Effects of temperature on the cytokinin requirement of tobacco calluses

A cytokinin-nonrequiring strain (T22) was isolated from a cytokinin-requiringcallus strain T2 of tobacco (Nicotiana tabacum var. Bright Yellow). Strain T22 grew rapidly on the medium without added kinetinat 26?C. But its growth was completely suppressed at 16?C. Thisgrowth suppression at 16?C was partially recoverable by supplyingkinetin. Benzyladenine, geranylaminopurine and 2-methyl-8-benzylamino-s-triazolo[l,5-a]pyrazinewere also effective in removing growth suppression at 16?C.Adenine, which was unable to remove growth suppression of T22at 16?C, promoted the growth of T2 at 26?C, but not at 16?C.Physiological differences between cytokinin-requiring and -nonrequiringcalluses are discussed. ¹Part II in the series "Studies, on Plant Tissue Cultures";for Part I, See Plant & Cell Physiol. 9: 103–114 (1968). (Received May 29, 1970; )