Seed vigor and its role in seedling establishment.

• Binita Neupane

Seed vigour is defined as the sum total of those properties of seed which determine the potential level of performance and activity of non dormant seed or seed lots during germination and seedling emergence.

Seed vigor is not a single measurable property, but a concept associated with aspects of seed performance that includes:- rate and uniformity of seed germination and seedling growth, emergence ability of seed under unfavourable environmental conditions and performance after storage, particularly the retention  of ability to germinate.

A key component of the performance of crop seed is the complex trait of seed vigor. Crop yield and resource use efficiency depend on sucessful plant establishment in the field  and it is the seed vigor , that defines seeds ability to germinate and establish seedlings rapidly, uniformly and robustly across diverse environment conditions.

Seed vigour is highly complex. At biochemical level, it involves energy and biosynthetic metabolism, coordination of cellular activities and transportation and utilization of reverse foods. At the level of germination, it involves speed and totality of germination, pushing power of seedling, range of stress conditions under which germination will occur and disease resistance.

The vigorous seed have potential to germinate rapidly and uniformly and emerged seedlings are able to grow vigorously under general and relatively adverse field condition.

It has been noticed that seed lots of similar germination percentage gave varying results in regards to field stand. A germination test is inadequate as far as prediction of plant stand establishment is concerned.

This is primarily due to the fact that the germination test is carried out in seed testing laboratory under very favourable artificial conditions, which are seldom available in the field.

Under laboratory conditions the weekest seed can also germinate since it receives favourable moisture , temperature and substrate , which is not loaded with microorganisms, herbicides , fertilizer , fungicide or systemic insecticide. Seed lots of equal quality will produce differential response in field emergence.

Vigour test could reliably predict stand producing potential of seed lots in the field condition. The ultimate proof of any vigour test is its reliability in predicting field stands under a variety of field conditions.
A seed is said to be vigorous , if seed has good:-speed of germination , uniformity of germination and plant development under non uniform conditions, ability to emerge through crusted soil , germination and seedling emergence from cold , wet , pathogen infested soil , normal seedling morphological development , and storability under optimum or adverse conditions.

If we used the low vigour seed, then stand of seed bearing plant may be reduced, there will be delayed and reduced emergence of seedlings , plants will be dwarf with thin stems, number of nodes may be reduced ,there may be delayed maturity of the crop.

Seed vigor can be affected by number of factors like genotypic effect, seed size and density , seed maturity, timing of harvest, temperature and moisture availability during seed development , soil fertility during seed development , mechanical damage,  attack of micro organisms , chilling injury during inhibition etc.

Seed vigor has potential to significantly elevate crop resilience to biotic and abiotic stresses.

That is important for crop yields enhancement  and other enterprises that involves seeds like plant breeding, research and education, and germplasm collection. In sum up, seed vigor has very important role in seedling establishment.

(Author is Bsc Agriculture student at IAAS, TU)