynthesis of abscisic acid (ABA) in most plants occur indirectly by degradation of certain carotenoids present in chloroplasts or other plastids. The biosynthetic pathway follow mevalonic acid pathway for their synthesis. The sites of synthesis are fruits, tissues, leaves, roots and seeds. Answer:(c)

The effect of photoperiods or daily duration of light hours (and dark periods) on the growth and development of plants, especially flowering, is called photoperiodism. Photoperiodism was rst studied by Gamer and Allard (1920). They observed that ‘Maryland Mammoth’ variety of tobacco could be made to lower in summer by reducing the light hours with artificial darkening. It could be made to remain vegetative in winter by providing extra light. Answer:(d)

Senescence is the process of ageing which is caused by cellular breakdown, increased metabolic failure, increased entropy etc. It occurs in the period between reproductive maturity and death. Cell division followed by cell enlargement and differentiation, precede the actual separation. Senescence of cell in distal region lead to lignification of cell wall. Tylose formation in tracheary element and callose deposition in sieve elements which occur in advance of abscission (i.e. senescence) finally, lead to actual separation. Thus, vessels and tracheid (trachery elements) differentiation indicates senescence. Answer:(c)

Phytochrome is the photoreceptor pigment that controls flowering. It has two forms as P and P . P is bluish phytochrome and it absorbs light at 660 to 680 nm of wavelength. P is (far red) yellowish green and absorbs light at 730 nm of wavelength Answer:(a)

Gibberellic acid is a simple weakly acidic plant growth hormone which promotes cell elongation of both leaves and stems in general and intemodal length of genetically dwarf plants in particular. It is in general a growth promoting hormone and does not inhibit growth. So leaf abscission is not associated with gibberellic acid but with abscisic acid. Answer:(a)

The process by which the dormant embryo of seed resumes active growth and forms a seedling is known as germination. The initial step in germination process is the uptake of water and rehydration of the seed tissues by the process of imbibition. The firrst visible sign of germination is the emergence of the radicle from the seed. But this event is preceded by a series of biochemical reactions. Imbibition of water causes the embryo within seed to produce α and β-amylases. These enzymes hydrolyze the starch stored in endosperm into glucose which is necessary for use both as a respiratory substrate and as a source of carbon skeletons of the molecules needed for growth. Answer:(b)

Nitrogen is the fourth most abundant element. Chief source of Nitrogen for plants is nitrates of Ca and K. It is important for plants as it is a component of nucleic acids, proteins chlorophyll and cytochromes. Deficiency of nitrogen causes poor root development, lower respiration rate, chlorosis of older leaves etc. Cytokinins are also very important for plant development. They are associated with the control of apical dominance, fruit development, root growth, cambial activity. So a nitrogenous fertilizer like NPK and Cytokinins are most beneficial to the plant. Answer:(c)

Thigmonastic movements are exhibited by some insectivorous plants such as Dionaea, venus fly trap, Drosera etc. These plants have tentacles, which are sensitive to the stimulus of touch. In the case of the venus fly trap turgor pressure changes occur in which hydrogen ions are rapidly pumped into the walls of cells on the outside of each leaf in response to the action potentials from the trigger hairs. The protons apparently loosen the cell walls so rapidly that the tissue actually becomes flaccid so that cells quickly absorb water, causing the j outside of each leaf to expand and the trap to snap shut. Answer:(d)

Answer:(a)

Answer:(a)

Gibberellins play a role in the elongation of intemodes in ‘rosette’ plants. Before reproductive stage there is too much elongation of intemodes but there is less leaf formation. An elongated intemode without leaves in called a “bolt” like structure and the process is called “bolting” flowering takes place after bolting. Gibberellins induce cell division and cell elongation, when bolting takes place. Answer:(c)

Plants require a day length or light period for flowering, this light period is called as photoperiod. It was ; first studied by Gamer and Allard (1920). Short day plants (SDP’s) flower in photoperiods less than critical day length, e.g., Nicotiana tabacum, Glycine max (Soybean), Xanthium strumarium. Further these plants require long uninterrupted dark period and hence are called long night plants. Long day plants (LDP’s) flower in photoperiod more than critical day length, e.g., Hyocyamus niger (Henbane), radish, Beta, spinach, Plantago, etc. Day neutral plants flower in any photoperiod, e.g., tomato, maize, cucumber, etc. Answer:(d)

