Effects of over-winter fumigation with sulphur and nitrogen dioxides on biochemical parameters and spring growth in red spruce (Picea rubens Sarg.)

Abstract. Red spruce ( Picea rubens Sarg.) seedlings were overwintered in two controlled environment chambers designed to simulate sub-zero winter conditions. One of the chambers was fumigated throughout the 5-month period with low concentrations of SO₂+ NO₂. Extracts of extracellular fluid from trees in this treatment revealed accumulations of sulphite and nitrite, but not of sulphate or nitrate. Analysis of the chloroplast membrane lipid monogalactosyl diglyceride (MGDG) indicated a large increase in fatty acid saturation in both treatments during mid-winter, with a subsequent recovery to earlier levels. Although at the end of the experiment the MGDG of polluted trees contained significantly less linolenic acid, there was no overall treatment effect on fatty, acid content. In the following spring, there was some indication that flushing of leader buds began earlier and proceeded at a slower rate in polluted trees compared to controls, but no other growth parameters were affected by the winter treatment. The absorption of SO₂ and NO₂ and the accumulation of their products during dormancy is discussed as a potential mechanism for metabolic disruption, resulting in changes to seasonal responses which could be critical to the survival of the plant.     

History of a Late Carboniferous phylloid algal bank complex in northeastern New Mexico

The growth history of a phylloid algal biohermal complex of Late Carboniferous (Westphalian) age, outcropping within the La Pasada Formation in northeastern New Mexico, U.S.A., is described in relationship to paleogeography, biostratigraphy, and microfacies associations. This phylloid algal biohermal complex occurs within typical Late Paleozoic cyclical sediments, in a paleogeographic setting along a narrow shelf margin bordering a deep geosynclinal trough to the northwest. Fusulinid foraminifers suggest that the bioherm is of Middle Pennsylvanian (lower Des Moines) age, whereas the overlying sediments are of middle Des Moines age. Both field and petrographic evidence suggest that the bioherm grew upward from relatively shallow water depths, into extremely shallow water where it probably was subaerially exposed. Biohermal growth appears to have been initiated on a 'hard-ground' surface on which lithified clasts and abundant clusters of robust linoproductid brachiopods served as a foundation. Four major microfacies have been identified from the biohermal complex. These are: (I) phylloid algal wackestones-packstones (mound proper), (2) marly limestones (sediments laterally adjacent to and overlying mound), (3) pelletal-foraminiferal wackestone (partially capping the mound), and (4) crinoidal packstones-grainstones (post-mound). Comparison is made with other surface and subsurface occurrences of phylloid algal complexes of similar age in the southwestern United States.     

Zinc-induced Vacuolation in Root Meristematic Cells of Cereals

In the absence of Zn, vacuolar volume fractions of root meristematiccells of Secale cereale L. cv. K2, Triticum aestivum L. cv.Chinese Spring and Oryza sativa L. cv. IR34 were 5.64 x 10^–2,2.17 x 10^–2 and 1.63 x 10^–2 µm³ vacuole µm^–3tissue, respectively. A 4-d exposure to a subtoxic concentrationof zine (0.2 µg Zn cm^–3) induced a 2.93-fold anda 6.78-fold increase in the total vacuolar volume fraction inOryza and Triticum, respectively, whereas no significant increasewas observed for Secale. It is proposed that this Zn-inducedvacuolation represents a compartmentalization mechanism. Theinitial total vacuolar volume fraction in Secale was greaterthan that for Oryza and Triticum and this may enable compartmentalizationof the metal soon after the onset of treatment so reducing itscytotoxic effects. These findings are similar to those observedin contrasting cultivars of Festuca rubra L. Triticum aestivum L, Secale cereale L, Oryza sativa L, zinc, root meristem, vacuolation     

Changes in Cell Number and Cell Division Activity during Endosperm Development in Allohexaploid Wheat, Triticum aestivum L.

Nuclear or cell number, and the mitotic index, were recordedin endosperms of Triticum aestivum cv. Mardler to test if aparticular stage of endosperm development was critical in determiningthe final grain weight. The basal four florets of emasculatedspikelets (controls), and the third and fourth florets of spikeletswhere the two basal ovaries were removed (ovary-removed), weresampled at various times up to 360 h after hand-pollination.The coenocytic phase in endosperms ended about 84 h after pollinationregardless of both grain position and the treatment. The onsetof the cellular stage was characterized by the final large fluctuationsin the mitotic index reflecting the culmination of the synchronousnuclear division of the coenocytic stage. Thereafter, the mitoticindex fluctuated with smaller amplitudes and, by 216 h afterpollination, was < 1%. Neither floret position in the spikeletnor the treatment affected the pattern of alteration to themitotic index. However, ovary removal from first and secondflorets resulted in significantly heavier grains and higherendosperm cell number in the 3rd and 4th florets compared withthe controls. In all florets, mean endosperm cell number peakedat 280 h but decreased by 360 h after pollination. At this time,the mean cell numbers in endosperms of the 3rd and 4th floretsof ovary-removed spikelets were significantly higher than inthe corresponding endosperms in the controls. Thus, a key contributoryfactor in determining the final endosperm cell number may bethe number of cells which are lost during the late period ofthe cellular stage of endosperm development. Key words: Endosperm cell number, florets, grain weight, mitotic index, Triticum aestivum     

Some Cytological Changes accompanying the Regeneration of Meristematic Activity at the Apex of Decapitated Roots of Vicia faba L.

