Changing Root Morphology Research Articles

OsSPL14 is involved in nitrogen-deficiency-induced root elongation in rice

Nitrogen (N) is an essential element for rice (Oryza sativa L.) growth. Rice responds to N-limiting conditions by changing root morphology. Strigolactones (SLs) and auxin modulate rice root elongation under N-deficient conditions. However, the interactions between SLs and auxin in the regulation of root elongation in response to N deficiency remain needing further study. Here, we analysed the function of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 14 (SPL14, a downstream transcription factor of strigolactone signaling) in regulating root elongation under low N (LN) supply. Compared with sufficient N (SN) condition, LN and SN+GR24 (SL analogue) reduced protein interaction between SLs signaling repressor DWARF 53 (D53) and SPL14. The expression of SPL14 was induced by LN supply. In contrasts to WT plants, knockdown of SPL14 resulted in less extensive changes in root length under LN condition. Overexpression of SPL14 under SN supply enhanced root length to the same extent as WT plants under LN condition, suggesting that SPL14 was induced by LN condition and led to changes in root elongation. The transcription of PIN-FORMED 2 and 10b (auxin efflux carriers) were negatively and positively regulated by SPL14, respectively. Under SN and LN conditions, similar root morphology was observed in overexpressing PIN10b and SPL14 lines, and opposite root phenotypes were recorded between pin2 mutants and SPL14-RNAi lines.These results indicated that PIN2 and PIN10b were involved in SPL14-induced root elongation under LN condition. Therefore, we presented that, LN inhibits D53 and SPL14 interaction, which releases SPL14 to modulate the transcription of PIN2 and PIN10b, resulting in root elongation in rice.

Effects of nitrogen fertilizer rates on the growth and nutrient utilization of calla lily intercropped with rubber trees

Rubber tree (Heveabrasiliensis Müll. Arg.)–calla lily (Alocasiamacrorrhizos L.) intercropping, practiced in Hainan, China, is a new and promising intercropping system suitable for implementation in shaded mature rubber plantations of which the main product is industrial starch. Nutrient competition between rubber trees and calla lilies was significant in this intercropping system, with rubber trees holding a competitive advantage. In addition, nitrogen (N) fertilizer is commonly used in excess in China. Therefore, adequate N supply is the basis of rubber tree–calla lily intercropping systems that reduces inter-species N competition and ensures efficient intercropping. In this study, experiments with monocropping and intercropping systems under five different N application concentrations (0, 100, 200, 300, and 400 kg ha−1) were conducted to assess how the interaction between intercropping and N fertilizer application rates affected the growth, development, distribution of biomass, and nutrient uptake and utilization in calla lilies, using the root barrier method. The results showed that only when the N fertilizer rates were < 200 kg ha−1, intercropping significantly inhibited calla lily growth and development, but significantly increased the number and length of calla lily roots, and allocated more dry matter to the roots. however, intercropping promoted calla lily growth and development at a N fertilizer application rate of 400 kg ha−1. Intercropping increased the phosphorus (P) concentration and decreased the N and potassium (K) concentrations, and lower N fertilizer rates resulted in larger increases in the P concentration. Intercropping decreased N utilization efficiency in calla lilies, whereas adequate N fertilizer increased N utilization efficiency. These results indicated that calla lilies adapted to the intercropping and low N fertilizer rates condition by balancing growth, changing root morphology, and reserving nutrients in roots, and shows that scientific and rational fertilization application rates can eliminate the negative effects caused by intercropping due to nutrient competition. For the long-term success of intercropping calla lily in mature rubber plantations, N fertilizer must be applied to mitigate the adverse effects of interspecific competition. Based on the growth and N utilization efficiency of calla lilies in relation to N input costs, the optimal N fertilizer rate in rubber tree–calla lily intercropping systems is 200 kg ha−1.

The physiological mechanism underlying root elongation in response to nitrogen deficiency in crop plants.

