Factors affecting seed and seedling vigor

1. Genetic control or genotypic effect:

• The competence of genotype in a particular environment determines seed vigor.
• The influence of genetic control of seedling vigor is found in hybrid and polyploidy plants over inbred and diploid of the same species.
• For example, seeds of barley hybrids have been found to germinate faster, grow faster and exhibit a higher respiration rate than either parent (McDaniel, R.G. 1969)

2. Seed size and density:

• The superior performance of graded large seeds of jute in respect to field emergence, better crop stand at harvest and fiber yield than the small size seeds have been reported by Ghos and Sen.(1981)
• Similarly, Kalakannavar et al (1989) reported that large wheat seeds had increased germination percentage, rate of field emergence as well as the root length, dry weight and vigor index of the seedlings.

3. Seed maturity:

• Fully mature seeds have the potential to complete physical and physiological development needed for maximum expression of vigor.
• Seeds of most crop plants that can be dried, stored at low moisture and cool storage condition (orthodox seeds) can maintain seed vigor for a long time.

4. Timing of harvest:

• In plants with determinate flowering, seed maturity is relatively uniform and the seeds mature at the same time but in case of indeterminate flower (sugarbeet, carrot) harvest at any time, yield seeds with varying stages of maturity and these seeds have low germination and low seed vigor.

5. Temperature and moisture availability during seed development:

• Temperature and soil moisture availability during seed development of most of the crop species affects the seed size, yield, germination as well as seed vigor, seedling vigor and subsequent yield.
• Water availability during seed development may influence seed vigor indirectly through its influence on the chemical composition of the mature seed.
• For example, N content (protein) of cereal seed generally decrease as the amount of water supplied during the vegetative development of the parent plant increases.

6. Soil fertility during seed development:

• The fertility of soil in which the plant grows influences the chemical composition of the developing seeds and consequently its metabolism and vigor during germination.
• It appears that N and P2O5 availability can influence seed development and seedling vigor, but their effect varies among species and is highly dependent on the stage of growth and development and environmental conditions.

7. Mechanical damage:

• The mechanical damaged (cracked and broken seeds) may appear normal but exhibit low vigor than undamaged ones.
• It is due to the physiological deterioration triggered by impact or it may be purely physical damage as a result of cryptic, microscopic breaks at crucial locations within the seed.

8. Attack of microorganisms:

• Infestation by microorganisms cause deterioration of seeds in storage and may further reduce seedling vigor by attacking the germinating seedlings.

9. Chilling injury during imbibition:

• Seeds of many warm season species are especially susceptible to low temperature injury during moisture imbibition and early seedling growth.
• For example, imbibition of moisture by soybean seed at 50C was reported to cause reduction in seedling survival, dry matter accumulation and seedling height (Obendorf, R.L. and P.R. Hobbs, 1970).