Root Potassium Concentration Research Articles

Coordination of Root Traits and Rhizosphere Microbial Community in Tea (Camellia sinensis L.) Plants under Drought and Rehydration

Soil drought and rehydration have an immense impact on plant physiology and productivity, whereas the response of plant–microbe interactions to varied water availability remains largely elusive. In this study, two tea (Camellia sinensis L.) cultivars, Longjing43 and Yingshuang, were subjected to drought followed by rehydration. Soil drought significantly induced the elongation of taproots in the Yingshuang cultivar after two weeks of drought. Moreover, the four-week drought significantly reduced the root dry mass and root nitrogen, phosphorus, and potassium concentrations in both tea cultivars. Two-week rehydration recovered the root potassium concentration in the two tea cultivars, revealing the rapid response of root potassium levels to water conditions. Drought and rehydration also resulted in shifts in rhizosphere microbial diversity. A four-week drought reduced microbial alpha diversity in Longjing43 but not in the Yingshuang cultivar, and rehydration was effective in restoring alpha diversity in Longjing43. The rhizosphere microbial community tended to recover to the initial stages after rehydration in Longjing43 but not in the other cultivar. In addition, 18 microbial genera were identified as the featured microbial taxa in response to varied water availability, and a rare genus Ignavibacterium was significantly increased in the Longjing43 cultivar by rehydration after a four-week drought. Furthermore, root nitrogen, phosphorus, potassium levels, and dry mass were positively correlated with the microbial alpha diversity, while the taproot length was negatively correlated, suggesting the crucial role of plant–microbe interactions in response to drought and rehydration. Moreover, the root phosphorus concentration and taproot length also had significant effects on microbial beta diversity, further confirming their effects on the community structure of the rhizosphere microbiome. Overall, this study provides insights into the effects of drought on plant–microbe interactions in the rhizosphere of tea plants. These findings are important for harnessing the roles of the tea rhizosphere microbiome under drought.

Impact of reduced atmospheric CO2 and varied potassium supply on carbohydrate and potassium distribution in grapevine and grape berries (Vitis vinifera L.)

To assess the robustness of the apparent sugar-potassium relationship during ripening of grape berries, a controlled-environment study was conducted on Shiraz vines involving ambient and reduced (by 34%) atmospheric CO2 concentrations, and standard and increased (by 67%) soil potassium applications from prior to the onset of ripening. The leaf net photoassimilation rate was decreased by 35% in the reduced CO2 treatment. The reduction in CO2 delayed the onset of ripening, but at harvest the sugar content of the berry pericarp was similar to that of plants grown in ambient conditions. The potassium content of the berry pericarp in the reduced CO2 treatment was however higher than for the ambient CO2. Berry potassium, sugar and water content were strongly correlated, regardless of treatments, alluding to a ternary link during ripening. Root starch content was lower under reduced CO2 conditions, and therefore likely acted as a source of carbohydrates during berry ripening. Root carbohydrate reserve replenishment could also have been moderated under reduced CO2 at the expense of berry ripening. Given that root potassium concentration was less in the vines grown in the low CO2 atmosphere, these results point toward whole-plant fine-tuning of carbohydrate and potassium partitioning aimed at optimising fruit ripening.

Tamarack response to salinity: effects of sodium chloride on growth and ion, pigment, and soluble carbohydrate levels

The extraction of bitumen from oil sands can increase levels of sodium and chloride in boreal forest soils. A study was designed to test the effect of 30 and 60 mmol/L NaCl on 6-month-old tamarack (Larix laricina (Du Roi) K. Koch.) seedlings grown in aerated nutrient solutions. After 40 days of treatment in a growth chamber, 30 mmol/L NaCl caused injury to old needles and decreased shoot biomass, root potassium concentration, root soluble carbohydrate content, as well as chlorophyll a, chlorophyll b, and carotenoid levels in old needles. Sodium content of seedlings exposed to 30 mmol/L NaCl was higher in roots than in stems and new needles, while chloride content was higher in both old and new needles. Sodium and chloride concentrations were similar in new needles and in old needles. Seedlings exposed to 60 mmol/L NaCl showed injury in both old and new needles and lower root and shoot biomass, root magnesium and potassium concentrations, and both root and stem soluble carbohydrate levels. Furthermore chlorophyll a, chlorophyll b, and carotenoid levels were lower in all needles than in the control. Sodium and chloride contents of seedlings treated with 60 mmol/L NaCl were higher in old and new needles than in roots and stems. The results suggest that tamarack seedlings have a moderate tolerance to salinity, and when exposed to 30 mmol/L NaCl the seedlings could avoid injury by maintaining a relatively high K+/Na+ ratio in new needles and controlling Na+ transport to the shoots.

