Glutamate Dehydrogenase Activity in Roots: Distribution in a Seedling and Storage Root, and the Effects of Red and Far-red Illuminations

Pisum seedling and Pastinaca storage roots contained high glutanrate dehydrogenase (GDH) activity in areas of reported rapid growth and high phytoctrome content. A similar distribution was observed for malate dehydrogenase. Freeze-thawings of mitochondrial preparations from Pisum roots always resulted in increases of GDH specific activity; however, the observed increases were much larger with basal than apical sections. Both intact and freeze-thawed mitochondrial preparations from seedling roots exhibited increases in GDH activity with time after isolation. In intact mitochondrial preparations from roots of etiolated seedlings, an increase in malate dehydrogenase activity was observed similar to that of GDH activity; however, no increased malate dehydrogenase activity was noted in preparations from light-grown seedlings. Illuminating Pisum seedlings with far-red light slowly increased GDH activity in roots over a period of two weeks. Since these observed increases were not due to direct exposure of roots to light, other factors were likely involved.     

The Relationship Between Peroxidase Activity and the Resistance of Tomatoes (Lycopersicum esculentum) to Verticillium dahliae

The levels of peroxidase activity in roots of non-infected tomato plants resistant to Verticillium dahliae Kleb., were found to be considerably higher than those in the roots of susceptible plants. Similar differences were found in the leaves but were not significant as in the roots. Peroxidase activity increased in leaves, stems and roots of both susceptible and resistant plants after infection with V. dahliae. The ratio of the increase in leaves and roots of susceptible plants was greater than those of resistant plants. A positive correlation was found between the peroxidase activity in the roots of eleven cultivars/breeding lines and presence of Ve gene.     

Glutathione reductase activity and isoforms in leaves and roots of wheat plants subjected to cadmium stress

The behavior of glutathione reductase (GR, EC 1.6.4.2) activity and isoforms were analyzed in wheat (Triticum aestivum L.) leaves and roots exposed to a chronic treatment with a toxic cadmium (Cd) concentration. A significant growth inhibition (up to 55%) was found in leaves at 7, 14 and 21 days, whereas roots were affected (51%) only after three weeks. Wheat plants grown in the presence of 100microM Cd showed a time-dependent accumulation of this metal, with Cd concentration being 10-fold higher in roots than in leaves. Nevertheless, lipid peroxidation was augmented in leaves in all experiments, but not in roots until 21 days. Cadmium treatment altered neither the GR activity nor the isoform pattern in the leaves. However, GR activity increased 111% and 200% in roots at 7 and 14 days, respectively, returning to control levels after 21 days. Three GR isoforms were found in roots of control and treated plants, two of which were enhanced by Cd treatment at 7 and 14 days, as assessed by activity staining on native gels. The changes in the isoform pattern modified the global kinetic properties of GR, thereby decreasing significantly (2.5-fold) the Michaelis constant (K(m)) value for oxidized glutathione. Isozyme induction was not associated with an enhancement of GR mRNA and protein expression, indicating that post-translational modification could occur. Our data demonstrated that up-regulation of GR activity by the induction of distinctive isoforms occurs as a defense mechanism against Cd-generated oxidative stress in roots.     

Growth,anatomy and enzyme activity changes in maize roots induced by treatment of seeds with low-temperature plasma

