Anatomy of Flowering Plants

Transcription

1 76 Anatomy of Flowering Plants 1. Tunica corpus theory is connected with (a) root apex (b) root cap (c) shoot apex (d) secondary growth The shoot apex or stem apical meristem has two zones, outer tunica and inner corpus. This theory was given by Schmidt Which meristem helps in increasing girth? (a) Lateral meristem (b) Intercalary meristem (c) Primary meristem (d) Apical meristem Lateral meristems occur on the sides of stem and help in increasing girth of stem and root. It divides only periclinally or radially and is responsible for increase in girth or diameter. 3. Which one yields fibres? [1988] (a) Coconut (b) Oak (c) Teak (d) Sisso Commercial fibres are obtained from Cocos nucifera (coconut) also called surface fibres and occur on surface of seeds. 4. Cork is formed from [1988] (a) cork cambium (phellogen) (b) vascular cambium (c) phloem (d) xylem Phellogen present in outer cortical cells produces cork or phellem on the outer side which consists of dead and compactly arranged rectangular cells that possess suberised cell walls. Which causes them to become buoyant. Phellogen also cuts off cells on innerside called as phelloderm or secondary cortex. 5. Pith and cortex do not differentiate in [1988] (a) monocot stem (b) dicot stem (c) monocot root (d) dicot root The ground tissue in monocot stem do not show distinction into cortex, endodermis, pericycle, pith and pith rays. 6. Organisation of stem apex into corpus and tunica is determined mainly by [1989] (a) planes of cell division (b) regions of meristematic activity (c) rate of cell growth (d) rate of shoot tip growth Cells of tunica divide anticlinally to form the outer layer, cells of corpus undergo division in different planes. 7. Death of protoplasm is a pre-requisite for a vital function like [1989] (a) transport of sap (b) transport of food (c) absorption of water (d) gaseous exchange Xylem performs the function of transport of water or sap inside the plant and it is a dead tissue i.e. devoid of protoplasm. 8. Sieve tubes are suited for translocation of food because they possess [1989] (a) bordered pits (b) no ends walls (c) broader lumen and perforated cross walls (d) no protoplasm Sieve tubes are elongated tubular conducting channels of phloem. The end walls possess many small pores and have thin cellulosic wall. The lumen is broad in nature. 9. Which is the correct fact about diffuse or ring porous wood? [1989] (a) Ring porous wood, carries more water for short period

2 77 (b) Diffuse porous wood carries more water (c) Ring porous wood carries more water when need is higher (d) Diffuse porous wood is less specialised but conducts water rapidly throughout Ring porous wood is more advanced than diffuse porous wood as it provides for better translocation when requirement of plant is high. 10. Cork cambium and vascular cambium are [1990, 95] (a) parts of secondary xylem and phloem (b) parts of pericycle (c) lateral meristems (d) apical meristems Cork cambium and vascular cambium are responsible for secondary growth which increases the girth of the stem. 11. Monocot leaves possess [1990] (a) intercalary meristem (b) lateral meristem (c) apical meristem (d) mass meristem Intercalary meristems are derived from apical meristems and separated from the same by permanent cells. They are responsible for localised growth. 12. Collenchyma occurs in the stem and petioles of [1990] (a) Xerophytes (b) Monocots (c) Dicot herbs (d) Hydrophytes Collenchyma provides mechanical strength to young dicot stems, petioles and leaves. 13. Collenchyma occurs in [1990] (a) herbaceous climbers (b) woody climbers (c) climbing stems (d) water plants Collenchyma is abundant in climbing stems providing mechanical strength. 14. Pericycle of roots produces [1990] (a) mechanical support (b) lateral roots (c) vascular bundles (d) adventitious buds Pericycle in roots is active in the formation of root branches or lateral roots. 