Biology-Botany class 11

Botany at a Glance

  1. Tracheids are the most primitive element of xylem.
  2. Sieve tube elements are without nuclei at maturity.
  3. Companion cells are absent in phloem of pteridophytes and gymnosperms.
  4. Phloem parenchyma is absent in most of the monocots and few dicots like Ranunculus.
  5. P-protein is a constituent of sieve tube elements.
  6. Sachs (1857) classified the tissue systems into three types namely epidermal tissue system, ground tissue system and vascular tissue system.
  7. Epidermal tissue system is derived from protoderm.
  8. Mostly epidermis is uniseriate (single layered) but in Nerium, Ficus, Peperomia it is multiseriate.
  9. Endodermis acts as water dam and prevents the movement of water from the stele to the cortex. It also acts as air dam preventing the diffusion of air into vessels.
  10. Pith is mostly parenchymatous and stores water and food materials. It is large in dicot stem and monocot root but poorly developed or absent in dicot root.
  11. In some cases like sunflower stem, pericycle is heterogeneous, i.e., composed of the thick-walled and thin-walled cell, sclerenchymatous and parenchymatous, respectively.
  12. Pericycle is present in most of the roots except in roots of parasitic plants and hydrophytes.
  13. Wardlaw (1928) reported the phenomenon of heterarchy in Nymphaea chilensis.
  14. Bicollateral vascular bundles are found in families Cucurbitaceae, Solanaceae and Myrtaceae.
  15. Origin of adventitious roots is endogenous, i.e., from pericycle or cortex, thus, deep-seated.
  16. In most cases, lower leaf epidermis can be easily peeled as compared to upper epidermis because lower epidermis has more stomata.
  17. Vascular strand having numerous scattered fibrovascular bundles is atactostele (e.g., monocot stems)
  18. Dicot showing atactostele is Amaranthus.
  19. In roots, xylem is exarch or centripetal, i.e., protoxylem or first formed xylem is towards the periphery.
  20. Casparian strips are chemically lingo-suberin.
  21. Casparian strips are so called because these were discovered by Caspar (1865).
  22. Root hair forming cells are called trichoblast.
  23. In dicot stem, hypodermis is collenchyma Tous while in monocot stem, it is sclerenchymatous.
  24. In dicot stem, the pericycle is multilayered.
  25. Vascular bundles covered by sclerenchymatous sheath are found in monocot stem and such vascular bundles are called fibro-vascular bundles.
  26. Monocot leaves possess intercalary meristem.
  27. Rolling grasses are Agropyron, Ammophila, Poa, etc.
  28. In leaf, the protoxylem elements face towards the adaxial side whereas the phloem lies on the abaxial side.
  29. Cambial ring increases in diameter due to anticlinal division and radial elongation of cambial cells.
  30. Cambial cells are rectangular, thin-walled, full of protoplasm and having meristematic activity.
  31. Springwood and autumn wood of a year constitute the annual ring.
  32. The wood of commerce is heartwood (duramen).
  33. Central, older, dark coloured and resin clogged secondary xylem is heartwood.
  34. The oldest part of phloem in a dicot stem is situated just inner to the primary cortex.
  35. In an old stem, the oldest secondary xylem is found outside primary xylem.
  36. Tylosis always passes through the pit.
  37. Patua of Hibiscus sabdarifa is secondary phloem.
  38. Austrobaileya is an angiosperm without companion cells.
  39. The time gap between two successive leaf primordial is called plastochron.
  40. Anomalous or abnormal secondary growth occurs in some monocot stems e.g., Yucca, Dracaena, Aloe, Sansevieria, Agave, etc.
  41. Carolus Linnaeus is called the father of Taxonomy while Henery Santapau is considered to be the father of Indian Taxonomy.
  42. Magnoliaceae in woody plants and Ranunculaceae (in herbaceous plants) are considered to be most primitive families according to John Hutchinson.
