Diltiazem influence on calcium and aluminum absorption by roots of three sorghum cultivars

Calcium (Ca⁺⁺) (10 mM) and Al⁺⁺⁺ (10 mM) ions were applied unilaterally in agar to primary roots of sorghum [Sorghum bicolor (L.) Moench.]. Both Ca⁺⁺ and Al⁺⁺⁺ caused unilateral growth “inhibitions and induced root curvature in cv Funk G522DR, SC574, and SC283 (acid soil stress sensitive, tolerant, and tolerant, respectively). Diltiazem (0.1 mM) [3‐(acetyloxy)‐5‐[2‐(dimethylamino)ethyl]‐2,3‐dihydro‐2‐(4‐methoxyphenyl)‐l‐5‐benzothiozepin‐4 (5H)‐one] inhibited Ca⁺⁺ absorption in Funk G522DR and SC283 but only partially influenced Ca⁺⁺ absorption by roots of SC574. Aluminum ion absorption by roots was inhibited in SC283 and SC574 but not in Funk G522DR.     

Nifedipine influence on mineral nutrient uptake by sorghum primary root tips

Seedling sorghum [Sorghum bicolor (L.) Moench. cv GP‐10, SC283, SC574, and Funk G522DR] primary root tips (1‐cm) content of calcium (Ca), phosphorus (P), zinc (Zn), boron (B), manganese (Mn), iron (Fe), magnesium (Mg), and copper (Cu) in response to a Ca²⁺‐channel blocker (nifedipine 0, 0.01, 0.1, or 1 μM) was measured after a 1‐hr exposure to Hoagland and Arnon complete mineral nutrient solution. Content of ions was significantly different among the cultivars. Responses to nifedipine were element‐cultivar‐blocker concentration dependent.     

Calcium (45CA2+) absorption by sorghum seedling roots after exposure to PCMBS and three cation channel blockers

Root‐tips, 1‐cm, of Sorghum bicolor (L.) Moench cv SC283, SC574, GP‐10, and Funk G522DR were exposed to 1 mM PCMBS for 10‐min and then to ⁴⁵Ca²⁺ in the presence of cation channel blockers nifedipine (0, 0.001, 0.01, 0.1, or 1.0 μM), diltiazem (0, 0.001, 0.01, 0.1, 1.0, or 10.0 mM), or verapamil (0, 0.01, 0.1, 1.0, or 10.0 mM)] at pH 5.5 for 2‐hr. Significant differences in total ⁴⁵Ca²⁺ absorption between cultivars without cation channel‐blockers was observed. Each channel‐blocker was effective at concentrations that were interactions of channel‐blocker and cultivar.     

Sorghum cultivar variation in Ca2+ and aluminum influence on root curvature

Calcium (Ca²⁺) and aluminum induced unilateral root growth inhibitions (i.e. root curvature) when applied in agar to one side of sorghum [Sorghum bicolor (L.) Moench] roots. PCMBS (p‐chloromercuribenzenesulfonic acid) (10 mM) stopped the root growth inhibition (i.e. curvature) by aluminum in SC574 and SC283 (acid‐soil‐stress tolerant cultivars) but not in Funk G522DR (acid‐soil‐stress sensitive). PCMBS influenced Ca²⁺‐induced root growth inhibition (i.e. curvature) in Funk G522DR and SC283, but not in SC574.     

NonEDTA extractable Scandium in roots of three sorghum cultivars

Scandium (Sc³⁺) is a rare earth whose uptake and physiological function mimics Al³⁺. In sorghum [Sorghum bicolor (L.) Moench.] root tips (1 cm), nonextractable (water and EDTA (15 mM)] Sc³⁺ (1 mM) increased as the pH of the growing medium decreased (pH 6.0 . pH 4.0) in Funk G522DR (an add soil stress sensitive cultivar). Nonextractable Sc³⁺ did not increase in root tips of the two acid soil stress tolerant cultivars SC574 and SC283. Water extractable Sc³⁺ varied by genotype and was SC 283 ≥ SC574 > Funk G522DR. These short term (10 min) sorption studies show a major pH influence on Sc³⁺ content of Funk G522DR, but not in SC283 and SC574 that cannot be due to mucigel contents.     