15. For union between stock and scion in grafting which one is the first to occur? [1990] (a) Formation of callus (b) Production of plasmodesmata (c) Differentiation of new vascular tissues (d) Regeneration of cortex and epidermis In grafting, union between stock and scion produces undifferentiated mass of cells called callus. Grafting is a method of plant propagation widely used in horticulture, where the tissues of one plant are encouraged to fuse with those of another. It is most commonly used for the propagation of trees and shrubs grown commercially. Grafting is limited to dicots and gymnosperms. Monocots lack the vascular cambium required. 16. What is true about a monocot leaf [1990] (a) Reticulate venation (b) Absence of bulliform cells from epidermis (c) Mesophyll not differentiated into palisade and spongy tissues (d) Well differentiated mesophyll In monocot leaves, the mesophyll cells are undifferentiated. 17. Vascular cambium produces [1990, 92] (a) primary xylem and primary phloem (b) secondary xylem and secondary phloem (c) primary xylem and secondary phloem (d) secondary xylem and primary phloem

3 78 Vascular cambium produces secondary xylem on the inner side and secondary phloem to the outer side. 18. Where do the casparian bands occur? [1990, 94] (a) Epidermis (b) Endodermis (c) Pericycle (d) Phloem Endodermis or innermost layer of cortex has casparian strips in roots. It is called starch sheath in dicot stems. It separate cortex from stele. The cell walls are thickened at the corners in angular collenchyma. 19. Angular collenchyma occurs in [1991] (a) Cucurbita (b) Helianthus (c) Althaea (d) Salvia With providing mechanical strength, collenchyma also provides flexibility to the organ and allow their bending eg.: Cucurbita. 20. An organised and differentiated cellular structure having cytoplasm but no nucleus is [1991] (a) Vessels (b) Xylem parenchyma (c) Sieve tubes (d) Tracheids Internally, sieve tubes possess peripheral layer of cytoplasm and are devoid of nucleus. They are living cells. Cell walls of sieve tubes are thickened than surrounding parenchyma cells. 21. Which is correct about transport or conduction of substances? [1991] (a) Organic food moves up through phloem (b) Organic food moves up through phloem (c) Inorganic food moves upwardly and downwardly through xylem (d) Organic food moves upwardly and downwardly through phloem Sieve tubes are long distance channels for transport of organic nutrients. The movement of the nutrients are bidirectional. 22. Commercial cork is obtained from [1991] (a) Berberis/Barberry (b) Salix/Willow (c) Quercus/Oak (d) Betula/Birch Quercus suber (Cork oak or Bottle cork) possess cork cells. Cork cells are dead, suberized and impervious to water and air, compactly arranged with no intercellular spaces. 23. A bicollateral vascular bundle is characterised by [1992] (a) Phloem being sandwitched between xylem (b) Transverse splitting of vascular bundle (c) Longitudinal splitting of vascular bundle (d) Xylem being sandwitched between phloem Bicollateral vascular bundles have phloem in both outer and inner side of xylem. These type of bundles occur in cucurbitaceae. 24. Bordered pits are found in [1993] (a) Sieve cells (b) Vessel wall (c) Companion cells (d) Sieve tube wall The walls of xylem vessels are lignified and bordered pits are common in the walls. 25. Abnormal/anomalous secondary growth occurs in [1993] (a) Dracaena (b) Ginger (c) Wheat (d) Sunflower Abnormal secondary growth occurs in some arborescent monocots (eg.: Dracaena, Yucca) 26. Which exposed wood will decay faster

4 79 (a) Sapwood (b) Softwood (c) Wood with lot of fibres (d) Heartwood Sapwood is less durable because it is susceptible to attack by pathogen and insects. It is physiologically active and conduction of water takes place through it. Heartwood is not attacked by pathogens and insects as it is physiologically inactive. It is filled with tannins, resins and gums which are not preferred by insects and pathogens. 27. A narrow layer of thin walled cells found between phloem/bark and wood of a dicot is [1993] (a) Cork cambium (b) Vascular cambium (c) Endodermis (d) Pericycle Vascular cambium is produced by two types of meristems, fascicular and interfascicular cambium. 