Nitrate Uptake and Partitioning by Corn {Zea mays L.) Root Systems and Associated Morphological Differences among Genotypes and Stages of Root Development

Pan, W. L., Jackson, W. A. and Moll, R. H. 1985. Nitrate uptakeand partitioning by corn (Zea mays L.) root systems and associatedmorphological differences among genotypes and stages of rootdevelopment.—J. exp. Bot, 36: 1341–1351 Nitrate uptake and partitioning by root systems of corn inbredlines were examined. Six-day-old root systems of decapitatedseedlings of seven corn inbred lines were shown to differ markedlyin their capacity for nitrate uptake and partitioning. The magnitudeof nitrate uptake ranged from 44–86 µmol NO^–₃g ^–1 fr. wt. during an 8 h period. Relative nitrate translocation(% of total uptake) also varied among the seven genotypes from4–25%, and differences in the proportions accumulated(28–73%) and reduced (22–58%) were observed. Threeof these genotypes were then examined at 5,6, and 8 d aftergermination to determine the effect of lateral root proliferationon the previously observed differences in nitrate uptake andpartitioning. Nitrate translocation per unit mass increasedwith root elongation and lateral root proliferation, and genotypicdifferences in this partitioning process were associated withdifferences in these morphological parameters. In contrast,differences among genotypes in their capability to accumulatenitrate were not correlated with these differences in morphology.Evaluations of genotypic differences in nitrate uptake and partitioningat the seedling stage should include the rate and characteristicsof morphological development Key words: Lateral root, root morphology, nitrate translocation     

New microsatellite loci confirm hybrid origin,parthenogenetic inheritance,and mitotic gene conversion in the gynogenetic Amazon molly (Poecilia formosa)

We describe the first microsatellite loci for the gynogenetic Amazon molly, Poecilia formosa, an all‐female species arisen through hybridization of the bisexual species Poecilia mexicana and Poecilia latipinna. The loci showed one to six alleles and an expected heterozygosity between zero and 0.75. As expected with parthenogenetic inheritance, most loci were either constantly homozygous (five loci) or constantly heterozygous (eight loci). For six loci, both heterozygotes and homozygotes occurred. This and the fact that some loci only showed alleles of one of the ancestral species could indicate genome homogenization through mitotic gene conversion. Our new loci conformed to the hybrid origin of Amazon molly and are also applicable to both ancestral bisexual species.     

Physiological Stress Response of Captive White-Tailed Deer to Video Collars

ABSTRACT Animal-borne video and environmental data collection systems (AVEDs) are an advanced form of biotelemetry that combines video with other sensors. As a proxy for physiological stress, we assessed fecal glucocorticoid metabolite (FGM) excretion in 7 white-tailed deer (Odocoileus virginianus) fitted with AVED dummy collars; 9 additional deer served as controls. We collected fecal samples over 3 2-week periods: pretreatment, treatment, and posttreatment periods. There were no differences in FGMs across time periods (F_2,218 = 1.94, P = 0.147) and no difference between FGMs of control and treatment individuals (F_1,14 = 0.72, P = 0.411). Fecal glucocorticoid metabolite excretion in AVED-collared deer was indistinguishable from uncollared animals and within the normal, baseline range for this species. Absence of an adrenal response to collaring suggested that AVED collaring does not induce physiological stress in deer.