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.     

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.     

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.     

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.     

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).     

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.     

Diltiazem influence on mineral nutrient uptake by sorghum primary root tips

Seedling sorghum [Sorghum bicolor (L.) Moench. cv GP10, SC283, SC574, and Funk G522DR] primary root tip (1‐cm) content of calcium (Ca), zinc (Zn), iron (Fe), magnesium (Mg), copper (Cu), boron (B), manganese (Mn), and phosphorus (P) in response to a known Ca‐channel blocker (diltiazem, 0,0.1, 1, or 10 mM) was measured after a 1‐hr exposure to Hoagland and Arnon complete mineral nutrient solution. Diltiazem (10 mM) significantly decreased content of Ca, Mn, and Mg in all four cultivars, P, Zn, and Fe in three cultivars, Cu in two cultivars, and B content was not altered. Differences among cultivars was observed in ion contents by the diltiazem untreated controls for all elements. Multiple avenues of ion movement across the plasma membrane are evident. Genetically determined mechanisms and rates of activity between cultivars were demonstrated.     

Differences in sorghum cultivar root response to concomitant excess hydrogen (H+) and manganese (Mn2+) ion applications

Sorghum [Sorghum bicolor (L.) Moench] seeds were planted into ‘white quartz flintshot’ sand and watered with 0.01M sodium acetate at pH 6.0, 5.5, 5.0, 4.5, or 4.0 plus 0, 1.4, 14.0, or 140.0 mg/L manganese (Mn²⁺). Cultivars used were 38M, 58M, GP‐140, SC283, SC574, 5C599, TAM428, and Funk G522DR. Lengths, fresh weights, and dry weights of roots were decreased as hydrogen (H⁺) or Mn²⁺ concentrations increased. Interactions of H⁺ and Mn²⁺ concentrations were synergistic for length, fresh weight, and dry weight of roots in 38M and 58M. Interaction of H⁺ and Mn²⁺ stresses on root length was additive in GP‐140, SC283, SC574, SC599, and TAM428 but interactions of these stresses were antagonistic in root length of Funk GS22DR.     

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.     

Influence of H+ Ca++, and Mn++ on the development of amylase in the endosperm of several sorghum cultivars 1

Sorghum [Sorghum bicolor (L.) Moench] seeds (Funks G522DR) were planted in ‘white quartz flintshot’ and watered with 0.01 M NaAc buffer at pH 4.0, 4.5, 5.0, 5.5, or 6.0 ± Ca⁺⁺ (0, 10, 100 ppmw) or Mn⁺⁺ (0, 1.4, 140.0 ppmw) and grown for seven days in a growth chamber. Endosperm amylase contents, quantitatively and qualitatively, were dependent upon the environmental conditions during germination. H⁺ concentration at pH 4.0 strongly induced a decrease in amylase activity which was relieved as the pH was raised to pH 6.0. Ca⁺⁺ greatly increased endosperm amylase contents. Mn⁺⁺ (1.4 ppmw) tended to increase endosperm amylase contents while Mn⁺⁺ (140.0 ppmw) strongly decreased endosperm amylase content. In the cultivar SC283, endosperm amylase contents were nearly double those found in Funks G522DR while SC574 had, at most, one half the endosperm amylase content of Funks G522DR endosperm. Endosperm amylase contents of SC283 were pH tolerant while those of Funks G522DR and SC574 were highly pH sensitive. These data further demonstrate the plasticity of plants growing under adverse environmental conditions.     

Nifedipine influence on calcium and aluminum absorption in roots of three sorghum cultivars

A 1,4‐dihydroxypyridine type of ion channel blocker, nifedipine [1,4‐dihydro‐2,6‐dimethyl‐4‐(2‐nitrophenyl)‐3,5‐pyridinedicarboxylate dimethyl ester], was tested on the root absorption of Al³⁺ and Ca²⁺ by sorghum [Sorghum bicolor (L.) Moench] cultivars with varying acid stress tolerance. In an acid stress sensitive cultivar, Funk G522DR, nifedipine (1 μM) influenced Ca²⁺ but not Al³⁺ absorption. In one acid stress tolerant cultivar, SC574, nifedipine (1 μM) influenced both Ca²⁺ and Al³⁺ absorption. In a second acid stress tolerant cultivar, SC283, nifedipine (1 μM) did not influence Ca²⁺ but did influence Al³⁺ absorption. Considerable genetic diversity is present in Ca²⁺ and Al³⁺ absorption between sorghum cultivars.     

