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Cacodylic acid (hydroxydimethylarsine oxide) was more phytotoxic than monsodium methanearsonate (MSMA), sodium arsenate, or sodium arsenite when foliarly-applied. MSMA was much more effective on dicotyledonous than on monocotyledonous species. Sodium arsenite and arsenate had little effect on grasses. A comparative study of absorption, transport, and metabolism in beans (Phaseolus vulgarisL. ‘Black Valentine’) revealed that cacodylic acid and MSMA were transported about equally from the leaves to the terminal bud and expanding leaves whereas negligible amounts of sodium arsenite and arsenate were translocated. The latter two compounds caused more rapid contact injury to the treated leaves than either organic arsenical. There was no indication that cacodylic acid or MSMA was demethylated to form inorganic arsenicals or reduced to trivalent arsenic compounds. Studies with14C-MSMA indicated that about 40% of the14C and arsenic recovered was bound rapidly to another molecule to form a ninhydrin-positive complex. In small amounts, arsenate combined with some component of plant tissues. Also, arsenite probably was oxidized to arsenate. In beans, root-applied sodium arsenite was more phytotoxic than sodium arsenate and both were much more phytotoxic than cacodylic acid and MSMA. Most differences in phytotoxicity could not be explained by differences in rates of absorption by bean roots. Arsenite caused considerable contact injury to the root system, probably accounting for its relatively great phytotoxicity. Both cacodylic acid and MSMA were more phytotoxic per mole of tissue arsenic when foliarly-applied than when root-applied.

Sachs, R. M., A. Lang, C. F. Bretz and Joan Roach. (U. California, Los Angeles.) Shoot histogenesis: subapical meristematic activity in a caulescent plant and the action of gibberellic acid and Amo—1618. Amer. Jour. Bot. 47(4): 260—266. Illus. 1960.–Studies on gibbereilininduced stem formation in rosette plants (Sachs et al., 1959) have shown that a zone of intensive meristematic activity, arising below the existing apical meristem, is almost solely responsible for stem histogenesis, i.e., the formation of the cells constituting the elongate stem. An extensive subapical zone of meristematic activity is also present in caulescent plants, such as Chrysanthemum morifolium, Amo‐1618 ([4‐hydroxy‐5 isopropyl‐2 methylphenyl] trimethylammonium chloride, 1‐piperidine carboxylate) completely inhibits subapical meristematic activity in chrysanthemum, causing the plants to assume a dwarfed, rosette‐like habit of growth. Gibberellic acid, applied either simultaneously, or following the Amo—1618 treatment, completely prevents or reverses the effect of Amo—1618, making the plants retain or resume their normal growth habit. Amo—1618 and gibberellic acid have relatively little effect upon the activity of the apical meristem of Chrysanthemum. Thus, while the apical meristem proper (eu‐ or promeristem) is the site of shoot organization and the ultimate source of the cells of the entire shoot, the subapical zone of division, termed the subapical meristem, is largely responsible for stem histogenesis in caulescent as well as in rosette plants. Gibberellins, or native, gibberellin‐like substances appear to regulate the activity of the subapical meristem and thus to play an important role in shoot development. Amo—1618 and related compounds seem to exert their dwarfing effect in plants by acting as antagonists of gibberellins, at least with respect to the latters' function in regulating the subapical meristematic activity in the shoot.

Flowering of brodiaea (Triteleia laxa syn. Brodiaea laxa `Queen Fabiola') did not have an obligate requirement for manipulation of temperature or photoperiod. Vernalization of corms reduced the greenhouse forcing phase but did not alter the number of flowers per inflorescence or scape length. Long photoperiods hastened flowering but decreased flower quality and flowering percentage. Scape length, which was not affected by photoperiod or mother corm size, was increased when plants were grown at night temperatures < 10C. Diameter of the apical meristem in the dormant corm, flowering percentage, and flower quality were not affected by a 10-fold increase in corm size above a critical weight (0.6 g). In contrast, the weight and number of daughter corms were closely correlated with mother corm size. The optimum planting depth for brodiaea corms was 10 cm below the soil surface.