TGT Science and PGT Biology Exams study material

The vertical section of a dorsiventral leaf through the lamina shows three main parts, namely, epidermis, mesophyll and vascular system . The epidermis which covers both the upper surface (adaxial epidermis) and lower surface (abaxial epidermis) of the leaf has a conspicuous cuticle.  The upper epidermis has thick cuticle than lower epidermis, this thick cuticle helps to reflect away excess sunlight. The abaxial epidermis generally bears more stomata than the adaxial epidermis. The latter may even lack stomata.  Mesophyll: The tissue between the upper and the lower epidermis other than veins is called the mesophyll.  Mesophyll, which possesses chloroplasts and carry out photosynthesis, is made up of parenchyma. It has two types of cells – the palisade parenchyma and the spongy parenchyma.  The adaxially placed palisade parenchyma is made up of elongated cells, which are arranged vertically and parallel to each other. They contain discoid chloropla...

STRUCTURE OF ROOT The overall structure of the root comprises of, the zones of division, elongation, and maturation The root is organised into three main regions Region of Division Region of Elongation Region of Maturation 1.Zone of Division (RAM): Apical meristems are the sites of primary growth. Apical meristems are zones of active cell division. Comprises of a zone of slow division: Quiescent Centre. It is subterminal in position. Protected by a Root cap, In the Root cap a specialized region called as Columella sense gravity (Gravisensing) due to large amount of amyloplast . Amyloplast of columella also do refer to as Statoliths meaning static rock and statolith containing cells are called as Staocytes. It generates cells of both the root cap and the root. It produces the protoderm, ground meristem, and procambium , which are active in the so-called zone of division. Meristemoids: The are Small superficial cluster of cells that give rise to trichomes and Stomata. 2.Zone of Elonga...

PARTS OF EMBRYO:  A seed comprises of an Embryo and Cotyledon. An Embryo comprises of Radicle, Plumule and Hypocotyl. Plumule is the Embryonic stem. Radicle is the Embryonic root. Plant Root System: There are two types of Root System on the basis of their morphology and development: 1. FIBROUS Roots 2. TAP roots. In Tap root there is a main primary root from where lateral roots arises. In Fibrous root system several main roots form a bunch. Basics of Root development: Upon seed germination Radicle forms embryonic root that further form main primary root of the plant called as  Tap Root . EXAMPLES: Most of Dicot Plants. But in Monocots there were several roots but only one radicle so how roots develop? In Monocots several roots arise just above radicle called as  Fibrous Roots. In Monocots  primary root is short lived and replaced by large number of roots Another type of roots are  Adventitious roots : Roots that develop from leaves and Stem are called as  A...

  What is Pollination? The process of transfer of pollen grains from anther to the stigma of flower is called as Pollination. Types of Pollination 1.Self Pollination/ Autogamy: The transfer of pollen grains from anther to stigma of same flower is called as Self Pollination. Homogamy is that condition in which anther and stigma mature at same time that promotes self-pollination In some plants the anthers bend toward stigma for pollination, carpel curls to receive pollen and in some cases movement of sepals and petals bring anther and stigma together in a same flower. CLEISTOGAMY:  The bisexual flowers that do not open are cleistogamous flowers. Pollination in cleistogamous flowers is called as cleistogamy.  They are very small and not coloured.  Examples: Viola, Oxalis, Commelina benghalensis, Drosera. 2. Geitonogamy: The transfer of pollen grains from anther to stigma of flower on same plant or genetically similar plant is called as  Geitonogamy. 3.Cross Pollina...