In response to low nitrogen stress, multiple hormones together with nitric oxide signaling pathways work synergistically and antagonistically in crop root elongation. Changing root morphology allows plants to adapt to soil nutrient availability. Nitrogen is the most important essential nutrient for plant growth. An important adaptive strategy for crops responding to nitrogen deficiency is root elongation, thereby accessing increased soil space and nitrogen resources. Multiple signaling pathways are involved in this regulatory network, working together to fine-tune root elongation in response to soil nitrogen availability. Based on existing research, we propose a model to explain how different signaling pathways interact to regulate root elongation in response to low nitrogen stress. In response to a low shoot nitrogen status signal, auxin transport from the shoot to the root increases. High auxin levels in the root tip stimulate the production of nitric oxide, which promotes the synthesis of strigolactones to accelerate cell division. In this process, cytokinin, ethylene, and abscisic acid play an antagonistic role, while brassinosteroids and auxin play a synergistic role in regulating root elongation. Further study is required to identify the QTLs, genes, and favorable alleles which control the root elongation response to low nitrogen stress in crops.

Nitrogen form regulates cadmium uptake and accumulation in Tanzania guinea grass used for phytoextraction

Plants benefit from the simultaneous uptake of nitrate (NO3−) and ammonium (NH4+), which can influence the bioaccumulation of heavy metals. Nevertheless, there are no studies on the effect of nitrogen forms on grasses used for cadmium (Cd) phytoextraction. The objective was to evaluate the response of Panicum maximum cv. Tanzania to NO3−/NH4+ ratios and Cd levels. A 3 × 3 factorial experiment was conducted under greenhouse conditions, in a randomized complete block design replicated three times, with three NO3−/NH4+ ratios (100/0, 70/30 and 50/50) and three Cd levels (0.0, 0.5 and 1.0 mM). Although it increased plant total nitrogen concentration, Cd exposure reduced shoot and root growth. Moreover, it altered nitrogen metabolism and induced the accumulation of NO3− and NH4+ mainly in shoots. The supply of 50/50 disturbed glutamine synthetase activity and changed root morphology under Cd toxicity. However, while the exclusive use of NO3− mitigated toxicity symptoms, by favoring Cd accumulation in roots and maintaining normal nitrogen metabolism, plants grown with 50/50 showed increased uptake, transport and accumulation of this metal. Thus, Cd uptake and accumulation are strongly related to the form of nitrogen available, and the supply of 50/50 increases the phytoextraction of this metal.

Effect of phosphate solubilising bacteria (Enterobacter cloacae) on phosphorus uptake efficiency in sugarcane (Saccharum officinarum L.)

Phosphorus (P) is an essential nutrient in sustainable production of sugarcane. Due to low labile P in soil under sugarcane cultivation, evaluation of the efficiency of P uptake and the application of phosphate solubilising bacteria (PSB) play important roles in management of P fertiliser. To investigate the effect of using PSB on P uptake in sugarcane (variety CP57–614), a pot experiment was conducted with three replications in greenhouse conditions. The treatments were a combination of three P rates (0 (P0), 50 and 100% (~40 mg kg−1) as triple superphosphate, and two PSB strains (Enterobacter cloacae R13 (R13) and R33 (R33)) which were applied independently and simultaneously. Morphological characteristics of sugarcane and some biochemical parameters were evaluated in the rhizosphere at three harvesting times: 60, 95 and 140 days after planting (DAP). Whereas in low available P (P0), bacterial strain R33 improved P uptake along with sugarcane ageing, P uptake was diminished in non-inoculated treatment over time. Activity of PSBs in the rhizosphere (especially strain R33) prevented the sharp fall of P influx after 95 DAP in low available P condition. Indeed, activity of R33 in the rhizosphere decreased the dependence of P uptake on root development via improving P uptake. Therefore, influx was the main mechanism of P uptake in sugarcane. Sugarcane inoculated by PSBs acquired 76 and 81% of total P uptake from non-Olsen-P fraction in P0R13 and P0R33 respectively at 95 DAP. However, this amount was lower (70.4%) in P0R0. Furthermore, strain R33 improved P uptake efficiency in sugarcane by changing root morphology (e.g. specific root length and root length) and reducing soil limitations (e.g. enhancement of P compound solubility and P influx).