Effect of soil potassium on yield and quality of diverse sugar beet genotypes

Aiming at determination differences in leaf and root potassium concentration of diverse sugar beet genotypes as well as its effect on sugar beet root quality and yield. Investigations comprising 15 sugar beet genotypes (five multigerm lines, five hybrids and five monogerm lines) were carried out on two soil types (Calcic luvisol: L-1 and L-3 and Calcic gleysol: L-2 and L-4) during two growing seasons. Root yield of the investigated genotypes on Calcic luvisol (50 t/ha) was higher, than on Calcic gleysol (34 t/ha). In general, multigerm lines were known for the highest leaf potassium concentration (2.75%), lowest root one (3.78 mmol/100 g root), highest sugar content (13.8%) and best root extractable sugar (1.5%). Monogerm lines had the lowest leaf potassium concentration (2.51%), highest root one (4.24 mmol/100 g root), lowest sugar content (12.9%), and the poorest extractable sugar (10.7%). Root yield of the investigated hybrids (48 t/ha) was higher by 16% compared to multigerm lines yield (42 t/ha) and as much as 35% higher compared to monogerm lines (36 t/ha). Sugar beet root potassium was in significantly negative correlation with sugar content at three localities (L-1: r = –0.485**, L-2: r = –0.096, L-3: r = –0.687**, L-4: r = –0.337**) whereas at all four localities it was in negative correlation with extractable sugar (L-1: r = –0.634**, L-2: r = –0.407**, L-3: r = –0.930**, L-4: r = –0.749**). Potassium concentration in sugar beet leaf was in significant positive correlation with sugar content at three localities (L-1: r = 0.382**, L-2: r = 0.231, L-3: r = 0.717**, L-4: r = 0.516**).

Lead distribution in corn seedlings ( Zea mays L.) and its effect on growth and the concentrations of potassium and calcium

It was observed that dry weight yield is not a sensitive parameter withwhich to assess lead toxicity to plants. Elongation growth of corn seedlingroots was more sensitive to lead than shoot growth and was inhibited by allconcentrations tested (10−5, 10−4, and 10−3 M).It was positively correlated with potassium concentration and negativelycorrelated with lead concentration in the roots. Negative correlation also wasobserved between lead concentration and potassium concentration in roots. It ispostulated that inhibition of corn root growth is connected with potassiumleakage from root cells. The toxic action of lead on corn seedling mesocotylandcoleoptile growth was not correlated with potassium concentration in planttissue and correlation between growth and lead concentration was low. Inseedlings treated with 10−4 and 10−3 M lead the growthof mesocotyl and coleoptile was affected similarly, although the concentrationof lead was threefold higher in mesocotyl tissue than in coleoptile tissue. It isproposed that depression of corn seedlings shoot growth is not an effect ofpotassium leakage or lead accumulation but of an unknown signal induced inroots, as a response to exposure to lead, which is transmitted to shoots. Thepositive correlation between lead and calcium concentrations found in seedlingroots might be connected with high constitutional tolerance of corn to lead.Since the first 8 mm of an apical root accounts for 50% of thelead accumulated by the whole root, it is postulated that rhizofiltration oflead contaminated waters should be more efficient when plant species withhighly branched root systems are used.

Calcium and potassium-enhanced growth and yield of tomato under sodium chloride stress

The effects of salinization of nutrient solutions with NaCl, Ca(NO 3) 2 and KNO 3 on selected root, leaf and yield parameters of five tomato cultivars were investigated under greenhouse condition. Results of the study showed that addition of 50 mM NaCl to nutrient solution significantly reduced root volume and fresh weight, calcium and potassium concentrations, leaf number and fresh weight, as well as fruit yield. Addition of calcium and potassium, either alone or in combination with each other, to saline nutrient solution increased root volume, fresh weight and calcium concentration, leaf fresh weight and fruit yield per plant. Moreover, root potassium concentration and leaf fresh weight increased when 20 mM Ca(NO 3) 2 was added to saline nutrient solution but not with 2 mM KNO 3. Leaf number, on the other hand, increased with K but not with Ca application to the saline nutrient solution. Of the five cultivars screened, ‘Pearson’ showed the best performance followed by ‘Montecarlo’, ‘UC 82L’, ‘Pakmore’ and ‘Strain B’ in decreasing order.

A comparison of the effects of central ν peripheral bolus injections of potassium chloride on aortic root potassium concentrations in swine

Clinically relevant doses of potassium chloride (equivalent to 2 mEq/60 kg of body weight) were administered as rapid intravenous (IV) boluses to healthy halothane-anesthetized pigs. Potassium was given either peripherally through a standard IV ear catheter or centrally through the central venous port of a pulmonary artery catheter. Multiple injections were made in each pig, and cardiac output was varied by changing end-tidal halothane concentration. The aortic root potassium concentration was measured every three to six seconds for 90 seconds following potassium administration in each pig. Monitored variables included end-tidal halothane, end-tidal carbon dioxide, pulmonary artery pressure, mean arterial blood pressure, cardiac output, electrocardiogram, and temperature. Following both peripheral and central administration of potassium chloride, aortic root potassium increased significantly. However, the time required to achieve the peak aortic root potassium concentration was significantly less after central administration. In addition, the change in aortic root potassium concentration was greater following central administration compared with peripheral. The change in aortic root potassium concentration correlated inversely with cardiac output only after central, but not peripheral injection. Despite marked transient hyperkalemia in all animals, no electrocardiographic evidence of hyperkalemia could be demonstrated. It is concluded that small bolus doses of potassium chloride (2 mEq/60 kg) can be given safely either peripherally or centrally in normal, hemodynamically stable swine.

