ABSTRACT
The effect of different concentrations of nickel nitrate (0.25, 0.50, 1.00 and 2.00 mM) uptake by the roots, on root growth of onion (Allium cepa) and the transport of Ni2+, Fe2+, Mn2+, Zn2+, K+, Na+ and H+ ions were investigated spectrophotometrically. The uptake of Ni2+, Fe2+, Mn2+ and Zn2+ was monitored by flame atomic absorption spectrometry with a 24-h period for 7 days and the amounts of K+ and Na+ were determined in solutions by flame photometer. The mineral content of the solution, instead of the root material was measured. Ni2+ ions showed inhibitory effect on the root growth at all concentrations during the entire treatment. The EC50 (effective concentration that reduced root growth by 50%) was found at 0.25 mM Ni2+. No significant change in inhibitory effect was observed after at 0.50 mM Ni2+ concentrations. A large amount of Ni2+ was translocated into the roots. The kinetics of metal ion transport followed a pseudo-first order reaction in all metal ion concentrations. Ni2+, Zn2+ Fe2+ Mn2+ and H+ ions transferred together into plant, but Na+ and K+ ions transferred to the solution from the plant. The amount of H+ in the solution decreased at all Ni2+ concentrations.
ABSTRACT
The aim of this study is to give information on ultrastructure of in vivo pollen tubes of Mimulus aurantiacus which were collected from the Botanical Garden of the University of California at Berkeley. Materials were prepared according to electron microscopy methods and examined under Zeiss electron microscope. Four zones were examined in the pollen tubes of Mimulus aurantiacus. APICAL ZONE: Mitochondria, smooth endoplasmic reticulum, rough endoplasmic reticulum, dictyosomes and secretory vesicles were observed. SUBAPICAL ZONE: This area contained abundant rough endoplasmic reticulum and occasionally some smooth endoplasmic reticulum. The polysomes, mitochondria, proplastids that contain starch, small vacuoles and a few lipid bodies were detected. NUCLEAR ZONE: Both generative and vegetative cell nuclei lie in this zone. The vegetative cell nucleus was large and long. Rough endoplasmic reticulum, mitochondria, ribosomes, dictyosomes, and amyloplasts that are rich of starch were observed. VACUOLATION AND PLUG FORMATION ZONE: Cytoplasm of the tubes was full of large vacuoles. Few organelles such as mitochondria, dictyosome and rough endoplasmic reticulum were detected along their periphery.
O objetivo deste estudo é informar sobre a ultraestrutura de tubos de pólen de Mimulus aurantiacus in vivo coletados no "Botanical Garden" da Universidade da Califórnia em Berkeley. O material foi preparado de acordo com os métodos de microscopia eletrônica e examinado em microscópio eletrônico Zeiss. Quatro zonas dos tubos de pólen de Mimulus aurantiacus foram examinadas. ZONA APICAL: foram observados mitocôndrias, retículo endoplasmático liso; retículo endoplasmático rugoso, dictiossomos e vesículas secretoras. ZONA SUBAPICAL: esta área continha retículo endoplasmático rugoso em abundância e, ocasionalmente, algum retículo endoplasmático liso. Foram detectados polissomos, mitocôndrias, proplastídeos que contêm amido, pequenos vacúolos e alguns corpos lipídicos. ZONA NUCLEAR: nesta área, existem tanto núcleos de células geradoras como vegetativas. O núcleo de célula vegetativa é grande e longo. Foram observados retículo endoplasmático rugoso, mitocôndria, ribossomos, dictiossomos e amiloplastos ricos em amido. ZONA DE VACUOLIZAÇÃO E DE FORMAÇÃO DE "PLUG": o citoplasma dos tubos estava cheio de grandes vacúolos. Algumas organelas como mitocôndria, dictiossomo e retículo endoplasmático rugoso foram detectadas em toda a periferia desta área.