CONDITION AND WATER DEFICIENCY OF BALSAMIC POPLAR LEAVES IN THE CONDITIONS OF POLYMETALLIC CONTAMINATION OF THE STERLITAMAK INDUSTRIAL CENTER

The paper presents materials on the water deficiency of leaves in the balsamic poplar in the conditions of polymetallic contamination of the Sterlitamak industrial center. The object of the research was poplar plantations located at different distances from the industrial enterprises of Sterlitamak. As a result, it was revealed that in the conditions of polymetallic contamination of the Sterlitamak industrial center at noon, with an increase in temperature and a decrease in relative humidity, the moisture consumption increases in the balsamic poplar. The maximum water deficit in the daytime is from 13 to 15 hours. In trees in conditions of polymetallic contamination of the SPC, the water consumption during the night hours is not covered by its intake, so the next day the morning hours began with some water shortage. As a result of the conducted studies, it was found that in the conditions of polymetallic pollution of the Sterlitamak industrial center, with the deterioration of the living condition and with a decrease in the proportion of absorbing roots of the balsamic poplar, significant changes in water deficit indicators are noted.

CONTENT AND DISTRIBUTION FEATURES OF MANGANESE, NICKEL IN ORGANS IN HEALTHY AND WEAKENED BALSAM POPLAR TREES (POPULUS BALSAMIFERA L.)

The work presents the results of many years of research on the assessment of the vital state, accumulation and distribution of manganese, nickel in absorbing, semiskeletal, skeletal roots and in the aerial, organs in healthy and weakened balsamic poplar trees (Populus balsamifera L.) under the conditions of the Sterlitamak industrial centre. It was found that under the influence of heavy metals under pollution conditions at a depth of 0 - 10 (20) cm, the proportion of absorbing roots of balsamic poplar decreases in comparison with the control. It was revealed that under the conditions of the Sterlitamsk industrial centre, high concentrations of Ni and other metals in soils reduce the supply of Mn to plants. The high content of Ni and other metals in soils under the balsamic poplar stands negatively affects the vital state of trees and leads to a decrease in absorbing roots.

SANITARY AND PROTECTIVE LARIX SUKACZEWII DYL. STAND IN THE POLLUTION CONDITIONS OF THE STERLITAMAK INDUSTRIAL CENTER: STATUS AND PECULIARITIES OF ACCUMULATION OF HEAVY METAL

Introduction. Materials on the distribution of heavy metals in the organs of Larix sukaczewii Dyl are presented in the conditions of the pollution of the industrial center of Sterlitamak. Material and methods. Using the atomic absorption method, the content of copper, lead, and cadmium in the soil cover, needles, branches, and roots was determined in healthy and weakened larch trees. Results. Under conditions of the industrial pollution, the relative life condition of larch stands is estimated as «weakened» (LN = 74.25%), in the control zone as «healthy» (LN = 84.75%). Weakened trees with increasing metal concentrations in soils and roots show an increase in the concentration of metals in the aerial organs, and in healthy trees, it is more deposited in the roots. Discussion. The high content of heavy metals in the soil leads to a redistribution of the root-saturation of the soil with absorbing roots, which is manifested in a decrease in the biomass of the roots in the upper, most contaminated soil layers, and also negatively affects the vital state of the trees by decreasing the density of the tree crown and increasing the share of dead and dying branches on the trunks. Conclusion. Under conditions of contamination, larch is able to actively absorb and deposit a significant amount of Cu, Cd, and Pb, thereby limiting their distribution in the environment.

Evaluation of a Substrate-applied Humectant to Mitigate Drought Stress in Young, Container-grown Plants

The efficacy of treating soilless substrate with a commercial humectant was tested as a means of suppressing drought stress in 4-week-old container-grown Zinnia elegans Jacq. ‘Thumbelina’. The humectant was applied as a substrate amendment at concentrations of 0.0, 0.8, 1.6 and 3.2% by volume prior to withholding irrigation. An untreated, well-watered control was also included. The substrate of treated plants was allowed to dry until the foliage wilted, at which time the plants were harvested and the following measurements taken: number of days to wilt (DTW), xylem water potential (ψx), shoot growth (shoot dry weight, leaf area) and root growth (length, diameter, surface area, volume, dry weight). For drought-stressed plants grown in humectant-treated substrate at concentrations of 1.6 and 3.2%, DTW increased 25 and 33%, respectively. A linear decrease in ψx was observed as the concentration of humectant increased from 0.0 to 3.2%. Linear trends were also noted for both volumetric moisture content (positive) and evapotranspiration (negative) as the concentration of humectant increased. For non-irrigated, untreated plants, stress inhibited shoot growth more than root growth, resulting in a lower root:shoot ratio. For non-irrigated, humectant-treated plants, the length of fine, water-absorbing roots increased linearly as humectant concentration increased from 0.0 to 3.2%. Using humectant-amended substrates may be a management option for mitigating the symptoms of drought stress during the production of container-grown bedding plants such as Z. elegans.

