The effect of a number of auxins and auxin analogues on the basipetal transport of illdole-3-aeotie acid (IAA) in 5-mm segments of hypocotyls of i)-day-old etiolated Phaseolus vulgari8 L. seedlings has been investigated.
Previous studies have shown an increase in RNA at the shoot apex of L. temulentum following floral induction, detectable chemically 2 days after induction, and by histochemical means after 1 day. Here, a transient increase in the incorporation of 32P, applied to leaves, into nucleic acids at the apex is shown to occur at about the time when the long-day stimulus is estimated to reach the shoot apex. The increased 32p incorporation due to the long-day exposure occurs throughout the apex, and is not confined to the summit region. Most of the 32p was incorporated into RNA.
Subsequent to oarlier work 011 Oal)seUa. bWI'8a..pl1slol'is (L.) ]\;Joeneh. embryos of' nino plallt fmnilies, monocotyledons 11m] dicot,ylodolls, oxcisod from young developing ovuLes were growll ill a "sittiug drop" culture.
Young excised embryos of Anagallis arvensis L. (Primulaceae) and of the cruciferous species Arabidopsis thaliana (L.) Heynh., Oapsella bursa.pastoris (L.) Moench., and Sisymbrium orientale L. were fed with inorganic and organic nitrogenous compounds whilst they were kept in "sitting drop" cultures for periods of 48 and 96 hr.
SummaryFeeding experiments and enzyme tests were carried out to investigate the utilization of y-aminobutyric acid (ABA) by wheat seedlings.In the feeding experiments embryos were excised from the grain 20-24 hr after soaking, explanted on a basal medium to which different nitrogen sources were added, and incubated at 25°C.ABA nitrogen was utilized for protein synthesis. The optimal concentration was 6·0 mM. Different amino acids· tested at equivalent nitrogen concentration produced the following sequence in insoluble nitrogen content per seedling:Growth in length of the first leaf was on all occasions stimulated by ABA, but root growth was not.Extracts of roots of 2-and 3-day-old intact seedlings had about 2· 5 times the glutamic acid decarboxylase activity (per seedling) as that of shoot extracts; on a protein basis the ratio became more than 6.No ABA-glutamic acid transaminase could be shown in root and shoot extracts, even after attempts to induce the enzyme, but alanine-glutamic acid transaminase activity was high in similar extracts. Neither was any evidence found for the presence of ABA oxidase in the seedlings.
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