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AUXINS:  Darwin performed some experiments on canary grass. In his experiments, when the coleoptile of grass was unilaterally illuminated, it curved towards the source of light. The experiments done by him confirms some interations  between the tip and light and light resulting in curvature of tip.     Went removed the tip of avena coleoptile and placed it on agar-agar block for a measured length of time and it produces a positive curvature. He named this substance as Auxin. Isolation of Auxin Kosland Hargen-Smith isolated Auxin-A from human urine. Kogl, Erxlaben and Hargen- smith isolated Auxin-B from corn germ oil. It was chemically identified as Indole-3 Acetic Acid(IAA). Biosynthesis of Auxins Thimann 1935 observed the fungus Rhizopus Suinus can convert the amino acid Tryptophan into IAA. Transport: Auxins occurs in the meristems. It is transported polarly and movement is basipetal. Physiological effects: Induces cell elongation...

Growth in plants: Growth is irreversible and permenant increase in size of cell or tissue or organ or entire plant body. It is always accompained by metabolic associated reactions. Growth in plants is indeterminate and grows till death due to the activity of meristems in plants. Growth can be measured by increase in protoplasmic content, fresh weight, dry weight, length, area, volume and number of cells.  Phases of growth: In plants growtg and development each cell undergoes three phases. 1. Meristematic phase:       In this phase meristematic cells divides continuously. The cells are active and this phase is also called as Cell-division Phase. 2. Elongation phase:        The cells which are formed in meristematic phase becomes enlarged in thier size and forms vacoules at the centre of the cell. 3. Maturation phase:          The cells are matured and differentiated into tissues to perform spe...

POLLINATION: In a simple words pollination us the transfer of pollen grains from anther lobe to the stigma of gyneocium. Types of pollination: Two types of pollination has been observed. They are. 1. Cleistogamy 2. Chasmogamy Cleistogamy: Pollination that occurs in unopened flowers is called Cleistogamy. Ex. Sereteocarpus. Chasmogamy: Pollination that occurs in opened flowers is called Chasmogamy. There are two types in this type. They are. 1. Self pollination or Autogamy. 2. Cross pollination. 1.Autogamy or Self Pollination.  The transfer of pollen grains from the anther to the stigma of same flower is called Autogamy or Self Pollination. 2. Cross-Pollination.  Teansfer of pollen grains from anther to the stigma of another flower is known as cross pollination. It is again of two types. Geitonogamy.  xenogamy. Geitonogamy:  It is the transfer of pollen grains from anther to the stigma of another flower of sa...

Cyanobacteria General characters: Also called as Blue-green algae. Found in water and other wet places. These are oxygenic photosynthetic, prokaryotic and gram negative bacteria. The outer layer of cell wall is made of lipo-polysaccharides and inner layer is having peptidoglycon. Ribosomes, thylakoids and phycobilosomes are present in cytoplasm. Ribosomes are 70s type, thylakoids contains phycobilosomes which has photosynthetic pigments like phycocyanin, phycoerythrin and small amount of protein. Reserve food material is cyanophycin granules, starch, glycogen, phosphate granules. Gas filled vacoules helps the bacteria to float on the surface of water.  Vegetative reproduction is by fission, fragmentation and by locomotion harmagonia. Asexual reproduction is byformation of akinites, endospores, exospores and nanocytes. Thallus organisation in cyanobacteria: Thallus organisation in the sense no differntiation of organism into different parts. It is in  thr...

Lichens: The symbiotic assosiation between fungi and algae resulting in a plant body is called lichens. Plant body of lichen thallus is irregular and made up of algal component i.e. phycobiont and fungal component i,e. Mycobiont. Differnt forms of lichens: 1. Crustose lichen:     These are flat, thin, crust like thallus appeared partly or completely embedded into the substratum.  Ex. Rhizocarpa graphis. 2. Foliase lichens:    These are flat, leaf like lobed thallus attach to the substratum with the help of rhizoids.  Ex. Permeria. 3. Fruticose lichens:     These are brush like hanging cylindrical or spherical shape. Attached to substratum with the help of basal mucilage disk.      Ex. Cladonia. Internal morphology of lichen thallus:    It shows mainly four zones. They are:            1. Upper cortical zone            2. Algal zo...

Classification by Aristotle: Aristotle was the earliest to attempt a scientific basis for classification. He classified plants and animals as two groups He classify plants into trees, shurbs and herbs. He divided animals in two groups , those who have red blood  and those do not contain red blood. Classification by Linnaeus: Linnaeus classified as Two Kingdoms, i.e Plantae and Animalia. But this two kingdom classification found inadequate because a large number of organism did not fall in either category. There was no differentiation between unicellular and multi cellular, autotrophic and heterotrophic, difference in their cell wall composition, so a need was felt to classify them in an appropriate manner. So Whittaker classified it again and it is widely used now a days. Whittakers classification: R.H.Whittaker proposed a Five kingdom classification in the year 1969. They are Monera Protista Fungi Plantae Animalia The main criteria for cla...

Normally secondary growth is absent in monocots. Monocots live for a short period of time and complete its life cycle. Example:jawar, maize, rice etc., But Dracena shows abnormal secondary growth being a monocot stem. Dracena belongs to Lilliaceae family. Formation of Periderm: During secondary growth few peripheral cells of general cortex becomes active and forms Meristem. This acts as Cork cambium or Phellogen. This cork cambium cuts off Cork tissue or Phellem towards outside and secondary cortex or phelloderm towards inside. By this periderm is formed. Formation of cambium: The inner peripheral cells of general cortex becomes meristemetic and forms cambium. Cambium forms parenchyma cells and xylem elements in its inner side. After a short period of time activity changes. Phloem is formed in such a way that phloem is surrounded by xylem. This type of vascular bundles are called Amphiphloic type. In which phloem is surrounded by xylem. ...