Botany Studies

Discovery of Phytochrome Phytochrome is a blue-green pigment involved in the perception of photoperiodic stimuli controlling flowering and other growth phenomenon such as seed germination, etc. The discovery of phytochrome was made during studies by Borthwick, Hendricks and their colleagues. They revealed that a pigment system is involved in the germination of lettuce (Lactuca sativa) seeds. They found that germination of these seeds is stimulated by red light (660 nm). They found that far-red light (730 nm), given immediately after a red-light exposure, inhibited germination, and when the seeds were again treated with red light, germination was promoted. They suggested that there is a reversible pigment system in lettuce seeds. The last light treatment determines the response of the seeds. Thus, the action spectrum of lettuce seeds is similar to that of photoperiodism. Chemistry & Physiology of Phytochrome The phytochrome occurs universally among green plants and was isolated from...

  The members of this genus are commonly called   mushrooms.  Mushrooms grow on soil. They are abundantly found on soil with decry plant material and moisture. The specie   ,4garietts campsites  is very common. This species is edible. It is cult hated for commercial purposes. General structure The mature plant body is composed of two parts: vegetative mycelium and sporophores Vegetative mycelium:  It is underground part of the mycelium.It is composed of simple filamentous hyphae.The cells of the mycelium are uninucleate at first.Later two hyphae fuse with each other.The mycelium thus becomes dikaryotic.The mycelium develops rhizomorphs.Sporophores develop on rhizomorphs. Sporophores:  Mature fruiting body is called  sporophore.  It is pres:nt above the ground. Sporophore is umbrella like. It ha f stalk or  stipe.  A cup like  pileus  is present at the tip of stipe. Both stipes and pileus are formed of compact mass of hypha...

  (a) Role of fungi in Agriculture or crop production Decomposition and humus formation:  Fungi decompose the dead animals and plants. Fungi change them into humus. rums is decomposed organic matter. It plays an important role in germination of plant. It provides important nutrient to plants. Humus also holds the soil particles. Thus it reduces the chance of soil erosion. Humus also increases the water holding capacity of soil. 9iological succession:  Fungi are important part of lichens. Lichens play an important role in biological succession They make barren land suitable for cultivation. Biological nitrogen fixation:  Lichens are also involved in biological nitrogen fixation. They fix the atmospheric nitrogen to form nitrates. These nitrates are absorbed by the plants. Some fungi are also involved in free biological nitrogen fixation. Role of mycorrhizae:  Mycorrhizae is an association between fungi and roots of higher plants. It has great survival value for p...

RUSTS Causative agent:  Puccinia graminh ( Basidiomycota)   Affected plants:  Wheat, barberry   Symptoms: Reddish streaks (pustules) appear on the stems and other parts of wheat. These streaks may affect most of the plant. They give rusted appearance to whole of the plant. As the season advance-, the streaks change from red to bl wk. The crop gives burnt dried look. The barberry plant shows the presence of small circular yellow s jots on the tipper surface of leaves. They are changed into flask-shaped  pycnidia.  Pycnidia contain hyphae and pycnichospores. The leaf bears cup-like structures on the ventral surface. These are called cluster-cups or aecidia.  Aecidia  contain aecidiospores. Host parasite relationship:  Uredospores and aecidiospores genninate on wheat. They produce germ-tubes. Germ lute enters thro ‘eh the stomata. It develops into intercellular mycelium. This mycelium develops haustoria. Environmental Relationship:  Moderat...

General characters:The intimate symbiotic association of fungi and algae is called lichens.Algae get protection and get moisture from fungus.Fungi get nutrition from the algae.The food substances diffuse from algae to fungi.The algae of lichens mostly belong to Chlorophyta and cyanobacteria. Distribution:  Lichens have worldwide distribution. The form major part of vegetation in Polar Regions. They can withstand extreme temperatures. Classification:  Lichens are classified according to algal components. There are two groups of lichens: Ascolichens: In  this case, lichens belong to ascomycota. Majority of the lichens belongs  to this group. It is further divided nto two groups on the basis of fruiting bodies. These groups are: Gymnocarpeae and pyrenocarpea. Basidiolichens:  In  this case, lichens belong to basiodmyrota. 4. Vegetative body: Lichens have thallus body. The thdli have diffi rent shapes and colours. But most of them are bluish green or grayish...

  General structure Physcia is foliose lichen. Physcia is divided into four regions internally. These regions are: 1. Upper cortex: It is present  at the upper regions. It is composed of closely packed hyphae. Spaces are absent between them. if spaces are present, they are filled by gelatinous material. The upper surface may be smooth or it has hair like structures. These hairs are formed by scattered hyphae above the cortex. Algal layer or gonidal region:  It is present below ti e upper cortex It contains algal components. Loose hyphae are present between the algal cells. Medulla:  A wide region of loosely arranged hyphae is present below the algal region. It is called medulla. It forms the major part of the thallus. Lower cortex or hypothallus:  It is present below the medulla. It is a narrow layer of compactly arranged hyphae. If the algal components are scattered irregularly among thz fungal hyphae. Then the thallus is called  homoiomerous.  If the...

  Occurrence of bryophytes Bryophytes are terrestrial plants. They mostly grow in moist and cold habitats. Some species can grow in dry places. But they depend on moisture for the reproductive stage. Bryophytes have world wide in distribution. They are found in tropical, temperate, subarctic and arctic regions. General structure Bryophytes show alternation of generation. Gametophyte The dominant generation in bryophyte is gametophyte. The vegetative plant body is a gametophyte. It has smaller size. Plant body:  The plants are multicellular. They have simple thallus. Some may be differentiated into simple leaves and stem. Vascular tissues (xylem and phloem) are absent. Roots are absent. Rhizoid performs the function of water absorption and fixing the plant to the soil. Rhizoid may be unicellular or multicellular. Reproductive organs:  Gametangia are multicellular structures. Male gametangia is antheridia and female is archegonia. Gametangia have a jacket of sterile cells. ...