Q.Explain the mechanism of biotic stress.

Step 1. Biotic stress is the adverse effect on a plant produced by other living organisms - viruses, bacteria, fungi, parasites, insects, weeds and competing plants - and it is also linked to human activities such as cutting trees and herbs for fuel, fodder or agricultural use.

Step 2. Because bacteria, fungi and nematodes causing biotic stress are always present as a background risk in the environment, they are described as potential biotic stresses, and the chapter recognises two specific mechanisms by which this stress operates.

Step 3. Allelopathy is the first mechanism: an organism produces one or more biochemical substances, called allelochemicals, that strongly influence the germination, growth or reproduction of other organisms; these are released from leaves after leaching onto the ground, or exuded directly from roots, and can be either beneficial (positive allelopathy) or harmful (negative allelopathy) to the organism receiving them. …

Explain biotic stress's two named mechanisms, allelopathy and pathogenicity, w …

• Describing biotic stress only in general terms (competing organisms) without naming the specific allelopathy/pathogenicity mechanisms and examples the chapter gives. …