Malachite green influence on calcium (45Ca2+) absorption by sorghum root tips

Malachite green (MG) [N‐[4‐[[4‐dimethylamino)phenyl] phenyl‐methylene]‐2,5‐cyclohexadien‐l‐yl idene] ‐N‐methyl‐methanarninium chloride] (0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0 mM) was evaluated for influence on calcium (⁴⁵Ca²⁺) absorption by 1‐cm root‐tips of sorghum [Sorghum bicolor (L.) Moench. cv GP‐10, SC283, SC574, and Funk G522DR]. Calcium (⁴⁵Ca²⁺) absorption was significantly decreased in all four cultivars at 0.1 mM. LD₅₀’s were Funk G522DR (0.15 mM), GP10 (0.25 mM), SC283 (0.30 mM), and SC574 (0.31 mM).     

Erythrosine B influence on sorghum root curvature and wheat leaf rust germling use of extracellular lipids

Root curvature response to unilaterally applied calcium (Ca²⁺) in agar was inhibited 81% by erythrosine B (EB) (10 nM) in sorghum [Sorghum bicolor (L.) Moench.] cv Funk G522DR, 70% in cv SC283, and 11% in cv SC574. EB (10 nM) is reported to totally inhibit Ca²⁺‐ATPase, while 10–50 μM EB is required to inhibit H⁺‐ATPase. Therefore, differences in relative concentrations of Ca²⁺‐ATPase and H+‐ATPase exist in the root plasma membranes (PM) of the three cultivars. Carbon dioxide (¹⁴CO₂) production from glycerol‐tri‐(1‐¹⁴C)‐palmitate by wheat (Triticum aestivum L.) leaf rust (Puccinia recondita Rob. ex Desm.) urediospore germlings was inhibited 85% by EB (10 nM).     

H+‐atpase and H+‐transport activities in tonoplast vesicles from barley roots under salt stress and influence of calcium and abscisic acid 1

Seedlings of two barley cultivars differing in NaCl sensitivity were treated with low (100 mM) or high (400 mM) concentration of NaCl for 6 days. Tonoplast vesicles were prepared from roots, and H⁺‐ATPase and H⁺‐transport activities associated with tonoplast were assayed. Both H⁺‐ATPase and H⁺‐transport activities in the two cultivars were increased at 100 mM NaCl. These activities also increased in the salt‐tolerant cultivar at 400 mM NaCl, but in salt‐sensitive cultivar were decreased. In vivo treatment with 10 mM Ca²⁺ stimulated H⁺‐ATPase and H⁺‐transport activities at two levels of NaCl, however, treatment with 10⁵M (±) abscisic acid (ABA) inhibited these activities. From these results we propose that the increase of the vacuolar H⁺ pumps in barley roots reflects an adaptation to salt stress. The stimulation of HVATPase and H⁺‐transport activities by calcium (Ca) depends mainly on its effect in maintaining stability of membrane under salt stress.     

Interactions of metolachlor and excess hydrogen (H+) influences on sorghum (sorghum bicolor) cultivar roots