The changes that took place in mitotic index (MI), labellingindex (LI) and the relative proportions of interphase nucleiwith different amounts of DNA have been investigated duringthe regeneration of meristematic activity at the apex of rootsof Vicia faba over the 144 h period following removal of thecap and apical mm of the meristem. Measurements were also madeof the corresponding changes that took place as cells were displacedbasally along the root from the apex over the experimental period.In both parts of the root, MI and the relative proportions ofnuclei with different DNA contents changed from levels similarto those at the apex of the controls at the start and end ofthe experiment to levels resembling those found in more matureparts of the root at 24 and 48 h. In contrast to these results,LI declined over the experimental period. These cytologicalchanges were aresult of the development of lateral root primordiain both the apical 2 mm of the decapitated roots and as cellswere displaced out of the meristem into more basal parts ofthe root. It was concluded that the events leading to the regenerationof meristematic activity at the apex of roots from which thecap and apical mm of the meristem were removed, are no differentfrom those which result in lateral formation as cells are displacedbasally along the primary root from the apex, and they takeplace over the same time interval in both systems.     

Dorisiella arizonensis n.sp., a Coccidium from the Desert Woodrat, Neotoma lepida

SUMMARY. Dorisiella arizonensis n. sp. (Sporozoa: Eimeriidae) is described from oocysts in the feces of a desert woodrat, Neotoma lepida , from Grand Canyon National Park, Arizona. The oocysts are spherical to subspherical, measure 20.8–21.8 × 20.8–22.9 μ, with a mean of 21.0 × 21.8 μ, and have a two-layered wall. They contain 1 to 3 refractile granules but no residual body. The two lemon-shaped sporocysts have a Stieda body, 8 sporozoites, and a few to many scattered, round, clear residual granules or bodies.     

Temporal and spatial fluctuations of heavy metals in Opa Reservoir,Ile-Ife,Nigeria

The Opa Reservoir, established for water supply to the Obafemi Awolowo University community, over the years has received direct linkage to township drains as a result of the widening and dredging of its river channels. The current study aimed at documenting monthly heavy metal loads at its riverine, transition and lacustrine zones in 2012–2013. Most of the heavy metals, analysed using an atomic absorption spectrophotometer, occurred within wide ranges, with coefficients of variation ranging from 60% to 300%, although the differences in heavy metal loads between the different zones were statistically insignificant at both the surface and bottom levels. The overall order of dominance of the metals was Ni > Cu > Fe > Zn > Cd = Cr > Pb, with nickel concentration being very high throughout. Heavy metal total mean concentration was higher during the rainy season (1.889 mg l?1) than the dry season (1.503 mg l?1) irrespective of sampling sites, having highly significant seasonal differences (p < 0.001) in Ni, Cd, Fe and Cu concentrations. The mean concentrations of Zn (0.074 mg l?1), Fe (0.176 mg l?1), Cu (0.507 mg l?1) and Pb (0.004 mg l?1) were within the WHO acceptable limit. However, the recorded levels of toxic elements Cd (0.031 mg l?1) and Ni (0.905 mg l?1) pose potential health risk to water consumers.     

Changes in the Pattern of Cell Division in the Shoot and Root Meristems of Lolium perenne during the Transition from Vegetative to Floral Growth

For Lolium perenne cv. Cropper, a system which resulted in 100%flowering comprised 90 short days (SD) at 4 ?C (vernalization)and 30 SD at 18 ?C followed by 8 long days (LD). The mitoticindex and G1 and G2 percentages were measured in the shoot androot apices of plants following 2, 5 or 8 LD and in SD controlssampled at the beginning and end of induction. Identical measurementswere made in plants given 48 SD at 18 ?C followed by 2, 5 or8 LD; plants remained vegetative in response to this treatmentlacking vernalization. Significant increases in both mitoticindex and meristem size occurred in the shoot apex in LD followingthe vernalizing, but not the non-vernalizing, treatment. A clusterof mitoses in the apical dome of the shoot apex was unique tothe vernalized plants given 5 or 8 LD. However, an increasein root meristem size occurred regardless of vernalization,but a significant increase in the mitotic index was limitedto vernalized plants given 5 or 8 LD. Whilst the vernalization-LDtreatment resulted in an increase in the G2 percentage in theshoot apex following 2, 5 or 8 LD, no such alteration was observedin the root meristem. Thus, the changes to the cell cycle whichcorrelated with flowering were increased mitotic indices andG2 percentages in the shoot apex at each sampling time and increasedmitotic indices in the root apex following 5 and 8 LD. Key words: Cell division, flowering, Lolium perenne L.