Potassium Influx into Maize Root Systems

Potassium influx into roots of dark-grown decapitated maize seedling (Zea mays L., cv Pioneer 3369A) was examined in presence and absence of ambient ammonium and at various root potassium concentrations. Six-day old seedlings which were dependent on the endosperm reserves for their energy source were exposed to KCl (labeled with (86)Rb) ranging from 5 to 200 micromolar. At both low (13 micromoles per gram fresh weight) and high (100 micromoles per gram fresh weight) root potassium concentration, isotherms indicated two potassium influx systems, one approaching saturation at 50 to 100 micromolar potassium and an additional one tentatively considered to be linear. A mixed-type inhibition by ammonium for the low-concentration saturable system was indicated by a concomitant decrease in V(max) and increase in K(m). High root potassium concentration decreased V(max) but had little effect on K(m) of this system. The rate constant for the second quasilinear system was decreased by ambient ammonium and by high root potassium status. Transfer of high potassium roots to potassium-free solutions resulted in an increase in influx within 2 hours; by 24 hours influx significantly exceeded that of roots not previously exposed to potassium. In roots of both low and high root potassium concentrations, potassium influx was restricted progressively as ambient ammonium increased to about 100 micromolar, but there was little further inhibition as ammonium concentrations increased beyond that to 500 micromolar. The data imply that potassium influx has two components, one subject to inhibition by ambient ammonium and one relatively resistant.

Acclimation of potassium influx in rye (Secale cereale) to low root temperatures

The influx of K(+)((86)Rb(+)) into intact roots of rye (Secale cereale L. cv. Rheidal) exposed to a differential temperature (DT) between the root (8° C) and shoot (20° C) is initially reduced compared with warm-grown (WG) controls with both shoot and root maintained at 20° C. Over a period of 3 d, however, K(+)-influx rates into DT plants are restored to levels similar to or greater than those of the WG controls, the absolute rates of K(+) influx being strongly dependent upon the shoot/root ratio. Acclimation in DT plants results in a reduction of K(+) influx into the apical (0-2 cm) region of the seminal root which is associated with a compensatory increase in K(+) influx into the more mature, basal regions of the root. Values of V max and apparent K m for K(+) influx into DT plants were similar to those for WG plants at assay temperatures of 8° C and 20° C except for an increase in the apparent K m at 8° C. The influx of K(+) from solutions containing 0.6 mol·m(-3) K(+) into both WG and DT plants was found to be linearly related to assay temperature over the range 2-27° C, and the temperature sensitivity of K(+) influx to be dependent upon shoot/root ratio. At high shoot/root ratios, the ratio of K(+) influx at 20° C:K(+) influx at 8° C for WG plants approached a minimum value of 1.9 whereas that for DT plants approached unity indicating that K(+) influx into DT plants has a large temperature-insensitive component. Additionally, when plants were grown in solutions of low potassium concentration, K(+) influx into DT plants was consistently greater than that into WG plants, in spite of having a greater root potassium concentration ([K(+)]int). This result indicates some change in the regulation of K(+) influx by [K(+)]int in plants exposed to low root temperatures. We suggest that K(+) influx into rye seedlings exposed to low root temperatures is regulated by the increased demand placed on the root system by a proportionally larger shoot and that the acclimation of K(+) influx to low temperatures may be the result of an increased hydraulic conductivity of the root system.

Identification and selection for salt tolerance in lucerne (Medicago sativa L.)

Variation existed between plants of the lucerne (Medicago sativa L.) cultivar CUF 101 for dry matter production, shoot number and length, and leaf damage when grown for 70 days under 250 mM NaCl (15 h photoperiod, 20�C day, 10�C night). Salt tolerance evaluation using the criteria percentage leaf damage (percentage of total number of leaves with complete or partial necrosis) and length of the main shoot, isolated plants which showed salt tolerance of reasonably high heritability (h2=0.41). Two generations of recurrent selection for tolerance significantly increased the mean population tolerance without decreasing production under non-saline conditions. While both sodium and chloride concentrations of the shoot were lower in the tolerant than in less tolerant plants, chloride was more closely associated with salt tolerance than sodium. Sodium and chloride concentrations in the roots did not vary with the level of salt tolerance. No association of shoot and root potassium concentration with tolerance was evident. Selection for salt tolerance in lucerne plants using percentage leaf damage of less than 10% as the main criterion should give a rapid response to selection. The efficiency of selection may be increased if selection is based on the efficiency of chloride exclusion from the shoots and/or the level of chloride tolerated by the shoots prior to leaf damage becoming evident.