The seeds of Zea mays L. cv. KWS were exposed to low-temperature plasma (LTP) by using Diffuse Coplanar Surface Barrier Discharge (DCSBD) for 60 and 120 seconds respectively. Growth parameters, anatomy of roots and activity of some enzymes (CAT, G-POX, SOD and DHO) isolated from roots grown from the seeds treated by LTP were evaluated. Our results indicate that LTP treatment of maize seeds affects post-germination growth of seedlings and this effect depends on the duration of LTP treatment. LTP treatment in duration of 60 seconds significantly increased the length, fresh and dry weight of the roots. However, the increase in time of LTP treatment to 120 seconds had inhibitive effect on the studied growth parameters. The activities of all studied antioxidant enzymes significantly increased with the age of maize seedlings in control conditions. On the other hand the application of LTP resulted in small, mostly non significant changes in the activity of antioxidant enzymes. Significant decrease in CAT activity was observed both in 3 and 6-day old maize roots and G-POX activity in 3-day old maize roots grown from seeds exposed to LTP for 60 seconds. A small, significant increase was detected only in SOD activity in 3-day old maize roots grown from seeds treated with LTP for 120 seconds and in 6-day old maize roots treated with LTP for 60 seconds. Significantly higher DHO activity was determined in embryos isolated from seeds treated with LTP for 60 seconds. On the contrary, in roots the DHO activity decreased with the time of LTP treatment. LTP treatment of seeds did not affect the anatomy of maize roots and caused only minor changes in the isoenzyme composition of G-POX and SOD.     

Cd induced changes in proline level and peroxidase activity in roots of rice seedlings

The effects of Cd on changes in proline level and peroxidase activity in roots of rice seedlings were investigated. CdCl₂ was effective in inhibiting root growth and in accumulating proline in roots. The inhibition of root growth by Cd is reversible. The reduction of root growth induced by Cd is closely associated with accumulation of proline in roots. External application of proline markedly inhibited root growth of rice seedlings in the absence of Cd. Ionically bound, but not soluble, peroxidase activity in roots was increased by CdCl₂. Proline treatment also resulted in an increase in ionically bound peroxidase activity in roots. The relationship between growth inhibition of roots induced by Cd and changes of proline level and peroxidase activity is discussed.Abbreviations POX peroxidase     

Phenolic composition and biological activities of Tunisian Nigella sativa L. shoots and roots

In the present investigation, methanolic extracts from shoots and roots of Tunisian Nigella sativa were assayed for their antioxidant and antimutagenic activities. The phenolic composition of the methanolic extracts was determined by RP-HPLC. The predominant phenolic compound was vanillic acid with a mean concentration of 143.21 and 89.94 mg per 100 g dry weight of shoots and roots, respectively. Shoots and roots showed comparable and strong superoxide scavenger activity; however, shoots exhibited higher DPPH radical scavenging, reducing and chelating activities than roots. Mutagenic and antimutagenic activities were determined by using the Ames test. Shoots and roots demonstrated important antimutagenic effects. Roots exhibited stronger activity than shoots with an inhibition percentage of 71.32%.     

Immediate acetylene reduction by excised grass roots not previously preincubated at low oxygen tensions

Excised roots of Spartina alterniflora Loisel. and corn reduced acetylene in air without the previously reported period of zero activity lasting 8 to 18 hours. The profiles of acetylene-dependent ethylene accumulation by excised roots and intact plants of S. alterniflora were similar. No significant change in the number of bacteria associated with the roots was detectable during the assay. Most of the nitrogenase activity was detected in the roots and rhizomes of the plants. The salt marsh sediment also was capable of reducing acetylene. Additional damage to roots by washing and cutting increased the rate of acetylene reduction with samples incubated in air. Low concentrations of nitrate significantly inhibited the nitrogenase activity associated with the sediment and excised roots, but not with intact plants. Rates of acetylene reduction by excised corn roots were low. Oxidation and endogenous production of ethylene in the absence of acetylene were negligible. Measurements made with excised grass roots as described probably reflect the occurrence and magnitude of nitrogenase activity associated with the plants in the field.     

Characterization of the antioxidant system during the vegetative development of pea plants