Sorghum seedling root growth as influenced by H+, CA++, and MN++ concentrations 1

Root response mechanisms for acid soil tolerance adaptability are generally unknown. Sorghum [Sorghum bicolor (L.) Moench] cultivars (Funk G522DR, GP140, SC599, TAM428, SC283, and SC574) were grown in white quartz flintshot sand and watered with 0.01M sodium acetate buffer at pH 4.0, 4.5, 5.0, 5.5, or 6.0 and Ca⁺⁺ (0, 10, 100 mgl^‐1 as CaCl₂) or Mn⁺⁺ (0, 1.4, or 140.0 mgl^‐1 as HnCl₂). At the acid soil tolerance impact response phase (< 10 days old), Ca⁺⁺ did not influence initial root growth. Increased H⁺ concentration inhibited juvenile root growth equivalently in all six cultivars. This inhibition was reversed by exogenous GA₃ in Funks G522DR but not in SC283 or SC574. Excess Mn⁺⁺ (140 mgl^‐1) further decreased root growth. Induction of an auxinase inhibitor by GA₃ would support a hypothesis of H⁺ concentration influence on IAA transport and/or availability. Root growth matched IAA water partitioning and exogenous IAA (10^‐10 and 10^‐9 M) reversed the H⁺ concentration influence on root growth of SC283. We suggest that low pH (<4.8) soil influence on root growth is explicable as an influence on IAA synthesis and/or transport and that excess Mn⁺⁺, which is known to induce IAA oxidation, further exacerbates the deleterious growing conditions.     

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.     

Plant mineral contents of root tips from four sorghum cultivars after exposure to the anion channel blocker,sits

SITS (0, 0.01, 0.1, or 1.0 mM) influence on the absorption (1 hr) by 1‐cm root tips of Sorghum bicolor (L.) Moench cv GP‐10, SC 283, SC 574, or Funk G522DR seedlings of calcium (Ca), boron (B), phosphorus (P), zinc (Zn), manganese (Mn), iron (Fe), magnesium (Mg), and copper (Cu) from an Hoagland and Arnon complete mineral nutrient solution was evaluated by inductively coupled plasma emission spectrophotometry (ICP). Cultivar variation in response to SITS within each element was found. Multiple mechanisms of control for the absorption of each element among cultivars were evident.     

H+, Ca++, and Mn++ influence on sorghum seedling shoot growth

Plant response mechanisms for acid soil tolerance adaptability are generally unknown. Sorghum [Sorghum bicolor (L.) Moench] cultivars (Funk G522DR, GP 140, SC 599, TAM 428, SC 283, and SC 574) were grown in white quartz flintshot sand and watered with 0.01 M sodium acetate buffer at pH 4.0, 4.5, 5.0, 5.5, or 6.0 with concurrent treatments of Ca⁺⁺ (0, 10, 100 mgl^‐1 as CaCl₂) or Mn⁺⁺ (0, 1.4, 140.0 mgl^‐1 as MnCl₂). At the acid soil tolerance impact response phase (<10 days old), Ca⁺⁺ or Mn⁺⁺ did not influence seed germination (i.e., radicle exsertion). Ca⁺⁺ did not influence initial shoot growth. Increased H⁺ concentration greatly inhibited juvenile shoot growth equivalently in all six cultivars. This inhibition was explicable as an influence of gibberellic acid (GA) availability to the aleurone layer and was explained as an accumulation (partitioning) of GA into lipid cellular constituents. Excess Mn⁺⁺ further exacerbates this condition by limiting GA biosynthesis.     

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).     

Influence of nitrate‐nitrogen and ammonium‐nitrogen on calcium (45Ca2+) absorption in sorghum root tips

Abstract

Root‐tip, 1‐cm of Sorghum bicolor (L.) Moench cv SC283, SC574, GP‐10, and Funk G522DR were exposed to calcium (⁴⁵Ca²⁺) at pH 5.5 for 2‐hr in the presence of nitrate‐nitrogen (NO3^?‐N) or ammonium‐nitrogen (NH4+‐N). Nitrate (0.1 mM) induced significantly increased ⁴⁵Ca uptake in Funk G522DR, SC283, and GP‐10 while 0.01 mM NO₃ ^?‐N induced significantly increased ⁴⁵Ca'uptake in SC574, but ⁴⁵Ca absorption was significantly decreased at 1 mM NO₃—N. In the presence of the NH4⁺ ion, ⁴⁵Ca uptake was increased up to 8X that of the NH₄ ⁺‐N untreated roots. When ammonium chloride (NH₄CI) was used, the Cl^? tended to induce an increased ⁴⁵Ca uptake. Cultivar variation was present.     

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.     

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

Influence of magnesium sulfate (MgSO₄ ‐ 0, 0.01, 0.1, or 1.0 mM) on absorption of calcium as ⁴⁵Ca²⁺ in 2‐hr exposures at pH 5.5 by 1‐cm root‐tips of Sorghum bicolor (L.) Moench. cv SC574, SC283, GP‐10, and Funk G522DR was undertaken. Magnesium (0.01 mM) induced a significantly increased and 1.0 mM induced a significantly decreased ⁴⁵Ca²⁺ uptake.     

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.