INVESTIGATIONS ON AUXIN-GIBBERELLIN INTERACTION ON THE PHOTOTROPISM OF HELIANTHUS ANNUUS HYPOCOTYL

On applying IAA-GB and IAA-NAA mixtures to the hypocotyls ofHelianthus annuus, the plants showed an increase and a decrease,respectively, in their phototropic response compared with thecontrol treated with IAA-H₂O only. In the in vitro experimentsit was observed that the illumination (with 1,500 lux light,lasting for 24 hr) caused photoinactivation of IAA in the mixturesof IAA-H₂O, IAA-GB and IAA-NAA by 50%, 24% and 0%, respectively.In the presence of 0.01% riboflavin as a photosensitizer inthe same mixtures, the degree of photodestruction of IAA causedby the same illumination was 92%, 97% and 86%, respectively. The stronger positive phototropism in the IAA-GB treated hypocotylwas accounted for by the situation that on the illuminated sidethe photo-inactivation of IAA was accelerated by GB, while onthe shaded side IAA and GB acted synergistically. On the otherhand, the weaker phototropism in the IAA-NAA treated hypocotylwas explained as due to a partial inhibition of photoinactivationof IAA by NAA. (Received October 6, 1962; )     

The Effect of Gravity Compensation on Growth and Cell Wall-loosening Enzymes in Helianthus annuus Hypocotyls

The effect of gravity compensation by the clinostat on the elongation, weight, and activity of two cell wall-loosening enzymes (cellulase and β-1,3-glucanase) in Helianthus annuus hypocotyls was examined. Gravity compensation increases elongation (28.1 %) and weight (18.3 %). The activity of cellulase extracted from the apical sections is raised, but there is no significant effect on β-1,3-glucanase. The relationship between gravity compensation, changes in auxin level, and function of these two enzymes in respect to elongation is discussed.     

Ctenophthalmus harputus, a new Spalax flea from Turkey

ABSTRACT. Ctenophthalmus harputus sp.n. is described from the mole rat Spalax ehrenbergi Nehring collected near Elaziǧ city in eastern Turkey. This new flea species is classified in the Ctenophthalmus (Palaeo-ctenophthalmus) fissurus Wagner group. A key is given to the six species of Spalax fleas (Siphonaptera: Hystrichopsyllidae, Ctenophthalmus spp.) recorded from Turkey.