Sorghum [Sorghum bicolor (L.) Moench] cultivars were planted in 8 cm × 8 cm × 8 cm pots filled with ‘white quartz flintshot’ sand containing 0, 0.25, 0.50, 1.0, or 2.0 mg/kg metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2 methoxy‐1‐methylethyl)acetamide] and the pots were watered on alternate days with 100 mL 0.1 M sodium acetate at pH 6.0, 5.5, 5.0, 4.5, or 4.0 to determine the influence of excess H⁺ and metolachlor concentrations on sorghum root growth. Cultivars utilized were Funk G522DR, SC574, SC283, GP‐10, 58M, and 38M. At pH 4.5 and 4.0 (0 metolachlor), root lengths of Funk G522DR and SC574 were significantly decreased compared to roots from plants grown at pH 6.0. The other four cultivars had decreased root growth at pH 4.0 (0 metolachlor). Metolachlor influence on sorghum cultivar root growth was dependent on pH, cultivar, and metolachlor concentration. None of the cultivars showed increased metolachlor activity which was influenced by pH. Metolachlor (0.25 mg/kg) reversed the influence of excess H⁺ concentration (pH 4.0) in SC574. Metolachlor (0.5, 1.0, and 2.0 ppmw) reversed the excess H⁺ concentration inhibition of root growth at pH 4.0 in Funk G522DR.     

Element absorption by sorghum root tips as influenced by multiple ion‐channel and ion‐pump inhibitors

Mineral nutrient absorption by 1‐cm root tips of Sorghum bicolor (L.) Moench. cv GP‐10, SC283, SC574, and/or Funk GS22DR from a 1‐hr exposure to Hoagland and Arnon complete mineral nutrient solution in the presence of diltiazem (0,10 mM), nifedipine (0,10 mM), or SITS (0, 1 mM) was evaluated using inductively coupled plasma emission photometry (ICP). Calcium (Ca²⁺) ‐ channel blockers (i.e. ‐ diltiazem, nifedipine, and verapamil) and PCMBS induced significantly decreased quantities of Ca²⁺ in root tips but the anion channel blocker, SITS, did not induce any response in Ca²⁺ uptake. Responses of phosphorus (P), zinc (Zn), boron (B), manganese (Mn), iron (Fe), magnesium (Mg), and copper (Cu) to all of the ion uptake modifiers were highly variable between the cultivars with increased, decreased, or no influence on ion uptake. As yet unrecognized multiple mechanisms of ion uptake through the root plasma membrane are necessary to explain the date.     

Salt Tolerance of Seedling and Adult Bread Wheat Plants Based on Ion Contents and Agronomic Traits

Abstract

A greenhouse experiment was conducted on two salt‐tolerant, two moderately tolerant, and two sensitive Iranian and exotic bread wheat cultivars and their F₁ generations to investigate the effect of salt stress on ion contents of young leaves, biomass yield, and salt stress tolerance index. The materials were evaluated in gravel culture under high salinity (EC=22.5 dSm^?1) and nonstress (EC=2.0 dSm^?1) conditions. Results of stress intensity showed that K⁺/Na⁺ ratio, biomass yield, and Na⁺ concentration were most affected by salt stress. There was no genetic relationship between Mg²⁺ and Ca²⁺ contents with salt tolerance. However, strong relationships were observed among K⁺/Na⁺ ratio, biomass yield, and stress tolerance index. Factor analysis revealed four factors, which explained 99.79% of the total variation among characters. Three‐dimensional plots based on the first three factor scores confirmed that the most salt‐tolerant cultivar was Roshan (an old Iranian cultivar), and Roshan×Alvand and Kharchia×Roshan and their reciprocal crosses were the best salt‐tolerant crosses.     

Altered influx/efflux relations of nitrate in roots due to nutrient stress. II. Effect of calcium limitations

The effect of calcium (Ca²⁺), aluminum (Al³⁺), and high salinity stress on the influx‐efllux relations of nitrate (NO₃ ^‐) was investigated in barley and squash seedlings using continuous monitoring techniques and ¹³N labelling. After 24 h of Ca²⁺ deficiency NO₃ ^‐ influx was substantially reduced at the level of unsaturated NO₃ ^‐ uptake. With prolonged Ca²⁺ deficiency the repression of NO₃ ^‐influx drastically increased in squash involving irreversible impairment of the whole root function whereas the impairment only progressed more moderately in barley. Treatment with 160 μM Al³⁺ for 24 h also induced a repression of NO₃ ^‐ influx probably due to an interaction between Al³⁺ and Ca²⁺ ions. In both Ca²⁺ deficiency and Al³⁺ toxicity experiments, the NO₃ ^‐ efflux was only slightly affected. Suddenly imposed high salinity at a species‐specific level resulted in an instantaneous repression of NO₃ ^‐ influx accompanied by a heavy release of NO₃ ^‐ to the ambient nutrient solution. The results are discussed in the light of the key role which Ca²⁺ is suggested to play in membrane integrity and at the level of intracellular processes and in view of the relations to carrier‐mediated NO₃ ^‐ influx.     

