Plant Pathology MCQ Question and Answer | Agriculture MCQ Question

The following percentage of water absorbed by herbaceous plants is lost in transpiration 99.
Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers.
Water is necessary for plants but only a small amount of water taken up by the roots is used for growth and metabolism. The remaining 97 - 99.5% is lost by transpiration and guttation.

Bordeaux mixture and Sulphur is a protectant fungicide.
Bordeaux mixture- a combination of copper sulfate, lime, and water- is an effective fungicide and bactericide that has been used for decades to control diseases of fruit and nut trees, vine fruits, and ornamental plants.
Sulphur 80% WDG is a non-systemic fungicide that works through contact and vapor action. It's a fungicide with preventive, curative and eradicative action on various crop pathogens.

Anton Van Leeuwehoek discovered Biofilm.
A biofilm is an assemblage of surface-associated microbial cells that is enclosed in an extracellular polymeric substance matrix. Van Leeuwenhoek, using his simple microscopes, first observed microorganisms on tooth surfaces and can be credited with the discovery of microbial biofilms.
Back in the 17^th century, when Anton Von Leeuwenhoek, the inventor of the Microscope, saw microbial aggregates (now known to be Biofilms) on scrapings of plaque from his teeth. The term 'Biofilm' was coined by Bill Costerton in 1978.

The pathogen of rice blast or 'rotten neck' is Pyricularia oryzae.
Rice blast disease, which is caused by the fungus Pyricularia oryzae, inflicts serious damage to rice leaves (leaf blast) and panicles (panicle blast). Panicle blast is directly linked to rice production and quality.
The fungus reproductive structures, spores, can spread from these two sources to rice plants during the next growing season and initiate new infections.

Grain smut of sorghum is an externally seed-borne disease caused by the pathogen Sphacelotheca sorghi.
The pathogen is externally seed borne. Optimum environmental conditions for maximum infection include: temperatures between 20° and 25°C and slightly acidic soils favour the disease development.
The affected plants can be detected before the ears come out. They are shorter than healthy plants with thinner stalks and marked tillering. The sorus is covered by a thin membrane that ruptures very early, exposing the spores even as the head emerges from the sheath.

The term Parasexuality was given by Pontecarvo & Roper.
Parasexuality is referred to or being reproduction that results in the recombination of genes from different individuals but does not involve meiosis and the formation of a zygote by fertilization as in sexual reproduction.
It was first described in 1953 by the Italian geneticist Guido Pontecorvo during studies on Aspergillus nidulans, parasex describes a non-meiotic process of ploidy reduction that produces genetically diverse progeny.

'Plant Pathology' written by Agrios.
The classic textbook in plant pathology outlines how to recognize, treat, and prevent plant diseases.
It provides extensive coverage of abiotic, fungal, viral, bacterial, nematode, and other plant diseases and their associated epidemiology.
It also covers the genetics of resistance and the modern management of plant disease.

Plasmolysis is due to Exosmosis.
Plasmolysis is a typical response of plant cells exposed to hyperosmotic stress. The loss of turgor causes the violent detachment of the living protoplast from the cell wall.
As exosmosis is the movement of water molecules from within the cell to outside through a semipermeable membrane. This process ultimately causes shrinkage or plasmolysis of the cell.
The plasmolytic process is mainly driven by the vacuole. Plasmolysis is reversible (deplasmolysis) and characteristic of living plant cells.

Enzymes connected with the opening and closing of stomata are PEP carboxylase.
Phosphoenolpyruvate carboxylase is an enzyme in the family of carboxy-lyases found in plants and some bacteria that catalyzes the addition of bicarbonate (HCO₃^-) to phosphoenolpyruvate (PEP) to form the four-carbon compound oxaloacetate and inorganic phosphate.
When water evaporation is minimal, it takes in CO₂ by fixing with PEP to form oxaloacetate through PEP carboxylase and causes the opening of stomata.

Carboxin is a fungicide with apoplastic movement.
Carboxin was inhibitory to succinic dehydrogenase assayed with phenazine methosulphate plus DCIP when intact mitochondria were used as the enzyme source but not when the solubilized enzyme was used.
The main site of action of carboxin, therefore, appears to lie between succinate and coenzyme Q.
When water moves from cell to cell through the intercellular spaces or walls of the cells and hence on the outer side of the plasma membrane, is termed apoplastic movement.