The antioxidative system was studied during the development of pea plants. The reduced glutathione (GSH) content was higher in shoots than in roots, but a greater redox state of glutathione existed in roots compared with shoots, at least after 7 d of growth. The 3-d-old seedlings showed the highest content of oxidised ascorbate (DHA), which correlated with the ascorbate oxidase (AAO) activity. Also, the roots exhibited higher DHA content than shoots, correlated with their higher AAO activity. The activities of antioxidant enzymes were much higher in shoots than in roots. Ascorbate peroxidase (APX) activity decreased during the progression of growth in both shoots and roots, whereas peroxidase (POX) activity strongly increased in roots, reflecting a correlation between POX activity and the enhancement of growth. Catalase activity from shoots reached values nearly 3 or 4-fold higher than in roots. The monodehydroascorbate reductase (MDHAR) activity was higher in young seedlings than in more mature tissues, and in roots a decrease in MDHAR was noticed at the 11^th day. No dehydroascorbate reductase (DHAR) was detected in roots from the pea plants and DHAR values detected in seedlings and in shoots were much lower than those of MDHAR. In shoots, GR decreased with the progression of growth, whereas in roots an increase was seen on the 9^th and 11^th days. Finally, superoxide dismutase (SOD) activity increased in shoots during the progression of growth, but specific SOD activity was higher in roots than in shoots.     

Antioxidant enzymes and isoflavonoids in chilled soybean (Glycine max (L.) Merr.) seedlings

Changes of activity antioxidant enzymes and of levels of isoflavonoids were studied in the roots and hypocotyls of the etiolated soybean (Glycine max (L.) Merr. var. Essor) seedlings, submitted to cold. Prolonged exposure to 1 degrees C inhibited hypocotyl and root elongation and limited their growth after seedlings were transferred to 25 degrees C. Roots were more sensitive to chilling than hypocotyls. At 1 degrees C a gradual increase in MDA concentration in roots but not in hypocotyls was observed. An increase in catalase (CAT, EC 1.11.1.6) and superoxide dismutase (SOD, EC 1.15.1.1) activity in hypocotyls was observed both at 1 degrees C and after transfer of plants to 25 degrees C. In roots, CAT activity increased after 4 days of chilling, while SOD activity only after rewarming. L-Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity decreased in roots of chilled seedlings, but did not change in hypocotyls until activity increased after transfer to 25 degrees C. The content of genistein and daidzein increased after 24 h of treatment by low temperature and then decreased with prolonged chilling in hypocotyls and remained high in roots. However, it should be noted that genistin level (genistein glucoside) in chilled hypocotyls is 10 times higher than in roots, despite falling tendency. The role of antioxidant enzymes and isoflavonoids in preventing chilling injury in hypocotyls and roots of soybean seedlings is discussed.     

Phosphatase activity in corn and soybean roots: Conditions for assay and effects of metals

Studies with sterile root materials showed that the optimum pH values of phosphatase activity in three varieties of each of corn (Zea mays L.) and soybean (Glycine max. L.) were 4 and 5, respectively. The activity on either side of the optimum pH fell sharply, and there was no activity at pH 9. Thus, these roots contain acid but no alkaline phosphatase activity. Acid phosphatase activity was not uniformly distributed in roots and root hairs. Studies with 20 metals showed that their effectiveness in inhibiting acid phosphatase activity of roots varied with the type of plant used. When the metals were compared at 250 μM (1.25 μmole. 5 mg⁻¹ of homogenized roots), the inhibition of acid phosphatase of corn and soybean roots showed that Ag(I), Fe(III), Se(IV), V(IV), As(V) and Mo(VI) were the most effective inhibitors of this enzyme in corn roots, with percentage inhibition ≥30%. In addition to these metals, Sn(II), Hg(II), and W(VI) inhibited acid phosphatase in soybean roots by >30%. Other metals and one non-metallic element that inhibited acid phosphatase activity in corn and soybean roots were: Cu(I), Cu(II), Cd(II), Ni(II), Fe(II), Pb(II), Ba(II), Co(II), Mn(II), Zn(II), B(III), As(III), Cr(III), and Al(III); their degrees of effectiveness varied with type of roots used. Generally, the inhibitory effect of the metals was much less when their concentration was decreased by 10-fold. In addition to the effect of these elements, phosphate ion inhibited acid phosphatase activity of corn and soybean roots. Related anions such as NO ₂ ⁻ , NO ₃ ⁻ , Cl⁻, and SO ₄ ²⁻ were not inhibitory.     