28. Periderm is produced by [1993] (a) Vascular cambium (b) Fascicular cambium (c) Phellogen (d) Intrafascicular cambium Secondary ground tissue or periderm is formed from phellogen or cork cambium. The phellogen forms phellem on the outer face and phelloderm on the inner. The three layers i.e., phellem, phellogen and phelloderm jointly constitute the periderm. 29. Procambium forms [1994] (a) only primary vascular bundles (b) only vascular cambium (c) only cork cambium (d) primary vascular bundles and vascular cambium Procambium is the derivative of shoot apical meristem and forms vascular strand. 30. As the secondary growth takes place (proceeds) in a tree, thickness of [1994] (a) heart wood increases (b) sap-wood increases (c) both increase (d) both remain the same Heartwood is the central wood of mature dicot stem and is the nonfunctional part of secondary xylem. 31. What is not true about sclereids? [1996] (a) These are parenchyma cells with thickened lignified walls (b) These are elongated and flexible with tapered ends (c) These are commonly found in the shells of nuts and in the pulp of guava, pear, etc (d) These are also called the stone cells Sclereids are small bundles of sclerenchyma tissue in plants that form durable layers, such as the cores of apples and the gritty texture of pears. Sclereids are variable in shape. The cells can be isodiametric, prosenchymatic, forked or fantastically branched. The cell walls fill nearly all the cell s volume. The shell of many seeds like those of nuts as well as the stones of drupes like cherries or plums are made up from sclereid. 32. At maturity which of the following is enucleate? [1997] (a) Sieve cell (b) Companion cell (c) Palisade cell (d) Cortical cell At maturity all physiological functions of sieve tube takes place in companion cell, since the sieve tube elements lose their nucleus at maturity. 33. A leaf primordium grows into the adult leaf lamina by means of [1998] (a) apical meristem (b) lateral meristem (c) marginal meristems (d) at first by apical meristem and later largely by marginal meristems. A leaf primordium grows into the adult leaf lamina by means of first by apical meristem and later by marginal meristems.

5 Which of the following meristems is responsible for extrastelar secondary growth in dicotyledonous stem? [1998] (a) Intrafascicular cambium (b) Interfascicular cambium (c) Intercalary meristem (d) Phellogen Intrafascicular cambium occurs inside the vascular bundles in between xylem and phloem. Interfascicular cambium develops in the form of strips at the level of intrafascicular cambium of vascular bundles. Intercalary meristem lie in between areas of permanent tissues. 35. Transition of radial vascular bundle in root to conjoint vascular bundle in stem occurs in which zone? [1999] (a) Epicotyl (b) Hypocotyl (c) Meristem (d) At base of stem Transition of radial vascular bundle in root to conjoint vascular bundle in stem occurs in transition zone which is generally hypocotyl. Hypocotyl is the part of embryonal axis below the level of cotyledons. 36. What happens during vascularization in plants? [2000] (a) Differentiation of procambium is immediately followed by the development of secondary xylem and phloem (b) Differentiation of procambium followed by the development of xylem and phloem (c) Differentiation of procambium, xylem and phloem is simultaneous (d) Differentiation of procambium followed by the development of primary phloem and then by primary xylem Vascularization of plant means the development of vascular bundle in the plant, which develops from the cambium. 37. Loading of pholem is related to [2001] (a) increases of sugar in phloem (b) elongation of phloem cell (c) separation of phloem parenchyma (d) strengthening of phloem fibre Phloem is involved in transport of organic food. According to mass flow hypothesis organic substances flow in solution form in sieve elements due to development of an osmotically generated pressure gradient. 38. Main function of lenticel is [2002] (a) transpiration (b) guttation (c) gaseous exchange (d) bleeding Lenticels are pores present in woody stem through which transpiration or loss of water vapour takes place. Lenticel formation begins during the development of the first periderm. In the stem, they usually appear below a stoma or group of stomata. It should also be noted that lenticels can be present on fruits such as apples and pears. 