16 



MISCELLANEOUS PUBLICATIONS 1251, U.S. DEPT. OF AGRICULTURE 



should be watered sparingly to prevent root 

 rot. Seed viability is much reduced after 1 year. 



Plantain and Sunflower. — These species have 

 very low nutritional requirements and are sus- 

 ceptible to mildew when grown under high 

 humidity. 



Potato. — When greenhouse-grown tubers are 

 replanted in the greenhouse, the resulting vines 

 may be spindly and tuber production poor. 



Soybean. — When illumination is insufficient, 

 internodes become greatly elongated, leaves be- 

 come enlarged, and the plants will fall over. At a 

 high nutrient concentration the young leaves 

 become cupped. 



Sugarcane. — Solution culture of seedlings in 

 ti'oughs for more than 30 days is difficult because 

 trough covers (fig. 2) will interfere with stem 

 thickening. If seedlings are grown in fertile soil, 

 little nutrient addition may be required in the 

 first 4 weeks. Then, one-half strength solution can 

 be supplied three times per week for the next 4 

 weeks followed by a full-strength solution on 

 the same schedule for the remainder of the growth 

 period. In vermiculite use one-half strength 

 solution three times per week. For further propa- 

 gation, 10-cm. stem sections of mature plants, 

 each bearing a node, may be layered in moist 

 vermiculite, covered, and incubated for 5 to 7 



days at 32° C. The sprouted sections will grow 

 rapidly when transplanted to vermiculite and 

 supplied with one-half strength solution. Sugar- 

 cane forms more tillers in vermiculite than in 

 solution culture. 



Sweet potato. — This species is easily propagated 

 by layering a vine and transplanting the vine 

 sections that sprout at each internode. New 

 sprouts 15 to 20 cm. long also may be removed 

 from the root and planted. When sweetpotato is 

 grown in liquid culture, the fleshy roots do not 

 develop well. 



Tobacco. — Reduce moisture stress for 48 hours 

 after transplanting by lowering the temperature 

 to about 18° C. and increasing the humidity. 



Tomato. — Uneven watering of plants in ver- 

 miculite will result in ovary rot of developing 

 fruit. Pollination can be promoted by tapping 

 the plants or by using a fan. A determinate 

 variety such as 'Sheyenne' is especially suitable 

 where compact plants are desired. 



Turnip. — This species has low nutritional re- 

 quirements. Roots enlarge rapidly in solution 

 culture. 



Wild Buckwheat. — Newly harvested seed may 

 remain dormant. Vines should be staked up 

 adequately and spaced to prevent tangling. 



LITERATURE CITED 



(1) Andersen, R. N. 



1968. GERMINATION AND ESTABLISHMENT OF WEEDS 

 FOR EXPERIMENTAL PURPOSES. 236 pp. 



W. F. Humphrey Press, Inc., Geneva, N.Y. 



(2) Baker, K. F. 



1957. THE U.C. SYSTEM FOR PRODUCING HEALTHY 

 CONTAINER-GROWN PLANTS. 332 pp. Calif. 



Agr. Expt. Sta. Ext. Serv., Berkeley, Calif. 



(3) Barton, L. V. 



1967. bibliography of seeds. 858 pp. Colum- 

 bia Univ. Press, New York. 



(4) Downs, R. J., Borthwick, H. A., and Piringer, A. A. 



1961. light and plants. U.S. Dept. Agr. Misc. 

 Pub. 879, 26 pp. 



(5) Evans, L. T., ed. 



1963. environmental control of plant growth. 

 449 pp. Academic Press, New York. 



(6) Hartman, H. T. 



1968. plant propagation: principles and prac- 

 tices. Ed. 2, 702 pp. Prentice Hall, 

 Englewood Cliffs, N.J. 



(7) Hewitt, E. J. 



1966. SAND AND WATER CULTURE METHODS. Ed. 2 



(rev.), 547 pp. Commonwealth Agr. Bur., 

 Farnham Royal (Bucks), England. 



(8) Hoagland, D. R. 



1948. inorganic nutrition of plants. 226 pp. 

 Chronica Botanica Co., Waltham, Mass. 



(9) and Arnon, D. I. 



1938. the water-culture method for growing 

 plants without soil. Calif. Agr. Expt. 

 Sta. Cir. 347, 39 pp. 



(10) Hudson, J. P., ed. 



1957. control of the plant environment. 240 

 pp. Butterworth's Sci. Pub., London, 

 England. 



(11) Sachs, J. von. 



1887. lectures on the physiology of plants. 

 836 pp. Clarendon Press, Oxford, England. 



(12) Schwarz, M. 



1968. guide to commercial hydroponics. 136 

 pp. Israel Univ. Press (Daniel Davey and 

 Co., Inc., Hartford, Conn.). 