  43. The symmetry of flower is represented by both the floral diagram and floral formula.
  44. Family Poaceae is the most advanced family of monocotyledons.
  45. Ovary with parietal placentation is always unilocular.
  46. Silky hairs in maize cob are long styles.
  47. Aspidistra in family Liliaceae is having tetramerous flower (not trimerous)
  48. The taxonomy includes identification, nomenclature and classification. Identification is the first act in taxonomy.
  49. Term systematics (GK. Systema = order or sequence) was given by Linnaeus (1751) while the term taxonomy (Gk. Taxis = arrangement; nomos = law) was given by A. P. de Candolle (1813). Often term classification, systematics and taxonomy are used interchangeably but Simpson (1961) differentiated these terms. According to him, systematics is the study of the diversity of organisms and all their comparative and evolutionary relationships based on comparative anatomy, ecology, physiology and biochemistry. Classification comes under systematics and is related to ordering organisms into groups. Taxonomy is related to the study of principles and procedure of classification.
  50. Linnaeus is called the father of taxonomy and modern botany. Linnaeus laid the foundation of modern classification in a book entitled “Systems nature”.
  51. Species is the smallest/basic/lowest/unit of classification and consists of the natural population. Members of a species can interbreed freely and produce fertile offspring in natural condition. One species is reproductively isolated from other such groups.
  52. The taxonomic hierarchy has seven categories, called obligate categories viz. kingdom, phylum (for animals) or division (for plants), class, order, family, genus and species.
  53. Species is the basic or lowest unit of classification while the kingdom is the highest category.
  54. As we go down in the taxonomic hierarchy from kingdom to species, the number of organisms decreases in categories while the number of similar characters increases.
  55. The tribe is placed between family and genus.
  56. Broadly there are three systems of biological classification-artificial, natural and phylogenetic.
  57. Artificial system is based on one or a few characters e.g. classification given by Aristotle, Linnaeus, etc.
  58. The classification given by Linnaeus is called sexual system of classification. It is based on the morphology of floral parts, number and arrangement of stamen and carpel.
  59. In a natural system, organisms are classified on the basis of a large number of characters showing their natural affinities e.g. Bentham and Hooker’s system of classification.
  60. Bentham and Hooker’s system of classification was given in the book ‘Genera Plantarum’. It is called practical system of classification and widely followed in former British colonies.
  61. Phylogenetic system (or cladistics) is based on the evolutionary and genetic relationship among the organisms. Organisms are classified according to historical order in which the evolutionary branch arose e.g. classification is given by Engler and Prantl, Hutchinson, Takhtajan etc.
  62. To emphasise the role of phylogeny in classification, Parkin gave the statement “Taxonomy without phylogeny may be linked to bones without flesh and was supported by Takhtajan.
  63. In Biosystematics (or new systematics) classification of an organism is based on their evolutionary history establishing their phylogeny on the basis of knowledge obtained from as many branches as possible, e.g., morphology, anatomy, biochemistry, chromosome number and other cytological features and experimental taxonomy. The term new systematics or biosystematics was given by Sir Julian Huxley (1940).
  64. Two kingdom classification was given by Linnaeus. He divided living the world into two kingdoms :
    (i) kingdom Plantae and
    (ii) kingdom Animalia.
  65. Three kingdom classification was given by Ernst Haeckel. He separated unicellular plants and animal into a separate kingdom, ‘kingdom Protista’.
  66. Four kingdom classification was given by Copeland and Stanier (1956). A new kingdom Monera was created to accommodate prokaryotes such as bacteria, blue-green algae, etc. The four kingdoms are Monera (or Mycota), Protista (or Protoctista), Metaphyta and Metazoa.
  67. Five kingdom classification was given by Robert H. Whittaker in 1969 on the basis of complexity of cell (prokaryotic/ eukaryotic), the complexity of the organism (unicellular/ multicellular), mode of nutrition (autotrophic/ heterotrophic) and major ecological role (producer/ consumer/ decomposer).
