PLANT DEFENCE THROUGH SEEDS
The reproduction code of a flowering plant, that can develop into another same type of plant. Other definitions of seeds also used in literature such as (1) The grains or ripened ovules of plants that are the source of are said to be used for sowing. (2) The fertilized ovule, which is ripened finally, of a flowering plant having an embryo in it and capable of germination to produce a new plant effectively.
3)A propagative structure of a plant and is like spore or a small dry fruity structure. Survival of seeds is very necessary for the survival of any type of plant species that may be a tree, a horticultural plant, a vegetable or an ornamental type of plants, but in common the environmental factors that control seed survival at a landscape level always considered importance blank. The most common factors soil moisture, soil texture, soil chemical biological and physical properties, vegetation cover, soil type, and soil pathogens, etc. Physiological seed dormancy provides a plant with physical and chemical defenses continuously, depending on soil pathogen which varies with varying environment.
Defense of seed for natural situations
Plant defense through seed defense recognizes the natural enemies that seeds encounter an able the plant against these factors by so-called having natural phytotoxic responses. A seed has disease resistance in their genes in coding a decoding series of resistive genes inherited from parents during reproduction processes. With varying environmental condition and adaptive measures plant seed endorses a new set of changes in its genetical makeup through the adaptive process. Digestive enzyme inhibitors are proteins that block the normal digestion and absorption of nutrients by microorganisms. Alpha-amylase inhibitors are proteins commonly found in legumes that bind to amylase enzymes and inhibit starch digestion in plants. Lectins are non-enzymatic proteins and glycoproteins that bind to carbohydrates and exhibit a wide range of functions including disruption of digestion in insects and agglutination of blood cells invertebrates. Ricin is a powerful toxin produced in castor beans. It combines a lectin molecule with an N-glycoside hydrolase that enters animal cells and inhibits protein synthesis. Ricin is a highly potent toxin, having an average lethal dose of only 0.2 milligrams in humans. Physical defenses of seeds are most apparent in species with ‘hard seeds’, a term synonymous with physical dormancy, where the seed is impermeable to water until germination commences. Physical dormancy has already been suggested to play a defensive role, as rodents that rely on olfactory cues cannot detect buried seeds that remain impermeable. Here we suggest that physical dormancy also provides an effective barrier against microbial access to nutrient-rich seed contents.
Physical way of defense
Physical defenses may also extend to some seeds with physiological dormancy, as seed-enclosing structures may need to soften before the radicle can emerge. Permeability of these structures may therefore also be sufficiently restrictive to prevent microbial access to the seed embryo. Seeds contain a diversity of secondary chemicals, often at concentrations much higher than elsewhere in the plant. Synthesis of chemical defenses is costly and potentially equivalent to the investment in seed physical defenses. In most cases, the relative effectiveness of chemical defenses against different classes of seed predators and pathogens has not been assessed. Those considered to be effective against microbial infection in the soil include phenolic compounds, anti-fungal proteins, and alkaloids.
Seed coat prevention
An impermeable seed coat prevents microbial access to seed reserves, then we predict that seeds with physical dormancy will allocate little to chemical defense. Endophytic fungi will also be absent from the interior of these seeds or should be limited to those that colonize during seed development. However, physically dormant seeds may benefit from beneficial fungi and bacteria arrayed on the exterior of the seed. In the absence of chemical defenses, we predict that physically dormant seeds must rely on rapid germination to escape soil pathogens. Along these lines, radicle emergence is often observed to occur quickly after water-impermeable seed coats are compromised. We predict that seeds with physiological dormancy will vary in their investment in chemical versus physical defenses depending on seed persistence and habitat type. In habitats where pathogen pressure is relatively low (e.g. arid ecosystems or well-drained, temperate agricultural fields) physical defenses may be enough to ensure long-term seed persistence. For these species, we predict that (I) seeds will be less permeable to bacteria and fungi than species that rely on chemical defenses and (ii) that microbial and chemical defenses, if present, will be arrayed on the exterior of the seed. In habitats where pathogen pressure is high, then physical defenses alone may be insufficient to prevent pathogen infection, and seed persistence is positively correlated with chemical defense….