Hypoxia induces anoxia tolerance in roots and shoots of lupine seedlings

Lupine seedlings were exposed to 4 kPa partial pressure oxygen (hypoxically pretreated) for 18 hours before treatment with strictly anaerobic conditions (anoxia). Seedlings previously exposed to hypoxia were more tolerant than the controls (not hypoxically pretreated) to anoxic stress in both roots and shoots. Hypoxic pretreatment induced roots and shoots survival in anoxia. Improved viability of roots, following hypoxic pretreatment, was associated with increased activity of ADH. In nonacclimated roots and shots significant increase in LDH activity occurd during the first hours under anoxia but the in vitro activity of LDH was two orders of magnitude lower than that of ADH. The results are discussed in relation to the ability of lupine seedlings to survive anoxia.     

Non-destructive measurement of acid phosphatase activity in the rhizosphere using nitrocellulose membranes and image analysis

We developed a method using nitrocellulose membranes and image analysis to localise and quantify acid phosphatase activity in the rhizosphere of two plant species, one with cluster roots (Dryandra sessilis (Knight) Domin) and another with ectomycorrhizal roots (Pinus taeda L.). Membranes were placed in contact with roots and then treated with a solution of x, α-naphthyl phosphate and Fast Red TR. Acid phosphatase activity was visualised as a red imprint on the membrane. We quantified acid phosphatase activity by image analysis of scanned imprints. The method was used to estimate the spatial distribution of acid phosphatase activity within particular root classes (lateral roots, mycorrhizal roots, root clusters). Over 95% of the acid phosphatase activity of the root system of D. sessilis was associated with cluster roots, and between 20 and 32% of the root surface active. About 26 % of the acid phosphatase activity of the root system of P. taeda was associated with mycorrhizal roots and unsuberised white root tips and less than 10% of the root surface was active, irrespective of root type. This non-destructive method can be used for rapid, semi-quantitative assessment of acid phosphatase activity in the laboratory and in situ. This revised version was published online in August 2006 with corrections to the Cover Date.     

The regulation of glycolysis and electron transport in roots

The respiration of roots and isolated root mitochondria was investigated in Phaseolus vulgaris L., Spinacea oleracea L.; Triticum aestivum L., and Zea mays L. Although the respiration of both intact roots and isolated mitochondria displayed resistance to cyanide and sensitivity to SHAM, the percentage resistance and inhibition in roots was not the same as that in the mitochondria, with the exception of wheat. Adding FCCP to roots stimulated oxygen uptake and equalized the effects of SHAM and cyanide on roots and mitochondria. In spinach and maize roots, FCCP stimulated both the cytochrome and alternative pathways, while in bean roots, only the alternative pathway was stimulated. FCCP had little effect on wheat root respiration rates. Potential in vivo rates of oxygen uptake were estimated by expressing rates obtained with isolated mitochondria on a fumarase activity basis, and fumarase activity on a root weight basis. In wheat roots the potential rate was approximately equal to the measured in vivo rate; in the other species the potential rates were substantially greater than measured rates, but approximately equal to uncoupled in vivo rates. Key glycolytic intermediates in roots were measured, and it was found that the phosphofructokinase and pyruvate kinase reactions were displaced far from equilibrium, the degree of displacement being approximately equal in roots with little, and roots with substantial, alternative path engagement. Thus, although glycolysis is controlled, the regulation of this pathway appears to be quite flexible. The results are discussed in terms of possible regulatory mechanisms.     

Synergistic effect of auxins and polyamines in hairy roots of <Emphasis Type="Italic">Cichorium intybus</Emphasis> L. during growth,coumarin production and morphogenesis

