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...

TYPES OF LEAVES: 1.Dorsiventral/Bifacial:  The leaves that are having distinct upper and lower surface are called Bifacial Leaves. They are Horizontal. Mostly in Dicots. Their Upper surface is shiny (Ventral/Adaxial) while Lower surface is dull (Dorsal/Abaxial). Stomata usually on Lower Surface. Anatomically mesophyll is differentiated into upper palisade and lower spongy Parenchyma 2.Isobilateral/Equifacial: The leaves that are having no distinct upper and lower surface are called Equifacial Leaves. They are Vertical. Mostly in Monocots and in some Dicots. Their Upper surface and Lower surface are similar. Anatomically mesophyll is not differentiated. Stomata usually on Lower Surface. SOME IMPORTANT POINTS: Floating plants has stomata on the upper surface/abaxial surface of leaf. In Submerged plants stomata are absent

  S TRUCTURE                                  Shoot Tip. The stem shoot apex produces leaf primordia that develop into leaves. Node. The site where a leaf as well as axillary buds, arise on the stem is termed a node Internode. The elongated portion of a stem between two nodes is called an internode Young stem comprises of three main regions A terminal bud which develops at the apical end of the stem, encloses a meristematic stem axis with its apical meristem Axillary buds are lateral buds that form at the leaf-stem axils (nodes) Bud will give rise to flower or branches. Leaf Scar. A scar remains on the stem where a leaf stalk (petiole) was attached. Leaf scars and buds are species-specific, and therefore, are useful for winter plant identification. Dicot stem comprises of following layers: Epidermis Cortex Stele EPIDERMIS: The epidermis consists of a single layer of cells and is the outermost layer...

Passage of water and Solute in Roots Water and ions are taken up from the soil, move radially through the cortex to endodermis to the stele.  There are two anatomical pathways of water and mineral ion uptake in roots. 1.Symplast Pathway: Water and mineral ions move across the root hair plasma membrane and immediately enter the root hair cytoplasm. They then travel cell-to-cell via plasmodesmata through the cortex, endodermis, and into the stele. The “decision” on which ions the plant takes up is made at the root hair. 2.Apoplast pathway: Water and ions passively enter the cell wall space of the cortex and diffuse to the cell wall space of the endodermis. There, the Casparian strip blocks further apoplastic movement, and the ions must be transported across the plasma lemma of the endodermal cells to enter the symplasm and move on to the stele. In this case, the “decision” on which ions the plant takes up is made at the endodermis. SUMMARY: APOPLAST TRANSPORT: The transfer of m...

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...