Some Relationships of Sterols to Plant Growth.

In spite of the universal occurrence of steroids in plants, the role of these materials remains quite unknown. That steroids possess physiological activity for the higher plant was in fact demonstrated only after the discovery of estrogenic principles in plants in 1926-1927 by LOEWE and SPOHR (22), DOHRN et al. (12), and LOEWE et al. (20, 21). The status of our knowledge of the influence of the animal steroid hormones on the vegetative growth and reproductive development of plants has been extensively reviewed by LOVE and LOVE (23). There appear to be several well established examples of the influence of estrogenic materials on vegetative growth. Effects of flowering appear to be generally secondary to this effect. HYML6 (17) has, however, demonstrated an influence of estrone and of testosterone on sexual expression in spinach, and LOVE and LOVE (23) have been able to suppress either anther or gynecium growth in Melandrium by application of estrone or testosterone respectively. In addition to the effects which estrone exerts when applied directly to intact plants, there are additional instances of effects of estrone on growth of isolated plant parts or tissues. Such effects have been observed by K6GL and HAAGEN-SMIT (18) and by BONNER and AXTMAN (10) with isolated pea embryos, by FIEDLER (14) with isolated root tips of corn, by WEYLAND (25) with Allium cepa roots, and by GIOELLI (15) with cultures of carrot root. In all of these instances additions of estrone to the culture medium have served to cause a general increase in growth rate. That the synthetic estrogen, diethylstilbesterol, can replace estrone in promotion of plant growth has been established by ZOLLIKOFER (26). The effects of testosterone treatment of higher plants, other than the influence of sex expression noted above, have been quite varied. VON EULER (13), for example, found that inhibition of seedling development resulted when seeds of Lepidium sativum or Hordeum vulgare were treated with testosterone at concentrations of 0.01% as well as with estrone. Similarly, GLASER and RANFTL (16) found testosterone harmful to growth of hyacinth bulbs while DAVID and GouzON (11) found testosterone to be without effect on the species studied by them. Certain microorganisms are influenced by additions of steroids to the nutrient medium. The Rhodotorula sugari and R. glutinis, two of several yeasts investigated by WEBER (24), responded (particularly in the presence of Zn) with increased growth to applications of estrone, estradiol benzoate,