Seed Size
Seed size is an influential trait that impacts a number of functional traits, including offspring fitness and reproductive success. Physical factors (competition, predation and optimal dormancy depth) as well as biological ones such as seed-seedling competition, water availability and seedling growth rate all influence its size.
Seed morphological parameters such as length and width are crucial indicators of seed quality. Measurement methods vary, from manual counting by hand or digital image-based tools to digital image analysis tools; typically ten seeds from each sample will be measured, although in cases with higher intraspecies variability this number may need to increase accordingly.
Standard seed measurement methods use a microscope ruler or micrometer. These devices allow us to quickly take measurements using either “box” measurements, which take simultaneously parallel length and width measurements of seeds, or two separate linear measurements that record length and width measurements perpendicular to one another, or two linear measurements when dealing with irregular shapes like those caused by inflation, or those that do not lie flat enough for measurement.
Seed Percentage
A bag of wildflower seeds may weigh in total but that does not tell the full story; some of that weight comes from inert material such as broken seeds, chaff and soil particles that do not contribute anything beneficial for plant growth and add unnecessary cost.
PLS measures how much seed can actually be planted. PLS is calculated using both purity and germination percentages multiplied together and divided by 100.
Typically speaking, higher PLS percentages are better; however, certain species naturally exhibit lower rates. Also keep in mind that the germination percentages listed on seed analysis tags reflect ideal laboratory conditions and may not reflect actual field performance; if seed has a germination rate below 50% it might be wise to switch out mixes as weak seedlings often get eaten up by pests and animals.