Nitric Oxide Affects Rice Root Growth by Regulating Auxin Transport Under Nitrate Supply.

Nitrogen (N) is a major essential nutrient for plant growth, and rice is an important food crop globally. Although ammonium (NH4+) is the main N source for rice, nitrate (NO3-) is also absorbed and utilized. Rice responds to NO3- supply by changing root morphology. However, the mechanisms of rice root growth and formation under NO3- supply are unclear. Nitric oxide (NO) and auxin are important regulators of root growth and development under NO3- supply. How the interactions between NO and auxin in regulating root growth in response to NO3- are unknown. In this study, the levels of indole-3-acetic acid (IAA) and NO in roots, and the responses of lateral roots (LRs) and seminal roots (SRs) to NH4+ and NO3-, were investigated using wild-type (WT) rice, as well as osnia2 and ospin1b mutants. NO3- supply promoted LR formation and SR elongation. The effects of NO donor and NO inhibitor/scavenger supply on NO levels and the root morphology of WT and nia2 mutants under NH4+ or NO3- suggest that NO3--induced NO is generated by the nitrate reductase (NR) pathway rather than the NO synthase (NOS)-like pathway. IAA levels, [3H] IAA transport, and PIN gene expression in roots were enhanced under NO3- relative to NH4+ supply. These results suggest that NO3- regulates auxin transport in roots. Application of SNP under NH4+ supply, or of cPTIO under NO3- supply, resulted in auxin levels in roots similar to those under NO3- and NH4+ supply, respectively. Compared to WT, the roots of the ospin1b mutant had lower auxin levels, fewer LRs, and shorter SRs. Thus, NO affects root growth by regulating auxin transport in response to NO3-. Overall, our findings suggest that NO3- influences LR formation and SR elongation by regulating auxin transport via a mechanism involving NO.

Mapping the footprint of nematodes in the rhizosphere: Cluster root formation and spatial distribution of enzyme activities

Nematodes are among the most important pathogens in agriculture, greatly reducing crop biomass and yield. The direct effects of nematodes on above– and belowground plant parts are well known, but the broad range of indirect effects, especially on carbon (C) and phosphorus (P) cycles underground, remains unknown. For the first time, using soil zymography, we analyzed the indirect effects of Meloidogyne incognita cellobiohydrolase and phosphatase. The rhizosphere of lupine (Lupinus polyphyllus L.), a species sensitive to pathogens with high P demand, was selected to study the activity, distribution and localization of two enzymes responsible for C and P cycling: The distribution patterns of cellobiohydrolase and phosphatase demonstrated that M. incognita induced the formation of knots as well as cluster roots, which corresponded to hotspot locations on zymogram images for both enzymes. Increased C release by nematode–infected roots into the soil led to a decrease in the overall activity of cellobiohydrolase and especially at hotspots (by ∼ 20 times). In contrast, the increased P demand of infected plants raised the phosphatase activity, leading to an increase in the rhizosphere extent around the roots and especially of the hotspot area (by 6 times). Remarkably, this 1 mm increase of rhizosphere extent in 2D equals a 2-fold increment in soil volume (3D) for nutrient mobilization.We conclude that nematode infection not only has direct effects by changing root morphology, but also induces a number of subsequent biochemical changes (e.g. enzyme activities and consequently nutrient mobilization) in the rhizosphere, affecting C and P cycling.

Effects of transgenic soybean on growth and phosphorus acquisition in mixed culture system.

