EFFECT OF X-IRRADIATION UPON GROWTH AND REPRODUCTION OF TOMATO

Abstract

Irradiation of young tomato seedlings causes marked leaf anomalies in the young growth which develops after irradiation. Leaflets are often absent, badly twisted, or joined together in unusual fashion. Soon after irradiation, the leaves present a peculiar warty or pebbly appearance. As they grow older, there are areas of green of varying intensities so that they appear spotted or variegated. Plants receiving x-ray dosage develop many lateral branches which cause them to assume a bushy appearance. The number of branches developed may be 65% greater in the irradiated plants than in the controls. Many abnormalities of floral parts, including production of double blossoms, occur when plants are thrice irradiated previous to blossoming. If, however, radiation occurs at time of budding when there has been no previous dose, the buds become yellow and drop off without blossoming. Later growth may produce blossoms, some of which are normal while others are double or triple. Fruit development is somewhat delayed in plants which are irradiated during their early seedling stages. However, in plants which were irradiated just before blossoming with one medium dose, complete sterility was present for some time. Later the new growth produced small abnormal fruits on 25% of the plants as compared with 100% fruit production of the controls. Radiophylaxis. a lessening of the effect of a harmful dose by giving a preceding lighter one, was demonstrated by tomato flowers in one scries. A dose which would ordinarily cause a yellowing and dropping of buds if given as the buds were forming, did not have such a markedly fatal effect when 2 earlier doses were given before the reproductive stage. Fruits which do develop on irradiated plants show a lack of definite internal pattern; the placenta and core show abnormal development and there is an almost total absence of seed. Pockets formed in the pericarp of fruits from irradiated plants are not found in the controls.