Calcium (45CA2+) absorption by sorghum seedling root tips in the presence of ruthenium red and verapamil

Sorghum bicolor (L.) Moench. cv GP‐10, SC283, SC574, and Funk 6522DR seedling root tips (1 cm) absorption of calcium (⁴⁵Ca²⁺) in the presence of 0.1 mM ruthenium red (RR) and verapamil (0, 0.01, 0.1, 1.0, or 10 mM) was evaluated at pH 5.5. Verapamil was not inhibitory in Funk G522DR, significantly inhibited ⁴⁵Ca²⁺ absorption at 1.0 mM verapamil in GP‐10, SC283, and SC574 by 35, 65, and 55%, respectively. Genetic variation is documented. Additionally, as yet unrecognized physiological parameters seem to induce changes in response by the various cultivars.     

Vanadate influence on calcium (45Ca2+) absorption by sorghum root tips

One‐cm root‐tips of Sorghum bicolor (L.) Moench cv Funk G522DR, SC574, SC283, or GP‐10 were exposed to calcium (⁴⁵Ca²⁺) for 2‐hr at pH 5.5 in the presence of vanadate (0,0.1, 1.0, or 10.0 mM). Genetic variation in vanadate‐untreated absorption of ⁴⁵Ca²⁺ was observed. Vanadate inhibited ⁴⁵Ca²⁺ uptake in Funk G522DR, SC574, and GP‐10 linearly with the log concentration. In SC283, 0.1 mM vanadate significantly decreased ⁴⁵Ca²⁺ absorption; but, ⁴⁵Ca²⁺ absorption increased at higher vanadate concentrations.     

Tolerance of barley cultivars to an acid,aluminum‐toxic subsoil related to mineral element concentrations in their shoots

Abstract

Barley, Hordeum vulgare L., is extremely sensitive to excess soluble or exchangeable aluminum (Al) in acid soils having pH values below about 5.5. Aluminum tolerant cultivars are needed for use in rotations with potatoes which require a soil pH below 5.5 for control of scab disease. They are also potentially useful in the currently popular “low input, sustainable agriculture (LISA)”; in which liming even the plow layer of soil is not always possible or cost effective, or in situations where surface soils are limed but subsoils are acidic and Al toxic to roots. Ten barley cultivars were screened for Al tolerance by growing them for 25 days in greenhouse pots of acid, Al‐toxic Tatum subsoil (clayey, mixed, thermic, typic Hapludult) treated with either 750 or 4000 μg?g^‐1 CaCO₃ to produce final soil pH values of 4.4 and 5.7, respectively. Based on relative shoot dry weight (weight at pH 4.4/weight at pH 5.7 X 100), Tennessee Winter 52, Volla (England), Dayton and Herta (Denmark) were significantly more tolerant to the acid soil than Herta (Hungary), Kearney, Nebar, Dicktoo, Kenbar and Dundy cultivars. Relative shoot dry weights averaged 28.6% for tolerant and 14.1% for sensitive cultivar groups. Comparable relative root dry weights were 41.7% and 13.7% for tolerant and sensitive cultivars, respectively. At pH 4.4, Al concentrations were nearly three times as high in shoots of sensitive cultivars as in those of the tolerant group (646 vs. 175 μg?g^‐1), but these differences were reduced or absent at pH 5.7. At pH 4.4, acid soil sensitive cultivars also accumulated phosphorus concentrations that were twice as high as those in tolerant cultivars (1.2% vs. 0.64%). At pH 5.7, these P differences were equalized at about 0.7% for both tolerant and sensitive groups. At pH 4.4, shoots of the Al‐sensitive cultivar Nebar contained 1067 μg?g^‐1 Al and 1.5% P. Concentrations of Al and P in the shoots of acid soil sensitive cultivars grown at pH 4.4 exceeded levels reported to produce toxicity in barley. The observed accumulation of such concentrations of Al and P in the shoots of plants grown under Al stress is unusual and deserves further study.     