Hairy roots of Cichorium intybus obtained by infecting with different Agrobacterium rhizogenes strains (LMG-150 and A20/83) were studied for total endogenous indole-3-acetic acid (IAA) levels and indole-3-acetic acid oxidase (IAAO) activity. The roots initiated by LMG- 150 showed higher endogenous IAA levels as well as IAAO activity as compared to the roots from A20/83. Coumarin production in roots obtained by both of these strains strictly correlated with growth, with higher content in the roots obtained by LMG- 150. Moreover roots from LMG-150 showed increased growth index, length of primary roots and number of secondary and tertiary roots. The roots derived from LMG-150 were studied for total endogenous IAA and IAAO activity under the exogenous administration of polyamines and fungal elicitors. The treatment with putrescine (Put) at 1.5 mM level showed maximum endogenous IAA levels and IAAO activity as compared to the control and other polyamine administration, it also supported faster growth in terms of biomass accumulation, and total coumarin production. Of the various treatments, mycelial extract (ME) and culture media filtrate (CMF) of Pythium aphanidermatum and Phytopthora parasitica var. nicotiana, the treatment with 1 % CMF of P. parasitica var. nicotiana, resulted in maximum IAA levels and IAAO activity, which was supported by maximum biomass, coumarin production as compared to the control and other elicitor treatments. Two different regenerants of chicory obtained through A. rhizogenes LMG-150 designated as T-I and T-II, were studied for total endogenous IAA levels and IAAO activity. T-II showed higher titers of IAA with higher activity of IAAO as compared to T-I. Endogenous titer of IAA and IAAO activity was found to be maximum in transformed roots as compared to T-I, T-II, normal roots and normal plants. Our work showed a variation in endogenous auxin levels in these transformed plants. There exists a synergistic effect of endogenous IAA titers and polyamines in regulating root morphogenesis. Fungal elicitors influenced growth and coumarin production and an elicitor preparation of 1 % CMF of P. parasitica var. nicotiana gave spontaneous regeneration of shoots. The implications of these results are discussed.     

A histochemical study of the distribution of choline acetyltransferase and acetylcholinesterase activity in sensory ganglia and nerve roots of the bullfrog

Synopsis Histochemical techniques were employed for the localization of choline acetyltransferase (ChAc; EC 2.3.1.6.), acetylcholinesterase (AChE; EC 3.1.1.7) and cholinesterase (ChE; EC 3.1.1.8) activities in dorsal and ventral roots and dorsal root ganglia of the bullfrog. AChE activity was present in most of the neuronal elements of dorsal root ganglia, in some nerve fibres in the dorsal roots, and in all nerve fibres in ventral roots. ChE activity in dorsal root ganglia and in the dorsal roots was confined to non-neuronal elements. No ChE activity was demonstrable in the ventral roots. ChAc activity was localized in many neurons of the dorsal root ganglia and in some nerve fibres of the dorsal roots; however, none of the ventral root fibres were visibly reactive. Some supportive cells of the dorsal roots and ganglia contained small amounts of ChAc activity. Except for the ventral roots, the histochemical distribution of AChE and ChAc activity was similar. The results of solubility studies indicated that under the histochemical conditions, approximately 50% of the ChAc remained bound to the dorsal roots and ganglia, whereas more than 90% of the ChAc in the ventral roots was soluble. This would account for the lack of reactivity in ventral root fibres. Differences in ChAc solubility are discussed in relation to the interpretation of histochemical data and in relation to the concept of multiple forms of ChAc. The results of this study indicate that at least one-third of the neurons of the dorsal root ganglia contain significant levels of the enzymes involved in both the synthesis and hydrolysis of acetylcholine.     

淹水对甜樱桃根系呼吸强度和呼吸酶活性的影响

以美早/东北山樱桃(Prunus serrulataG.Don)和美早/马哈利(P. mahaleb L.)为试材,研究了淹水对甜樱桃根系（生长根和褐色木质根）呼吸强度和呼吸酶活性的影响.结果表明：淹水过程中,两种甜樱桃砧木生长根和褐色木质根呼吸强度均呈下降趋势,生长根降幅更大;东北山樱桃生长根和褐色木质根呼吸强度降幅分别是马哈利的1.47和1.36倍.丙酮酸脱羧酶(PDC)、乳酸脱氢酶(LDH)活性在两类根系中均呈先升后降趋势,乙醇脱氢酶(ADH)活性在生长根中亦先升后降,而在褐色木质根中为上升趋势,3种酶活性变化幅度表现为生长根大于褐色木质根;东北山樱桃ADH和LDH活性增幅大于马哈利,但PDC活性则相反.两类根系苹果酸脱氢酶(MDH)活性均下降,且生长根降幅大于褐色木质根;东北山樱桃MDH活性降幅大于马哈利.说明生长根对淹水的敏感性强于褐色木质根;与马哈利相比,东北山樱桃对淹水更敏感.     