  68. Earlier fungi were included in kingdom Plantae. Whittaker separated them and elevated ranking of fungi as a kingdom.
  69. Biochemically monerans are the most diversified group while morphologically animals are the most diversified group.
  70. Prokaryotes belong to kingdom Monera.
  71. Unicellular eukaryotes were kept in kingdom Protista.
  72. Eukaryotes have been assigned to four of the five kingdoms.
  73. Monera includes prokaryotic organisms like bacteria, blue-green algae (Cyanobacteria), mycoplasma, archaebacteria, rickettsiae, chlamydiae, etc.
  74. Bacteria were discovered by Antony von Leeuwenhoek of Holland from stored rainwater and tartar scraped from the teeth. He called them dierkene/ beasties/ tiny animalcule.
  75. Term bacteria was given by Ehrenberg.
  76. Robert Koch is called the father of Bacteriology.
  77. Smallest living cells with cell wall capable of growth and division are Bacteria (Dialister pneumosintes).
  78. The smallest free-living organism is Mycoplasma (M.gallisepticum).
  79. The cell wall of monerans such as bacteria and cyanobacteria is made up of polymer called Peptidoglycan/mucopeptide/glycopeptide or murein.
  80. Murein is a derivative of sugar having amino group N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM).
  81. The cell wall is rigid in Gram-positive bacteria due to the presence of high proportion of peptidoglycan. Cell wall provides shape to a bacterium and is responsible for the antigenic activity.
  82. Plasmids are found in bacteria. These are present in addition to main DNA. These are small double-stranded circular DNA which replicates independently of the main DNA. Some of the genes such as genes for antibiotic resistance (R factor plasmid) genes for fertility (F factor plasmid), genes for production of toxin colicin (col plasmid), etc. are present on these plasmids. Those plasmids which can reversibly integrate with main DNA in bacteria are called episome.
  83. Membrane-bound cellular organelles are absent in bacteria.
  84. Bacteria are the most abundant organisms present on earth because their rate of multiplication is very fast.
  85. Most common method of their reproduction is binary fission.
  86. Some bacteria form thick-walled resistant spore called endospore, e.g., Clostridium, Bacillus Endospore survives pasteurisation.
  87. Azotobactor and Bacillus polymyxa are free-living non-symbiotic aerobic nitrogen-fixing bacteria.
  88. Clostridium is free-living anaerobic, non-symbiotic nitrogen-fixing bacterium.
  89. Frankia is a symbiotic non-leguminous nitrogen-fixing bacterium. It forms root nodules in non-leguminous plants.
  90. Rhizobium is symbiotic nitrogen-fixing bacterium and forms root nodules in leguminous plants.
  91. In cheese, manufacture microorganisms are important for souring and ripening process.
  92. Agrobacterium is used extensively in genetic engineering as the vector for the transfer of genes in plants. A. tumefaciens and A. rhizogenes are two species used for this purpose.
  93. Genetically modified Pseudomonas putida bacterium was developed by an Indian-born, U.S. Scientist, Prof. A.M. Chakraborty. This bacterium has genes for degrading various types of hydrocarbons. It is used to clear oil spill to spread on the sea surface during accidents of oil tankers.
  94. E. coli bacterium lives as a commensal in the human large intestine and synthesises vitamin K and.
  95. E. coli is used as an indicator of water quality. Drinking water should not contain more than 2 to 3 bacteria per litre.
  96. Penicillin inhibits bacterial multiplication because it checks cell wall synthesis.
  97. Citrus canker is caused by Xanthomonas citri.
  98. Crown gall of fruit trees is caused by Agrobacterium tumefaciens.
  99. Most disease-causing bacteria are Gram-positive.
  100. In cyanobacteria, photosynthesis is oxygenic i.e. they evolve oxygen during photosynthesis. These were the first oxygen evolving organisms on earth and converted primitive reducing atmosphere into the oxidizing environment