EFFECT OF INITIAL SIZE ON GROWTH OF PLANT TISSUE CULTURES

Caplin , Samuel M. (LOS Angeles State Coll., Los Angeles, Calif.) Effect of initial size on growth of plant tissue cultures . Amer. Jour. Bot. 50(1): 91–94. Illus. 1963.—Using different slice thicknesses and cannula diameters, cylindrical expiants of different size were obtained from tubers of Jerusalem artichoke. Slice thickness ranged from 0.5 to 2.5 mm and expiant diameter from 1.30 to 3.22 mm. Initial fresh weights ranged from 2.3 to 29.8 mg, a 13-fold range. After 17 days growth at 26 C in 10 ml basal medium containing 15% coconut milk, relative increase was inversely related to initial weight and ranged from 36-fold for 2.3-mg expiants to 8-fold for 29.8-mg expiants, a range of 4.5 × in relative increase between the largest and smallest cultures. Secondary phloem expiants of the same diameter from carrot root slices of different thickness, all removed at 1 mm from the cambium, also showed decreased relative growth with increasing size of explant; this was true for each of the different diameters used. Further investigation showed clearly that the growth of the large inocula was not limited by the amount of culture medium used during the period of culture. Initial weight has, therefore, a decided effect on the rate of relative growth.