39. Vessels are found in [2002] (a) all angiosperms and some gymnosperms (b) most of angiosperms and few gymnosperms (a) all angiosperms, all gymnosperms and some pteriodophyta (d) all pteridophyta Generally gymnosperms do not have vessels but a few gymnosperms having vessels are Ephedra, Smilax etc. Most of angiosperms have vessels except of few e.g., Trochodendron. 40. Four radial vascular bundles are found in [2002] (a) dicot root (b) monocot root (c) dicot stem (d) monocot stem When xylem and phloem strands are present at different radii the vascular bundles are radial and 4 radial vascular

6 81 bundles (tetrach condition) are present in dicot root. This is called tetrach conditions. 41. Axillary bud and terminal bud are derived from the activity of [2002] (a) lateral meristem (b) intercalary meristem (c) apical meristem (d) parenchyma Apical meristem is located at the apex of stem, root and their branches and forms axillary bud & terminal bud. Intercalary meristems take part in linear growth. Lateral meristem occur parallel to the circumference of the organs. They increase girth of the plant. 42. Which of the following statements is true? [2002] (a) Vessels are multicellular with narrow lumen (b) Tracheids are multicellular with narrow lumen (c) Vessels are unicellular with wide lumen (d) Tracheids are unicellular with wide lumen Vessels are elongated, multicellular water conducting channels with wide lumen formed by end to end fusion of a large number of vessel elements. Tracheids are elongated dead cells with tapering ends having lignified walls and large or wide lumen. Their main function is conduction of water and minerals from root to leaf. 43. The cells of the quiescent centre are characterised by [2003] (a) dividing regularly to add to tunica (b) having dense cytoplasm and prominent nuclei (c) having light cytoplasm and small nuclei (d) dividing regularly to add to the corpus The cells of queiscent centre have lower concentration of DNA, RNA and protein as compared to other cells in the root apex. These cells do not divide, hence cytoplasm is light and nuclei are small in them. This concept is based upon quiescent centre theory proposed by Clowes (1961). 44. The apical meristem of the root is present (a) in all the roots (b) only in radicals (c) only in tap roots (d) only in adventitious roots The apical meristem of the root is present at all the root tips. Apical meristem is subterminal in position of the growing root tips and responsible for terminal growth of the root of plants. 45. Chlorenchyma is known to develop in the (a) pollen tube of Pinus (b) cytoplasm of Chlorella (c) mycelium of a green mould such as Aspergillus (d) spore capsule of a moss Chlorenchyma cells are those parenchymatous cell which contain chloroplast in them. They are capable of photosynthesis. A spore capsule of moss can perform photosynthesis, therefore chlorenchyma are present in them. 46. In a longitudinal section of a root, starting from the tip upward, the four zones occur in the following order: [2004] (a) Root cap, cell division, cell enlargement, cell maturation (b) Root cap, cell division, cell maturation, cell enlargement (c) Cell division, cell enlargement, cell maturation, root cap (d) Cell division, cell maturation, cell enlargement, root cap Root shows the following regions Root cap or calyptra - caplike protective covering over tip of the root Meristematic region is the subapical position Zone of elongation - receives news cells from the growing point Root hair zone - is the zone of differentiation Zone of mature cells - having thick walled impermeable cells. 47. The most abundant element present in the plants is [2004] (a) Carbon (b) Nitrogen