Comparative anatomy of absorbing roots and anchoring roots in three species of Cyclanthaceae (Monocotyledoneae)

Absorbing roots and anchoring roots of Asplundia sp., Evodianthus fiinifer, and Thoracocarpus bissectus differ from one another anatomically in at least 15 quantitative characteristics and in additional related respects. Differences are diverse, involving both stelar and extrastelar tissues. Absorbing roots are significantly greater in diameter, have more vascular tissue, exhibit broader tracheary elements and sieve elements, and have other characteristics supporting the hypothesis that those features logically interpretable as optimizing conduction in xylem and phloem predominate in the absorbing roots. The three species also differ significantly from each other according to the anatomy of their absorbing roots, with T. bissectus having the most distinctive anatomy. Statistical and nonstatistical approaches to analysis of the data provided very consistent results, both in regard to differences between the two root types under study and to differences between taxa. Key words: absorbing roots, anchoring roots, Asplundia, Cyclanthaceae, Evodianthus, root anatomy, Thoracocarpus.

Comparative morphology and anatomy of absorbing roots and anchoring roots in three species of Cyclanthaceae (Monocotyledoneae)

Asplundia sp., Evodianthus funifer, and Thoracocarpus bissectus are root-climbing lianas that each have absorbing roots and anchoring roots. On stems appressed to the trunks of host trees, both types of roots arise mainly from internodes, generally emerging from those halves of stem surfaces facing the trunks (Asplundia sp., E. funifer), and may form nonreplacement roots and replacement roots. Aerial portions of absorbing roots differ from anchoring roots according to direction of growth, abundance of nonreplacement roots, diameter 1 cm distal to base, length, abundance, and color (T. bissectus). In all species the anchoring roots (with or without replacement roots) are interpretable as determinate because on long specimens their distal portions appear anatomically narrowed and reduced. In contrast, aerial parts of absorbing roots are indeterminate. The determinate aspects of anchoring roots and the general restriction (on stems appressed to tree trunks) of roots to trunk-facing stem surfaces are advantageous as means for conserving biomass. Key words: roots, root morphology, root dimorphism, Cyclanthaceae.

INFLUENCES OF SEASONAL TEMPERATURE ON NITROGEN AND SULFUR MINERALIZATION/IMMOBILIZATION IN A MAPLE-BIRCH FOREST FLOOR IN CENTRAL ONTARIO

Net mineralization of sulfur (S) and nitrogen (N) and nitrification in an F(Oe) horizon were examined over a 16-wk period (May to September) with (a) buried bags, (b) lysimeters and (c) closed flasks at 10, 20 or 30 °C. The amount of [Formula: see text] plus [Formula: see text] extracted from soil held at 33 kPa tension over 16 wk, when extrapolated to the mass of soil in the field, was 30 kg ha−1 N and 9 kg ha−1[Formula: see text] at constant 20 °C in the flasks, and 33 kg ha−1 N and 4 kg ha−1[Formula: see text] in buried bags (mean daily temperature 15.2 °C). On the basis of lysimeter data there was a net release of only 8 kg ha−1 N and a net retention of 3 kg ha−1[Formula: see text] under field conditions, with fluctuating temperature and moisture and actively absorbing roots. Nitrate recovered from the three types of experiment was equivalent to 18, 36, and 4 kg ha−1 N, respectively. Mineralization appeared to be particularly sensitive to temporal changes in average daily temperatures in the field. The late-summer peak in mean daily forest-floor temperature triggered a shift from net mineralization to net immobilization of N. Key words: Soil temperature, forest floor, sulfate, ammonium, nitrate

Root systems of older immature hemlock, cedar, and Douglas-fir

Root systems of eight western hemlock (Tsugaheterophylla (Raf.) Sarg.), eight western red cedar (Thujaplicata Donn.), and six Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees, average age about 50 years, average dbh 26.3 cm, were hydraulically excavated. The sizes and shapes of the root systems are given and the root systems and roots are described. Fresh and dry weights of roots of all vegetation averaged 36 and 14 t/ha and were similar for all three species. Fine absorbing roots were distributed mainly in the organic horizon and immediately below it, i.e., in the top 10 or 15 cm of the soil; their turnover appears rapid. Their ovendry weight averaged 210 g/m2 and their length averaged 4 km/m2.

Root System Morphology of Western Hemlock, Western Red Cedar, and Douglas-fir

Root systems of nine western hemlock (Tsugaheterophylla (Raf.) Sarg.), nine western red cedar, (Thujaplicata (Donn), and six Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees were hydraulically excavated in the Cowichan Lake area on Vancouver Island. All three species were similar in depth of root penetration, presence of oblique laterals and sinkers, concentration of rope-like, higher-order laterals, and fine absorbing roots below the organic–mineral interphase, on top of the hardpan and in pockets of organic or fine mineral material. Dominants had proportionally larger and more symmetrical root systems than trees of lower canopies; asymmetry generally increased with increasing stoniness and decreasing soil depth. All three species showed a somewhat greater root development on the downhill side, but exceptions were frequent. Douglas-fir had a larger root spread, roots of larger diameters and smaller taper, and proportionally greater root weight than cedar or hemlock. The density of thin, rope-like roots and absorbing roots was highest on cedar and lowest on Douglas-fir. Hemlock roots followed old decaying roots more frequently than cedar or fir, but root channels were equally used by all species.