According to biological species concept a species is a natural inbreeding or panmictic species or group of natural populations which have essentially similar morphological traits, they are genetically distinct and reproductively isolated from others. Since under laboratory conditions N. tabacum and N. sylvestris can produce self- fertile offspring so they are not reproductively isolated. They are considered as separate species because since their flowering periods are different so cross pollination is not possible between them naturally. This makes them different species. Answer:(a)

Zinc is available to the plants for absorption in the divalent form. It occurs in the form of minerals as hornblende, magnetite, biotite etc., from where it is released by weathering. It is involved in the synthesis of Indole-acetic acid in plants. It is an activator in the enzyme tryptophan synthetase. Tryptophan is the precursor of Indole-acetic acid. Answer:(a)

Synthetic auxins are employed for Killing weeds. Examples 2,4-D and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), Synthetic Auxins and Auxin Transport Inhibitors are generally used for controlling broadleaf weeds in grass crops, pastures, and industry. These herbicides include some of the more effective chemicals for perennial broadleaf weed and brush control. Answer:(c)

it was proved experimentally that (i) High cytokinins/auxin ratio – Differentiation of shoot. (ii) Low cytokinins/auxin ratio-Differentiation of root. (iii) Intermediate cytokinins/auxin ratio – Differentiation of both root and shoot. (iv) Intermediate cytokinins/low auxin – Callus formation. Answer:(b)

Viable seeds of some plants are unable to germinate even after getting all the” necessary conditions. This inability of viable seeds to germinate even under favorable conditions, is called dormancy of seeds. This is considered to be due to some barriers or blocks inside the seeds. Some common causes of seed dormancy are 1. Mechanically hard seed coat, which does not allow proper growth of embryo inside it, e.g., Brassica campestris. 2. Presence of impermeable (impervious) seed coat to H20, e.g. many seeds of legumes. 3. Presence of impermeable seed coat to oxygen, e.g. Xanthium (cocklebur). 4. Presence of germination inhibitors like ABA (abscisic acid) and phenolics, etc., in seed coat or fruit pulp, e.g., in tomato, inhibitor is present in fruit pulp. Seed coats may contain relatively high concentrations of growth inhibitors that can suppress germination of the embryo. Abscisic acid (ABA) is a common germination inhibitor present in the seed coats. Repeated washing and heavy rainfall removes such substances from the seed coat. Answer:(b)

Giberellins helps in the reversal of dwarfism in many genetically dwarf plants. External supply of Gibberellic acid causes rapid elongation of growth, e.g. Rosette plant of sugarbeet when treated with GA undergoes marked longitudinal growth of axis. Answer:(b)

Plants require a day length or light period for flowering, this light period is called as photoperiod. It was ; first studied by Gamer and Allard (1920). Short day plants (SDP’s) flower in photoperiods less than critical day length, e.g., Nicotiana tabacum, Glycine max (Soybean), Xanthium strumarium. Further these plants require long uninterrupted dark period and hence are called long night plants. Long day plants (LDP’s) flower in photoperiod more than critical day length, e.g., Hyocyamus niger (Henbane), radish, Beta, spinach, Plantago, etc. Day neutral plants flower in any photoperiod, e.g., tomato, maize, cucumber, etc. Answer:(d)

a-Naphthalene acetic acid (NAA) is a synthetic or exogenous auxin. It prevent the formation of abscission layer, which is a layer of dead cells in the petiole and pedicel that causes fall of leaf or fruit. NAA prevents formation of this layer and so it prevents fall of leaf or fruit. Answer:(b)

Abscisic acid is a growth inhibiting phytohormone. It induces senescence in leaves by promoting the degradation of chlorophyll and proteins. Auxin is a growth promoting phytohomone that results in cell division, cell enlargement and apical dominance. Cytokinin is a growth promoting phytohormone that causes cell division, morphogenesis and seedling growth. Gibberellins are growth promoting phytohormone that results in overcoming seed dormancy and bolting. Answer:(a)

Gibberellin is the hormone that breaks seed/ bud dormancy. The tubers of potato reproduce vegetative to give rise to new plants. So the dormancy of these tubers can be overcome by applying gibberellins Answer:(a)

Apical dominance is the phenomenon by which presence of apical bud does not allow the nearby lateral buds to grow. When apical bud is removed, the lateral buds sprout. Answer:(a)

Answer:(b)