Text 8. Keeping the seeds

To keep seeds is to prevent germination and at the same time to preserve the life of the seeds. Seeds should be thoroughly ripe and dry before they are stored. Those of pulpy fruits are removed and cleaned. If the seed-vessels are dry and hard, seeds may be left in them till sowing time, but usually they are removed.

Hard seeds, as of trees and nuts, may be buried, that is, mixed with earth exposed to frost or to moisture for a considerable time. Most seeds, however, are stored dry in paper bags or boxes in a cool dry room. The receptacles should be tight to keep out weevils; if there are any signs of bug work, a little bisulfide of carbon may be poured in the receptacle, and the vapor of it will destroy animal life. This material is inflammable, and it should be kept away from flames. If seeds at storing time are moist and the weather is damp, they may be lightly kiln-dried before put away for winter.

The influence that light exerts on germination is not definitely understood for all horticultural seeds. It is known, however, that seeds will often germinate in full sunlight, if the proper conditions of moisture and temperature can be maintained. Seeds sown on a moist surface and covered with a grass present an interesting study. They may have difficulty in getting a foodhold, and they present peculiar reactions to light.

It is well known, on the other hand, that some seeds will not germinate, or will at least appear unevenly, if subjected to sunlight. At least some of the delphiniums and Adonises germinate very imperfectly, if at all, in direct light. It is always advisable to keep germinating seeds in shade or partial darkness. Of course, the soil itself is sufficient protection if the seeds are covered.

Text 9. Nematodes

Nematodes are small parasitic roundworms about one – sixty-fourth to one-eighth inch long. They live in the soil and usually move into the plant through the roots. Underground parts are more apt to be infected, but the infection of stems, leaves, and flower parts is fairly common. The nematodes that attack alfalfa live mainly in the plant tissue and suck juices from the cells. Alfalfa may be attacked by the root- knot nematode, the dagger nematode, or the stem nematode. Nematode damage in alfalfa has been a serious problem in Nevada, Utah and California.

Plants infected with the root – knot nematode develop galls or knot like growths on the roots. Severe infections cause the roots to become thickened, rough, and club like. Considerable rotting may occur, especially late in the season. The formation of nodules by nitrogen-fixing bacteria on alfalfa and other legume roots should not be confused with the galls and knot like growths caused by nematodes. Plants infected with stem nematodes may have swollen stem and buds, shortened internodes, and deformed leaves or other plant parts.

Text 10. Verticillium wilt

Verticillium wilt is a relatively new disease of alfalfa in the United States. It is considered to be a serious disease in Europe where it has been known since 1918. It was first discovered in the United States in the Pacific Northwest in1976 and was positively identified in Wisconsin in 1980. The disease is caused by a fungus that invades the vascular system of the plants and reduces the flow of water and mineral nutrients to the leaves. Early symptoms are temporary wilting of upper leaves on warm days and a yellow or pinkish- orange discoloration on some leaflets. Chlorotic, V-shaped lesions extend from the leaflet tip down the midrib. The leaflets soon become yellow, bleached, desiccated, and twisted. They are early detached from the stem, which often remains erect and green long after all the leaves have died. A key characteristic of verticillium wilt is that not all plants in a stand are affected, and within an infected plant only one to a few of the shoots shows the symptoms during the early stages. Later, as diseased plants and shoots become more prevalent, the more seriously affected plants also are stunted.