缺钙对不同钙效率番茄幼苗钙吸收及幼茎解剖结构的影响

采用两个钙效率有较大差异的番茄品种(04,05)研究了缺钙胁迫对幼苗钙素吸收动力学特性、钙在体内的吸收和分配及幼茎解剖结构的影响。结果表明,正常供钙下不同钙效率番茄品种存在吸钙速率的基因型差异,钙低效品种04钙高效品种05,经过缺钙胁迫后重新吸收钙的速率仍然以0405。正常供钙下,钙低效品种04生长量、钙吸收量均显著高于钙高效品种05,而缺钙处理下植株生长量、钙吸收量、钙含量显著低于05。缺钙下两品种的根冠比增加,05增加程度高于04。正常供钙下两品种表皮细胞、薄壁细胞和形成层细胞形状大小匀称,排列紧密,04茎木质部导管数较多;缺钙使两品种幼茎形成层细胞发育受到影响,尤以04影响显著,表明缺钙胁迫对04品种结构的影响远远高于05。     

Screening wheat and sorghum cultivars for aluminum sensitivity at low aluminum levels

Screening cultivars for aluminum (Al) tolerance is often conducted in acid soils or in complete nutrient solutions. The former method lacks precise measurements of Al, and the second requires high Al concentrations because of precipitation and chelation of the Al and is less representative of the actual environmental stresses to which plants must adapt. These experiments were designed to determine Al tolerance of wheat (Triticum aestivum L. em Thell) and sorghum (Sorghum bicolor L. Moench) using incomplete solutions with very low Al concentrations. Six wheat and five sorghum cultivars were screened for Al tolerance in solution culture with 0 to 10 μM Al and only Ca, K, Mg, NO₃, and Cl in the solutions. Plants were subjected to the solutions for 4 d, and the change in relative root length was measured. Solution Al levels and pH were measured after the termination of the experiments. ‘Atlas’ 66 and ‘Stacy’ were the most tolerant wheat cultivars ('Atlas 66’ = ‘Stacy’ ≥ ‘Monon’ ≥ ‘Scout 66’ ≥ ‘Arthur 71’ = ‘Oasis'). The wheat cultivars were effectively separated on a genetic response basis at 2 μM Al. Sorghum cultivars were uniform in their Al tolerance, but did show some separation at 1 μM Al (SC56 > Tx430 > ‘Funk GS22DR’ > SC283 = SC599). The pH and Al variations did not account for any of the differences observed, indicating that root length differences were caused by genetic control of response to high Al.     

Effects of NaCl and silicon on ion distribution in the roots,shoots and leaves of two alfalfa cultivars with different salt tolerance