Transgenic soybean plants overexpressing the Arabidopsis purple acid phosphatase gene AtPAP15 (OXp) or the soybean expansin gene GmEXPB2 (OXe) can improve phosphorous (P) efficiency in pure culture by increasing Apase secretion or changing root morphology. In this study, soybean-soybean mixed cultures were employed to illuminate P acquisition among plants in mixed stands of transgenic and wild-type soybean. Our results showed that transgenic soybean plants were much more competitive, and had greater growth and P uptake than wild-type soybean in mixed culture in both low P calcareous and acid soils. Furthermore, OXe plants had an advantage in calcareous soils when mixed with OXp, whereas the latter performed much better in acid soils. In soybean-maize mixed culture, transgenic soybean had no impact on maize growth compared to controls in both acid and calcareous soils with different P conditions. As for soybean in mixed culture, OXp plants had no significant advantages regardless of P availability or soil type, while P efficiency improved in OXe in calcareous soils compared to controls. These results imply that physiological traits could be easily affected by the mixed maize. Transgenic soybean plants with enhanced root traits had more competitive advantages than those with improved root physiology in mixed culture.

오옥신 처리가 에키네시아의 부정근 및 생리활성물질 생산에 미치는 영향

The production of adventitious roots derived from root explant of Echinacea angustifolia and its secondary metabolite content were assessed in different types and levels of auxin. The induction of adventitious roots from root explant cultured in Murashige and Skoog solid medium supplemented with 1.0 ㎎/L indole -3-butyric acid (IBA) attained highest as 20.87 ㎎ fresh weight and 3.07 ㎎ dry weight per culture but root suspension culture at the same concentration of IBA enhanced biomass production as 3.07 g fresh weight and 0.38 g per culture after 4 weeks in culture. 3.0 ㎎/L α-naphthalene acetic acid (NAA) treatment had similar effect on root biomass production as 3.07 g fresh weight and 0.38 g per culture with liquid suspension culture, whereas adventitious roots exposed to over 3.0-5.0 ㎎/L IBA or 5.0 ㎎/L NAA were less responsive by reducing the number of adventitious roots and/or changing root morphology such as short and thick. The content of secondary metabolites such as phenolic, flavonoids and total caffeic acid in adventitious roots cultured on MS medium supplemented with 1.0 ㎎/L IBA were attained highest as 27.20, 9.60. 10.67 ㎎/g dry weight, respectively. Overall, the best production of root biomass and secondary metabolites were given by 1.0 ㎎/L IBA.

Influence of arbuscular mycorrhizae on biomass and root morphology of selected strawberry cultivars under salt stress

To investigate the influence of arbuscular mycorrhizal fungi (AMF) on biomass and root morphology, a greenhouse experiment was conducted using three elite strawberry ( Fragaria × ananassa Duch.) cultivars (‘Kent’, ‘Jewel’, and ‘Saint-Pierre’). They were subjected to three NaCl levels (0, 30, and 60 mmol/L) and were inoculated and noninoculated (control) with AMF Glomus irregulare . The presence of AMF significantly changed root morphology and increased root-length percentages of medium (0.5 mm &lt; root diameter φ ≤ 1.5 mm) and coarse (φ &gt; 1.5 mm) roots, shoot and root tissue biomass, root to shoot ratio (R/S ratio), and specific root length (SRL), regardless of cultivar and salinity. In contrast, salt alone changed root morphology and decreased shoot and root tissue biomass, R/S ratio, and SRL. The AMF colonization rates were reduced linearly and significantly with increasing salinity levels. Cultivars responded differently to AMF than to salt stress. ‘Saint-Pierre’ seemed to be the most tolerant cultivar to salinity, while ‘Kent’ was the most sensitive. Consequently, AMF symbiosis highly enhanced salt tolerance of strawberry plants, which confirmed the potential use of mycorrhizal biotechnology in sustainable horticulture in arid areas.