7 82 (c) Manganese (d) Iron Manganese and Iron are micronutrients required in trace amounts. Concentration of nitrogen in dry matter mg./ gm. Concentration of carbon in dry matter is 45,000 mg/ gm. 48. Ectophloic siphonostele is found in (a) Osmunda and Equisetum (b) Marsilea and Botrychium (c) Adiantum and Cucurbitaceae (d) Dicksonia and Maidenhair fern The central pith is surrounded by xylem, phloem, pericycle and endodermis. The phloem occurs only outside the xylem e.g Equisetum, Osmunda. 49. In a woody dicotyledonous tree, which of the following parts will mainly consist of primary tissues? [2005] (a) All parts (b) Stem and root (c) Flowers, fruits and leaves (d) Shoot tips and root tips Primary Meristems: They are those meristematic tissues which are dervied directly from the meristems of the embryo and retain their meristematic activity. They are present at root, shoot tip and leaf primordia. 50. A common structural feature of vessel elements and sieve tube elements are [2006] (a) pores on lateral walls (b) presence of p-protein (c) enucleate condition (d) thick secondary walls In plant conducting tissue xylem has an important integral cell as xylem vessel which is without nucleus. The phloem on other hand has a row of sieve tubes which are also without nucleus at maturity. 51. For a critical study of secondary growth in plants. Which one of the following pairs is suitable? [2007] (a) teak and pine (b) deodar and fern (c) wheat and maiden hair fern (d) sugarcane and sunflower. Teak and pine is most suitable for the study of critical secondary growth because in secondary growth, secondary tissues are formed from lateral meristem which is well developed in these two cases and secondary growth occurs in gymnosperms and dicots. 52. Passage cells are thin walled cells found in [2007] (a) phloem elements that serve as entry points for substance for transport ot other plant parts (b) testa of seeds to enable emergence of growing embryonic axis during seed germination (c) central region of style through which the pollen tube grows towards the ovary (d) endodermis of roots facilitating rapid transport of water from cortex to pericycle. The innermost leyer of the cortex is called endodermis. It comprises a single layer of barrel shaped cells without any intercellular spaces. In roots thick walled endodermal cells are interrupted by thin walled passage cells or transfusion tissue. 53. Vascular tissues in flowering plants develop from: [2008] (a) phellogen (b) plerome (c) periblem (d) dermatogen Vascular tissues in flowering plants develop from plerome. Plerome is a central core of primary meristem which gives rise to all cells of the stele from the pericycle inward. 54. The length of different internodes in a culm of sugarcane is variable because of [2008] (a) shoot apical meristem (b) position of axillary buds (c) size of leaf lamina at the node below each internode (d) intercalary meristem

8 83 The length of different internodes in a culm of sugarcane is variable because of intercalary meristem. Intercalary meristem is not a part of apical meristem, occurs in the internodes of grasses (sugarcane) between leaf nodes and enables longitudinal growth of the stem. 55. Which one of the following is resistant to enzyme action? [2008] (a) Cork (b) Wood fibre (c) Pollen exine (d) Leaf cuticle Pollen exine is resistant to enzyme action. The hard outer layer called the exine is made up of sporopollenin which is one of the most resistant organic material known. It can withstand high temperatures and strong acids and alkali. No enzymes that degrades sporopollenin is so far known. 56. Anatomically fairly old dicotyledonous root is distinguished from the dicotyledonous stem by [2009] (a) absence of secondary phloem (b) presence of cortex (c) position of protoxylem (d) absence of secondary xylem Anatomically fairly old dicotyledonous root is distinguished from the dicotyledonous stem by position of protoxylem. In dicot root the protoxylem is located near the periphery of the vascular cylinder while in dicot stem the protoxylem is located near the centre of vascular bundle i.e. the xylem is endarch. 57. The annular and spirally thickened conducting elements generally develop in the protoxylem when the root or stem is: [2009] (a) elongating (b) widening (c) differentiating (d) maturing The annular and spirally thickened conducting elements generally develop in the protoxylem when the root or stem is maturing. 