You will always find the letters N.K.P. (in South Africa) on the container in which you buy your fertilizer. N (nitrogen) stimulates luxuriant growth, but has to be balanced by K (Potash), otherwise the plant tissues will become soft (thin cell walls) and will have less resistance to disease and drought. Assisted by calcium, potassium plays an important part in the growth zone at the bases of the leaves and peduncles. A deficiency of potassium will result in flowers blooming between leaves. It also affects the size, intensity of colours, quality and life span of flowers. P (phosphorous) plays an important role in the development of a good root system AND will determine the number of flowers in the umbel and the number of ovules in the locules.
Nutrition and the quality of your seeds (see accompanying figure) 
The food supply of your seeds is exendospermous which means that it is a separate food supply for the embryo plant and is stored outside the cotyledon, (seed leaf of the embryo) but the embryo plant is attached to the food supply by the epicotyl and serves as a channel through which the food – after it has been made soluble by enzymes – can reach the developing embryo plant. Just below the longitudinal slit through which the first seed leaf appears, we find the hypocotyl from which the radicle develops. On the radicle you will see a dense growth of adhesive root hairs. In nature this serves to adhere to anything with which it comes into contact (even a radicle from another seed). The radicle tends to grow straight down to anchor the developing embryo plant firmly. For all this growth, a lot of energy (food) is needed.
The chlorophyll in the leaves of the plant form simple sugars from CO2 and H2O during photosynthesis. Potassium is needed to convert the simple sugars into starch, which is stored in the food supply of the seed. Plant protein is also synthesized from sugars and mineral salts (especially nitrogenous salts) and is likewise stored in the seeds as a good supply for the developing embryo after germination.
It is therefore important to feed your plants well with at least a basic 3.1.5. fertilizer and, if possible, with the necessary trace elements. The Scotts Peters Professional fertilizers (15 .11.29 = N3 : P2 : K6) has the important additional phosphorous and potassium for reasons already explained. I feed my plants at least once a month with a hydroponic mixture just to make sure that the plant medium does not become deficient in trace elements which are equally important (for example: Fe and Mg are both necessary to form chlorophyll).
So, if you feed your plants well during the development of the seeds, they will be larger and germinate and develop faster with an adequate food supply available for development until the first true leaf has developed to a stage where the seedling can manufacture its own food. If the seeds do not have ample food supply, the developing seedlings become runts and the subsequent development will be slow.
Nutrition of seedlings
I recommend spraying seedlings with a plant stimulant like concentrated liquid seaweed extract (Kelpak) which contains auxins such as Gibberellins and Cytokinins or Supranure, which contains indoleacetic acid. (Commence this programme only after all the stored food in the seed has been used up.) Use a hydroponic mixture – mainly for the trace elements – about once a month.
© Copyright by Christo Lötter. Used with permission.