Growth, root colonization and nutrient status of Helianthemum sessiliflorum Desf. inoculated with a desert truffle Terfezia boudieri Chatin

This study aims to investigate the effects of inoculation using Terfezia boudieri Chatin ascospores (ectomycorrhizal fungus) on growth, root colonization and nutrient status of Helianthemum sessiliflorum Desf. seedlings grown in pots on two-soil types (gypseous and sandy loam). Mycorrhizal seedlings had significantly increased their height and leaf number compared to non-mycorrhizal ones. Regardless of mycorrhizal inoculation treatments, the plants growing on gypseous soil showed higher growth as compared to sandy loam one. It appears that inoculation with T. boudieri changed root morphology, increasing branching of first-order lateral roots of H. sessiliflorum seedlings. The highest root mycorrhizal colonization was recorded in inoculated seedlings on sandy loam soil (89%) when compared to gypseous one (52%). N, P and K concentrations in mycorrhizal seedlings were significantly improved by fungal inoculation. It can be concluded that inoculation of H. sessiliflorum with T. boudieri increased growth attributes and improved plant nutritional status.

Effect of Tree Size, Root Pruning, and Production Method on Root Growth and Lateral Stability of Quercus virginiana

This research aimed to evaluate impact of slicing the outer edge of container root balls, initial tree size at planting, and root ball composition on post-planting tree stability in a simulated wind storm. One-hundred twenty Cathedral Oak® live oak were planted in March 2005. Thirty field-grown trees were transplanted, and 60 trees of similar size were planted from 170 L containers. Root ball sides on 30 containers were sliced prior to planting. Thirty smaller trees from 57 L containers were planted without slicing. Trees were pulled with an electric winch, and blown with a hurricane simulator in 2007. Slicing the root ball had no impact on root growth, bending moment, or bending stress. More bending stress was required to pull field-grown trees than trees planted from containers of either size. Growing trees in containers for three years prior to landscape planting changed root morphology compared to field-grown trees, which corresponded to reduced stability. Trees planted from small containers were as stable as those from larger containers. Root cross-sectional area windward correlated the most with bending stress required to tilt trees with a winch and cable. Bending moment scaled to the 3.4 power of trunk diameter.

Dry mass partitioning and nitrogen uptake by Eucalyptus grandis plants in response to localized or mixed application of phosphorus

Plants respond to nutrient rich patches by changing root morphology and physiology. The aim of this paper was to analyze shoot and root growth of Eucalyptus grandis plants fertilized with the same amount of phosphorus applied in two different ways: thoroughly mixed in the soil or localized in a single hole near the plant. Localized fertilization increased root mass in the zone where fertilizer was applied, but total root mass was not altered by the type of fertilization application. With mixed fertilization plant growth was less than with localized fertilization, and plants showed nitrogen deficiency. Nitrogen uptake was measured in a split-root hydroponics system where phosphate was applied to the whole root system or in part of it. Growth of plants receiving phosphorus in the whole root system was limited by nitrogen uptake, as was revealed by low leaf N and low nitrate uptake. In conclusion, the positive effect of localized application of phosphorus must be ascribed not only to higher phosphorus but also to sustained nitrogen assimilation.

Paxillus involutus Forms an Ectomycorrhizal Symbiosis and Enhances Survival of PtCOMT-modified Betula pendula in vitro