NaCl-Induced Changes in Putrescine Content and Diamine Oxidase Activity in Roots of Rice Seedlings

The effects of NaCl on putrescine (Put) content and diamine oxidase (DAO) activity in roots of rice seedlings were examined. NaCl treatment lowered the content of Put and increased the activity of DAO in roots. Our current results indicate that Cl^– is not required for NaCl-induced decline in Put content and increase in DAO activity in roots. Put content in roots of rice seedlings exposed to NaCl is possibly regulated by DAO activity.     

Activity and isoenzyme composition of vacuolar peroxidase in the roots of red beet at different stages of development and upon changes in storage conditions

Activity and isoenzyme composition of phenol-dependent vacuolar peroxidase (PO) were examined at different stages of development of red beet (Beta vulgaris L.) roots. The enzyme activity was found to increase during growth and decrease during the period of root dormancy. The isoenzyme composition of PO was also altered; additional cationic and anionic isoforms were revealed at certain stages of growth and dormancy. The dormant roots are often subjected to stresses, such as water deficiency and pathogenesis. For this reason, the enzyme activity in beet roots showing obvious signs of shrivel and infection with pathogenic microorganisms was investigated. The activation of PO was observed in infected roots, whereas the increase in the number of cationic PO isoforms was noted in water-stressed roots. The pH optima of the enzyme were found to shift depending on the developmental stage and the nature of stress factors: during dormancy and under water stress the pH optima shifted towards the acidic values. The shift in pH optima occurred concurrently with the appearance of cationic inducible isoforms. The pH dependences of cationic PO isoforms (these POs were mainly associated with the tonoplast) showed that their activity was optimal at pH 4.0 and 5.0. The observed changes in activity and composition of isoenzymes suggest the active involvement of the vacuolar peroxidase in metabolic processes and cell defense responses in beet roots.     

Induction of Nitrate Reductase and Peroxidase Activity in the Seedlings of Normal and High Lysine Maize

Steady state levels of in vivo nitrate reductase activity in the endosperm, scutella, roots and shoots of maize seedlings were higher in normal maize than those in high lysine maize. Activity of peroxidase in the roots, however, was higher in the high lysine cultivar. The nitrate reductase activity increased with the supply of nitrate in all parts of the seedlings of both cultivars, although the rates of increment in the endosperm were lower than those in scutella, roots and shoots. In relation to substrate concentration, a saturation was achieved at 5 to 10 mM of nitrate except in the endosperm, where activity increased slowly up to 100 mM at least. Final levels of enzyme activity were significantly higher in the scutella of normal than in that of high lysine seedlings. In vitro enzyme activity in the roots also increased with the supply of nitrate in both cultivars, reaching maximum at 5 to 10 mM nitrate.     

Antioxidative responses and proline level in leaves and roots of pea plants subjected to nickel stress

The activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), glutathione S-transferase (GST) as well as proline content were studied in leaves and roots of 14 day-old pea plants treated with NiSO₄ (10, 100, 200 μm) for 1, 3, 6 and 9 days. Exposure of pea plants to nickel (Ni) resulted in the decrease in CuZnSOD as well as total SOD activities in both leaves and roots. The activity of APX in leaves of plants treated with 100 and 200 μm Ni increased following the 3rd day after metal application, while in roots at the end of the experiment the activity of this enzyme was significantly reduced. In both organs CAT activity generally did not change in response to Ni treatment. The activity of GST in plants exposed to high concentrations of Ni increased, more markedly in roots. In both leaves and roots after Ni application accumulation of free proline was observed, but in the case of leaves concentration of this amino acid increased earlier and to a greater extent than in roots. The results indicate that stimulation of GST activity and accumulation of proline in the tissues rather than antioxidative enzymes are involved in response of pea plants to Ni stress.