58. Palisade parenchyma is absent in leaves of: (a) mustard (b) soybean (c) gram (d) sorghum Palisade parenchyma is absent in leaves of Sorghum. It is a leaf tissue composed of columnar cells containing numerous chloroplasts in which the long axis of each cell is perpendicular to the leaf surface. The palisade parenchyma is usually directly beneath the epidermis of the upper surface of the leaf. The cells of the palisade parenchyma are cylindrical. Neighbouring cells look like the stakes of a palisade. Cells of the palisade parenchyma contain three to five times as many chloroplasts as those of the spongy parenchyma. The chloroplasts stay usually near the cell s wall, since this adjustment guarantees optimal use of light. 59. In barley stem vascular bundles are: [2009] (a) closed and scattered (b) open and in a ring (c) closed and radial (d) open and scattered In barley stem vascular bundles are closed and scattered. They are open only for a hours in the day time and never open at night. e.g Cereals. 60. Reduction in vascular tissue, mechanical tissue and cuticle is characteristic of: [2009] (a) mesophytes (b) epiphytes (c) hydrophytes (d) xerophytes Reduction in vascular tissue, mechanical tissue and cuticle is characteristic of hydrophytes. 61. The chief water conducting elements of xylem in gymnosperms are: [2010] (a) vessels (b) fibres (c) transfusion tissue (d) tracheids

9 84 Tracheids are chief water conducting elements of xylem in gymnosperms. They are devoid of protoplasm and hence dead. The wall constituting the tracheids is hard, thick and lignified. These are elongated cells with tapering ends. 62. Which one of the following is not a lateral meristem? [2010] (a) Intrafascicular cambium (b) Interfascicular cambium (c) Phellogen (d) Intercalary meristem Meristem is divided on the basis of position in plant bodies into apical meristem, lateral meristem and intercalary meristem. Lateral meristem is present on the lateral sides, that is fascicular and interfascicular cambium and cork cambium (phellogen). 63. Heartwood differs from sapwood in: [2010] (a) presence of rays and fibres (b) absence of vessels and parenchyma (c) having dead and non -conducting elements (d) being susceptible to pests and pathogens Heartwood differs from sapwood in having dead and non-conducting elements. In old trees, the inner region that comprises dead elements with highly lignified walls is called heartwood. Heartwood does not conduct water but gives mechanical support to the stem. On the other hand, the peripheral region, which is lighter in colour are called sapwood. It is involved in the conduction of water and minerals from root to leaf. 64. Ground tissue includes [2011] (a) all tissues external to endodermis (b) all tissues except epidermis and vascular bundles (c) epidermis and cortex (d) all tissues internal to endodermis Ground tissue includes all tissues except epidermis and vascular bundles. The ground tissue comprises the bulk of the primary plant body. Parenchyma, collenchyma and sclerenchyma cells are common in the ground tissue. 65. In land plants, the guard cells differ from other epidermal cells in having: [2011] (a) cytoskeleton (b) mitochondria (c) endoplasmic reticulum (d) chloroplasts Guard cells differ from epidermal cells in having chloroplast. The cell wall of guard cells are not uniform, inner walls are thicker than the outer walls, epidermal cells are uniformly thin. 66. The cork cambium, cork and secondary cortex are collectively called: [2011] (a) phelloderm (b) phellogen (c) periderm (d) phellem Phellem, phellogen and phelloderm are collectively called periderm. 67. Which one of the following is wrongly matched? [2011] (a) Root pressure - Guttation (b) Puccinia - Smut (c) Root - Exarch protoxylem (d) Cassia - Imbricate aestivation Smut is a disease of cereals, corn, grasses and sorghum caused by many species of fungi. 68. Function of companion cells is [2011M] (a) providing energy to sieve elements for active transport (b) providing water to phloem (c) loading of sucrose into sieve elements by passive transport (d) loading of sucrose into sieve elements Function of companion cell is to load sugar and amino acids into sieve elements. These cells use transmembrane proteins to take up by active transport.