AbstractThe ability of the PtCOMT (caffeate/5-hydroxyferulate O-methyltransferase from Populus tremuloides L.) - modified Betula pendula Roth. lines to form symbiosis with an ectomycorrhizal (ECM) fungus Paxillus involutus Batsch Fr. was studied in vitro. Lignin precursor gene PtCOMT was introduced into two B. pendula clones under the control of the cauliflower mosaic virus 35S promoter or the promoter of the sunflower polyubiquitin gene UbB1. Of the four transgenic lines, one 35SPtCOMT line (23) had a decreased syringyl/guaiacyl (S/G) ratio of root lignin, and two UbB1-PtCOMT lines (110 and 130) retarded root growth compared to the control clone. Both control clones and all transgenic lines were able to form ECMs with P. involutus, but the transgenic lines differed from the controls in the characteristics of the ECMs. The number of lateral roots covered with fungal hyphae and/or development of a Hartig net (HN) were reduced in line 23 with a decreased S/G ratio, and in lines 110 and 130 with slower root formation and changed root morphology, respectively. However, line 23 benefited more from the inoculation in lateral root formation than the control, and in lines 110 and 130 the percentage of viable plants increased most due to inoculation. The results show that B. pendula plants genetically transformed with the lignin gene PtCOMT could form mycorrhizal symbiosis regardless of changes in either the root S/G ratio or development. The benefits of the symbiosis were variable even in the closed in vitro system, and dependent on the clone or transgenic line and the ECM fungal symbiont.

Genetic Dissection of Hormonal Responses in the Roots of Arabidopsis Grown under Continuous Mechanical Impedance

We investigated the role of ethylene and auxin in regulating the growth and morphology of roots during mechanical impedance by developing a new growing system and using the model plant Arabidopsis (Arabidopsis thaliana). The Arabidopsis seedlings grown horizontally on a dialysis membrane-covered agar plate encountered adequate mechanical impedance as the roots showed characteristic ethylene phenotypes: 2-fold reduction in root growth, increase in root diameter, decrease in cell elongation, and ectopic root hair formation. The root phenotype characterization of various mutants having altered response to ethylene biosynthesis or signaling, the effect of ethylene inhibitors on mechanically impeded roots, and transcription profiling of the ethylene-responsive genes led us to conclude that enhanced ethylene response plays a primary role in changing root morphology and development during mechanical impedance. Further, the differential sensitivity of horizontally and vertically grown roots toward exogenous ethylene suggested that ethylene signaling plays a critical role in enhancing the ethylene response. We subsequently demonstrated that the enhanced ethylene response also affects the auxin response in roots. Taken together, our results provide a new insight into the role of ethylene in changing root morphology during mechanical impedance.

Interaction Between Iron Stress and Root-Zone Temperature on Physiological Aspects of Aeroponically Grown Chinese Broccoli

ABSTRACT Chinese broccoli (B. alboglabra), a subtropical vegetable was first grown at 25°C root-zone temperature (RZT) while its aerial portions were exposed to the hot, fluctuating temperatures for four weeks in the tropical greenhouse. Interaction between iron (Fe) stress and RZT were then studied by exposing the plant roots to 2 different RZTs: a constant cool 25°C-RZT (CRZT) and a fluctuating hot ambient RZT (ARZT). There were three different Fe levels [full Fe (FFe), 1/2Fe, and 0Fe] in the nutrient medium supplied to plants at each RZT. Compared to plant grown at CRZT, hot ARZT resulted in decreases in shoot and root productivities, photosynthetic CO2 assimilation rate (A), stomatal conductance (g s ), Fe and nitrate (NO3 −) uptake and transport and nitrate reductase activity (NRA). Hot ARZT also altered root morphology. Iron stress (1/2Fe and 0Fe) caused significant reductions in all the above parameters and changed root morphology when plants were grown at CRZT compared to those grown at FFe. However, most of the parameters studied had similar values at ARZT regardless of Fe levels. These results indicate that hot ARZT may mask the effects of Fe stress on certain physiological process which was clearly elucidated at RZT.

