It has been shown recently that treatment with gibberellic acid (GA) results in an increase in diffusible auxin in the pea (7), sunflower (7) and Centaurea (8). Treatment with GA also increases the amount of extractable auxin in peas (14), the potato tuber (18), Rhus typhina (13) and Trifoliuws ochroleucunm (15). Further it has been (lenmonstrated that in the dwarf pea and Cenitauirea the incre...

1. The growth of Avena coleoptile sections in sucrose and auxin solutions is inhibited by various substances which are known to act as dehydrogenase inhibitors. 2. Iodoacetate, which is particularly active in this connection, inhibits all growth at a concentration of 5 x 10(-5) M, but produces only a slight inhibition of oxygen uptake. 3. The growth inhibition by iodoacetate is completely remov...

Summa(iry. Hlydroxy-L-proline-induced inhiibition of elongationi of Aven(a coleoptile segments was measuired in water and in indole-3-acetic aci(l. This inhibition was completely reversed by L-proline. Time-sequence experiments revealed that some time had to elapse, or some eloingationi had to occur, prior to the onset of hydroxyproline inhibition. The presence of sucrose supported the rate of ...

Ethylene and abscisic acid (ABA) have a complicated interplay in many developmental processes. Their interaction in rice is largely unclear. Here, we characterized a rice ethylene-response mutant mhz4, which exhibited reduced ethylene-response in roots but enhanced ethylene-response in coleoptiles of etiolated seedlings. MHZ4 was identified through map-based cloning and encoded a chloroplast-lo...

During anoxia, cytoplasmic pH regulation is crucial. Mechanisms of pH regulation were studied in the coleoptile of rice exposed to anoxia and pH 3.5, resulting in H(+) influx. Germinating rice seedlings survived a combination of anoxia and exposure to pH 3.5 for at least 4 d, although development was retarded and net K(+) efflux was continuous. Further experiments used excised coleoptile tips (...

The biological activity of 20 l-alpha-amino acid conjugates of indole-3-acetic acid (IAA) to stimulate cell elongation of Avena sativa coleoptile sections and to stimulate growth of soybean cotyledon tissue cultures has been examined at concentrations of 10(-4) to 10(-7)m. In the Avena coleoptile test, most of the amino acid conjugates stimulated elongation. Several of the conjugates stimulated...