Plant Science Resource

Plant Galls : Plant galls are external expression of mysterious interaction between two biological entities namely the plant and insect. The gall inducer, which are phytophagous parasites are dependent on the plant tissues not only to feed on, but also for an ideal niche to live in during a short duration of their life-cycle.   During the feeding or ovipositing efforts of the animal parasites on the plant organs, a series of action-reaction system is established between the parasites and their host plants. A compromise is reached at the end of the processes and a structure called “Gall” is produced by the plant organs.   The gall thus produced provides quality nutrition as well as safe domain to the gall-inducers and at the same time, the plants are able to localize them in space and time, thus the gall-inciting agent is physically and physiologically isolated and is driven to extreme specialization with respect to its various biological activities.   Insect-induced plant galls

Parasexual cycle                                  Earlier , it was believed that genetic recombination can only be achieved by sexual reproduction but studies on bacteria have shown that it is also possible through alternative mechanism .Such an alternative mechanism was observed for the first time by Pontecorvo & Raper (1952) seen in Aapergillus nidulans . They observed that in this specialized reproductive mechanism, plasmogamy , karyogamy and meiosis do take place but not at specified time or specified points in the life cycle of the fungus .They considered the group as Deuteromycetes or fungi imperfecti and the specialized cycle of reproduction as “Parasexual Cycle “ Mechanism of parasexual cycle: According to pontecorvo (1958) parasexual cycle in Aspergillus nidulans involves the following step ----- (a) Formation of heterokryotic mycelium: heterokryotic mycelium is obligatory for parasexual cycle. In Deuteromycetes , heterokaryotic mycelium is formed in several ways.

Mushrooms also are living organism and belong to a group known as  “Fungi”. They are  the members of  higher fungi, belonging to the class Ascomycetes and Basidiomycetes. Biologically mushrooms are very much important. The biological value of mushroom includes nutritive value, medicinal value and the efficiency in digestion of other substances.The food value of mushrooms are as follows-                                                                       1) Protein: Mushrooms are richest source of vegetable protein. The protein content varies from 1.1 to 4.9% in common cultivatable mushroom. All the essential amino acids including lysine are present  in much higher  amount than even egg. Among the mushroom aminoacid 25 to 40% occurs free, whereas the remaining in the form of  polypeptide, unusual amino acid and related nitrogenous compound. The amino aciods are- methionine sulphoxide, alanine, cysteic acid, hydroxyl lysine, amino-adipic acid, amino butyric acid, pipecolic acid, ph

  Different modes of nutrition in fungi                      The fungi are chlorophyll less organisms which cannot synthesize their own food unlike green plants. They are so simple in structure that they cannot obtain inorganic food directly from the soil and therefare , they are always dependent for their food on some dead orgainic materials or living beings. The different modes of nutrition in fungi are as follows---- 1. Parasitic mode: Fungi, which obtain food from living organisms are called parasitic fungi. The parasitic fungi absorbe their food material from the living tissue of host. They are quite harmful to their host and cause many serious diseases. Parasitic fungi may be ectoparasite i.e., grow out side the plant body (eg. Erysiphe ); or may be endoparasite i.e., grow inside the plant body (eg. Phytophthora ) parasitic fungi are farther classified as----- (a) Obligate parasite: some fungi obtain their food entirely from the living protoplasm of the host and maintain t

  Fungi are  nucleated, spore bearing, achlorophyllous, heterotrphic (saprophytic, parasitic or hyper parasitic) ,eukaryotic organisms. The fungi are related to both the useful and harmful activities to which society, biosphere and modern biology are directly concerned.Therefore economically fungi are very important biological group.   Beneficial effects of Fungi in society: 1. Edible fungi : Fructification of certain species of Amanita, Boletus, Agaricus, Pleurotus, Auricularia, Phallus etc are edible as mushroom, which contain a huge nutritive value. The food value   of button mushroom Agaricus bisporus is as follows-   Composition Percentage 1.       Water 81% 2.       Solids 9% 3.       Carbohydrates 2.4% 4.       Protein (N X 6.25) 3.3% 5.       Fat 0.4% 6.       Ash 0.4%   It also contain several essential amino ac