Effects of Mycorrhizal Inoculation on Root Morphology and Nursery Production of Three Grapevine Rootstocks

Grapevines form mutualistic symbioses with arbuscular mycorrhizal (AM) fungi that have been shown to enhance plant growth and nutrition. In the field, AM fungal populations may be low or nonexistent (in fumigated soils), suggesting the need for AM inoculation of grapevine plants at the nursery. Addition of AM fungal inoculum to rooting substrate could be an effective strategy for the nursery production of mycorrhizal plants. The effects of inoculation of three grapevine rootstocks on root morphology and growth were tested. Results indicated that inoculation with the AM fungus <i>Glomus aggregatum</i> in rooting beds of grapevine cuttings changed root morphology, increasing branching of first-order lateral roots. When rooted cuttings were transplanted to pots, with soil sufficient in P and including indigenous AM fungi, and grown for nine months, a significant growth enhancement was found in two of the inoculated rootstocks. <i>Glomus aggregatum</i>, alone or in synergy with the indigenous AM fungi, seemed to have a higher affinity for 161-49 Couderc, the roots of which were more extensively colonized and exhibited a greater positive growth response.

Production of volatile compounds by hairy root cultures of Cichorium intybus L under the influence of fungal elicitors and their analysis using solid‐phase micro extraction gas chromatography–mass spectrometry

AbstractHairy root cultures of Cichorium intybus L produced volatile aromatic compounds under the influence of fungal elicitors. It was observed that the intensity of the production of volatile aromatic compounds in the hairy root cultures of C intybus with 10 ml l−1 media filtrate (MF) of Phytopthora parasitica var nicotiana reached a maximum on the 21st day, as seen by a quantitative flavour profiling method. It was noted that, during the time course, treatment with 10 ml l−1 MF of P parasitica to the MS basal liquid medium containing hairy root cultures of chicory resulted in changed root morphology with cell wall thickening and shear. The components of the volatile aromatic compounds were identified as a propyl isovalerate, undecanal, nonanol, isoamyl nonanoate and 2‐decene‐1‐ol. The mass spectra of all these compounds matched well with the NIST/EPA/NIH library and by comparing with the Kovats index of volatile compounds. The major fruity note was due to the presence of two of the major volatile components, namely propyl isovalerate and isoamyl nonanoate, which were also produced at higher concentration on day 21. This response of chicory hairy root cultures to the fungal elicitor producing volatile aromatic compounds would imply eco‐physiological functions, possibly for plant defence system. Copyright © 2003 Society of Chemical Industry

Collection of Arabidopsis thaliana mutants with altered sensitivity to oxidative stress inductors

Selective systems for screening Arabidopsis thaliana (L.) Heynh. mutants with altered sensitivity to the oxidative stress (OS) inductors norflurazon (NF), acifluorfen (AF), and plumbagin (PB) were developed and a collection of 28 mutants was obtained. Dwarf and necrotic forms predominated among the NF-tolerant mutants, while pigment mutants and those with changed root morphology prevailed among the AF-tolerant and PB-sensitive mutants, respectively. Genetic and biochemical analysis of certain mutants was performed; quantitative and qualitative changes in the content of superoxide dismutase and peroxidase isoforms have been revealed. These data, complemented by the data on the cross-tolerance (sensitivity) of the mutants to paraquat, indicate a correlation between tolerance to the OS inductors and the functions of antioxidant systems.

Changes in Interior Douglas-Fir Root Development in Containers after Copper and Auxin Treatments

Abstract Growing interior sources of Douglas-fir (Pseudotsuga menziesii var. glauca) seedlings in containers with four root-modifying treatments changed root morphology and subsequent abundance and location of new roots. Copper, 1-napthaleneacetic acid (NAA), and copper + NAA treatments reduced height and shoot biomass about 20% compared with the control, but root collar diameters were similar. In a root growth chamber, however, 30% more new roots occurred in the copper treatment compared with the control, and new roots originating in the upper portion of the root plug increased 3X. NAA increased the total number of new roots and roots growing from the upper root plug when compared with the control but not to the same extent as copper. Combining copper and NAA decreased the number of deliverable seedlings by about 50% when compared with all other treatments. West. J. Appl. For. 15(4):213–216.