Abstract

The effects of exogenous NaCl and silicon on ion distribution were investigated in two alfalfa (Medicago sativa. L.) cultivars: the high salt tolerant Zhongmu No. 1 and the low salt tolerant Defor. The cultivars were grown in a hydroponic system with a control (that had neither NaCl nor Si added), a Si treatment (1 mmol L^?1 Si), a NaCl treatment (120 mmol L^?1 NaCl), and a Si and NaCl treatment (120 mmol L^?1 NaCl + 1 mmol L^?1 Si). After 15 days of the NaCl and Si treatments, four plants of the cultivars were removed and divided into root, shoot and leaf parts for Na⁺, K⁺, Ca²⁺, Mg²⁺, Fe³⁺, Mn²⁺, Cu²⁺ and Zn²⁺ content measurements. Compared with the NaCl treatment, the added Si significantly decreased Na⁺ content in the roots, but notably increased K⁺ contents in the shoots and leaves of the high salt tolerant Zhongmu No.1 cultivar. Applying Si to both cultivars under NaCl stress did not significantly affect the Fe³⁺, Mg²⁺ and Zn²⁺ contents in the roots, shoots and leaves of Defor and the roots and shoots of Zhongmu No.1, but increased the Ca²⁺ content in the roots of Zhongmu No.1 and the Mn²⁺ contents in the shoots and leaves of both cultivars, while it decreased the Ca²⁺ and Cu²⁺ contents of the shoots and leaves of both cultivars under salt stress. Salt stress decreased the K⁺, Ca²⁺, Mg²⁺ and Cu²⁺ contents in plants, but significantly increased Zn²⁺ content in the roots, shoots and leaves and Mn²⁺ content in the shoots of both cultivars when Si was not applied. Thus, salt affects not only the macronutrient distribution but also the micronutrient distribution in alfalfa plants, while silicon could alter the distributions of Na⁺ and some trophic ions in the roots, shoots and leaves of plants to improve the salt tolerance.     

Differential zinc uptake and transport in sorghum varieties suited for different moisture regimes

Zinc absorption and transport were examined in M‐35 a drought resistant, and M‐47, a drought susceptible sorghum (Sorghum bicolor L. Moench) cultivar. Excised roots were employed to study the mechanisms of uptake at cellular level in these varieties.

The absorption over 0 to 130 μM ZnCl₂ followed a biphasic pattern with a second rise at 90 μM, a feature which was not observed in the absorption by roots of intact seedlings. While there were no differences in the patterns of absorption in the two cultivars, the transport to shoot in M‐35 followed a slower rate up to 90 μM than that in M‐47. When Zn uptake was examined for 6 hours, the absorption and transport showed a number of changes in phase, which were running parallel. The transport of Zn followed a higher rate in M‐47 than that in M‐35.

Phosphate decreased the uptake and also transport of Zn in both the varieties. However, Zn inhibited phosphate absorption and transport in intact seedlings differentially amongst the varieties. Further, the inhibition of Zn uptake was much less in M‐35 than in M‐47, a feature which will perhaps facilitate survival of M‐35 under water stress, a condition which would also limit phosphate availability.     

Agronomic effectiveness of phosphate rock and superphosphate for aluminum‐tolerant and non‐tolerant sorghum cultivars

Abstract

About 35% of soils in Venezuela are acid and low in available phosphorus (P). To solve this problem farmers lime and apply phosphate fertilizers to the soils, but both lime and fertilizers are expensive. A good alternative to overcome soil acidity is the use of aluminum (Al)‐tolerant cultivars. The objective of this study was to test the hypothesis, by use of a pot experiment, that sorghum cultivars tolerant to Al toxicity are able to use P from phosphate rock more efficiently than are susceptible cultivars. Three sorghum (Sorghum bicolor L. Moench) cultivars, Chaguaramas III (Ch), AI‐tolerant, Decalb D59 (D59), and Pioneer 8225 (Pi), both Al‐susceptible, were grown in the greenhouse for 20 and 35 days in two acid soils fertilized with 0 and 100 mg P kg^‐1 as triple superphosphate (SP) and Riecito phosphate rock (PR). Santa Maria soil was very low in available P (2 mg kg^‐1) and highly saturated in Al saturation (64.5%) and Pao soil was higher in available P (20 mg kg^‐1) and low in Al saturation (6.5%). Chaguaramas dry matter production, P uptake and root length was higher in Santa Maria soil as compared with Pi and D59 when grown with both SP and PR fertilization. Chaguaramas response to PR in Pao soil was not as good as in Santa Maria soil. The results of our experiment suggest that Al‐tolerant Ch is able to utilize P from PR more efficiently in soils like Santa Maria than Al‐susceptible cultivare Pi and D59.