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.     

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).     

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 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.     

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.     

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.     

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.     

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.     

Acid‐soil‐stress influence on mineral‐ion contents of sorghum leaves and juvenile panicles

Sorghum [Sorghum bicolor (L.) Moench cv RTX430, SC214, SC574, SC599, TAM428, and SC326xSC103] were grown on soils of pH 4.2 or 6.2–6.5. Leaf and nonexserted juvenile panicle tissues were collected at 75 days after planting. Fresh and dry weights were measured and element contents [sulfur (S), phosphorus (P), magnesium (Mg), calcium (Ca), potassium (K), zinc (Zn), iron (Fe), and copper (Cu)] were measured by atomic absorption. Significant cultivar differences in ion concentration (μmol/g dry weight) were found. Juvenile panicles had higher ion concentration (μmol/g dry weight) [S, P, Mg, Ca, K, Zn, and Cu) than leaves. Within leaf tissue, ion concentration (μmol/g dry weight) was correlated with tissue water content (g water/g dry weight).     

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.     

Iron and zinc absorption characteristics and copper inhibitions in cucurbitaceae

Iron and Zn absorption, interactions, and Cu inhibitions were characterized in cucumber (Cucumis sativus L.), watermelon (Citrullus lanatus Thunb.), and pumpkin (Cucurbita moschata Poir.) by kinetic parameters V_max and K_m. Influx and V_max values for Fe and Zn absorption decreased in each species as plant age increased. For the Michaelis constant, K_m, Fe values in cucumber and watermelon and Zn values in watermelon and pumpkin were relatively unchanged with increased plant age. K_m values for Zn absorption in cucumber and Fe absorption in pumpkin decreased as plant age increased. Among species, watermelon appeared to have a particularly effective uptake mechanism for Zn at low solution concentrations. Non‐competitive inhibition of Zn absorption by Fe (20, 50 uM) was indicated in each species. Iron uptake in pumpkin was inhibited non‐competitively by Zn (5, 10 uM), however no significant effects of Zn on Fe absorption were evident in either watermelon or cucumber. Copper (0.5, 1, 5 uM) inhibited uptake of Fe non‐competitively and Zn competitively in each species.     

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.     

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.     

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.     

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.     

Significance of Wheat Flour Particle Size on Sponge Cake Baking Quality

We evaluated the effect and magnitude of flour particle size on sponge cake (SC) baking quality. Two different sets of wheat flours, including flours of reduced particle size obtained by regrinding and flour fractions of different particle size separated by sieving, were tested for batter properties and SC baking quality. The proportion of small particles (<55 μm) of flour was increased by 11.6–26.9% by regrinding. Despite the increased sodium carbonate solvent retention capacity, which was probably a result of the increased starch damage and particle size reduction, reground flour exhibited little change in density and viscosity of flour‐water batter and produced SC of improved volume by 0.8–15.0%. The volume of SC baked from flour fractions of small (<55 μm), intermediate (55–88 μm), and large (>88 μm) particles of soft and club wheat was in the range of 1,353–1,450, 1,040–1,195, and 955–1,130 mL, respectively. Even with comparable or higher protein content, flour fractions of intermediate particle size produced larger volume of SC than flour fractions of large particle size. The flour fractions of small particle size in soft white and club wheat exhibited lower flour‐water batter density (102.6–105.9 g/100 mL) than did those of large and intermediate particle fractions (105.2–108.2 g/100 mL). The viscosity of flour‐water batter was lowest in flour fractions of small particle size, higher in intermediate particles, and highest in large particles. Flour particle size exerted a considerable influence on batter density and viscosity and subsequently on SC volume and crumb structure. Fine particle size of flour overpowered the negative effects of elevated starch damage, water absorption, and protein content in SC baking.     

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.     

Seed triglyceride content and glyoxysomal activity variation in sorghum cultivars 1

Three sorghum [Sorghum bicolor (L) Moench] cultivars (Funk G522DR, SC283, and SC574) were germinated for 4‐days in sand and the isocitric lyase activity of the embryos was assayed. Glyoxysomal activities (nmol/g fresh weight/min) were: Funk G522DR (593.6), SC574 (117.6), and SC283 (6.5). Seed triglyceride contents were 26.96, 14.88, and 10.80 (μ triglyceride fatty acid/g fresh weight) for Funk G522DR, SC574, and SC283, respectively, with approximately 90% of the triglyceride being in the embryos which constituted 15–21% of the total seed weight. SC574 and SC283 are acid soil tolerant cultivars. Association of high glyoxysomal activity and very low amylase activity in SC574 and the reverse relative activities in SC283 explains the differences in growth of these two cultivars during the seedling impact phase under acid soil conditions. High glyoxysomal and amylase activities in acid soil sensitive Funk G522DR indicates that the acid soil response in juvenile sorghum seedlings is a multi‐factorial influence.     

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).