10 Some vascular bundles are described as open because these [2011M] (a) are surrounded by pericycle but not endodermis (b) are capable of producing secondary xylem and phloem (c) possess conjunctive tissue between xylem and phloem (d) are not surrounded by pericycle Open means presence of cambium during secondary growth. Vascular cambium divides to form secondary xylem towards inner side while secondary phloem towards outside. 70. In Kranz anatomy, the bundle sheath cells have [2011M] (a) thin walls, many intercellular spaces and no chloroplasts (b) thick walls, no intercellular spaces and large number of chloroplasts (c) thin walls, no intercellular spaces and several chloroplasts (d) thick walls, many intercellular spaces and few chloroplasts In Kranz anatomy, the bundle sheath cells have thick wall, no intracellular spaces and large number of chloroplasts. 71. The common bottle cork is a product of: [2012] (a) Dermatogen (b) Phellogen (c) Xylem (d) Vascular Cambium The common bottle cork is the product of phellogen. Phellogen produces cork or phellem on the outer side. It consists of dead and compactly arranged rectangular cells that possess suberised cells walls. The cork cells contain tannins. Hence, they appear brown or dark brown in colour. The cork cells of some plants are filled with air e.g., Quercus suber (Cork Oak or Bottle Cork). 72. Companion cells are closely associated with: [2012] (a) Sieve elements (b) Vessel elements (c) Trichomes (d) Guard cells 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. It is supposed that the nuclei of the companion cells control the activities of the sieve tube through plasmodesmata. Companion cells also help in maintaining a proper pressure gradient in the sieve tube elements. 73. Closed vascular bundles lack [2012] (a) Ground tissue (b) conjunctive tissue (c) Cambium (d) Pith In closed vascular bundle cambium is absent between xylem and phloem. 74. Water containing cavities in vascular bundles are found in: [2012] (a) Sunflower (b) Maize (c) Cycas (d) Pinus Stem of maize has water containing cavities in vascular bundles. 75. Gymnosperms are also called soft wood spermatophytes because they lack: [2012] (a) Cambium (b) Phloem fibres (c) Thick-walled tracheids (d) Xylem fibres 76. As compared to a dicot root, a monocot root has [2012M] (a) many xylem bundles. (b) relatively thicker periderm.

11 86 (c) inconspicuous annual rings. (d) more abundant secondary xylem. The vascular bundles are arranged in a loose circle inside the endodermis of a monocot root. In a monocot root, more than six vascular bundles are present. It shows polyarch condition. 77. Age of a tree can be estimated by: [NEET 2013] (a) biomass (b) number of annual rings (c) diameter of its heartwood (d) its height and girth Age of a tree can be estimated by number of annual rings. Annual ring constitute alternate concentric rings of spring wood and autumn wood. 78. Lenticels are involved in: [NEET 2013] (a) Gaseous exchange (b) Food transport (c) Photosynthesis (d) Transpiration Lenticels are lens shaped openings occurs in stems of most of the woody trees. It permits the exchange of gases between the outer atmosphere and the internal tissue of the stem. 80. Which of the following statements is not true for stomatal apparatus? [NEET Kar. 2013] (a) Inner walls of guard cells are thick (b) Guard cells invariably possess chloroplasts and mitochondria (c) Guard cells are always surrounded by subsidiary cells (d) Stomata are involved in gaseous exchange Sometimes, a few epidermal cells in the vicinity of the guard cells become specialised in their shape and size and are known as subsidiary cells or accessory cells. 81. Meristematic tissue responsible for increase in girth of tree trunk is [NEET Kar. 2013] (a) Apical meristem (b) Intercalary meristem (c) Lateral meristem (d) Phellogen Lateral meristems are meristems which occur parallel to the circumference of the organs in which they develop. They undergo periclinal divisions producing secondary tissues on the outer and inner sides and increase girth of the plant organs. Examples are vascular cambium and corkcambium. : Interfascicular cambium develops from the cells of: [NEET 2013] (a) Xylem parenchyma (b) Endomermis (c) Pericycle (d) Medullary rays At the time of secondary growth interfascicular cambium is formed by parenchymatous medullary rays. Interfascicular cambium along with intrafascicular cambium (formed from cambium cells present between xylem and phloem) constitute continuous cambium ring. If cut off new cells in both directions cause secondary growth in most dicotyledonous plants.