硅钾肥配施对水稻茎秆理化性状及抗倒伏能力的影响

该研究以易倒伏品种‘B优827’为试验材料,通过分析硅钾肥配合施用对水稻茎秆的弯曲力矩、抗折力以及倒伏指数的影响,探索通过肥料调控提高水稻抗倒伏能力的方法与技术措施。结果显示:(1)硅钾肥配施能显著增加水稻基部节间茎秆直径和壁厚,缩短节间长度,并在低硅中钾处理(T2,硅肥300kg/hm2、钾肥400kg/hm2)下基部各节间长度缩短幅度最大(12.44%~20.80%),直径和壁厚增加幅度分别为2.82%~5.76%、22.95%~28.57%。(2)硅钾肥配施处理后,水稻基部各节间纤维素、木质素及灰分含量显著变化,并以低硅中钾处理(T2)差异较显著,且基部节间木质素含量分别比对照显著提高14.55%、8.67%、7.73%。(3)硅钾肥配施处理能显著增加水稻基部节间抗折力,降低倒伏指数,同时仍以低硅中钾处理(T2)的抗折力最大、倒伏指数最小,对提高‘B优827’植株抗倒伏能力效果最好。研究表明,合理的硅钾肥配比(硅肥300kg/hm2、钾肥400kg/hm2)能显著增加易倒伏水稻品种‘B优827’的茎秆壁厚和直径,缩短基部节间长度,提高抗折力,同时还能增加其基部节间木质化程度,最终增强植株抗倒伏能力;硅钾肥配合施用可通过改善茎秆物理化学特性有效增强易倒伏水稻植株的抗倒伏能力。     

The effect of electrical gradients on current fluctuations and impedance recorded fromNecturus gallbladder

Summary Transepithelial current fluctuations were recorded inNecturus gallbladder, clamped at negative as well as positive potentials up to 64 mV. With NaCl-Ringer's (+10mm TAP) on both sides a mucosa-negative potential enhanced the relaxation noise component, present at zero potential, and produced peaking in the power spectrum at potentials above –36mV. Concomitantly at these potentials an inductive as well as a capacitive low-frequency feature appeared in the impedance locus. Clamping at positive potentials of 18 mV suppressed the relaxation noise component. At potentials above 51mV the spectral values increased predominantly at low frequencies. In this case the power spectrum showed only a 1/f noise component. The experiments confirm the previous finding that a K⁺ efflux through fluctuating apical K⁺ channels exists under normal conditions. With serosal KCl-Ringer's the initial Lorentzian component was enhanced at negative but suppressed at positive potentials. The increase at negative potentials was less pronounced than in experiments with NaCl-Ringer's on both sides, indicating saturation of the fluctuating K⁺ current component. With mucosal KCl-Ringer's a negative potential depressed the initial relaxation noise component, whereas it was enhanced at +18 mV clamp potential. In the latter case an additional Lorentzian component became apparent at higher frequencies. At potentials of 36 mV and above the low-frequency Lorentzian disappeared whereas the corner frequency of the high-frequency component increased. The latter experiments demonstrate that the relaxation noise component inNecturus gallbladder consists of two superimposed Lorentzians. As the relaxation times of these two components behave differently under an electrical field, there may exist two different types of K⁺ channels. It is demonstrated that peaking in the plateau of power spectra can be explained by frequency-dependent attenuation effects, caused by a polarization impedance.     

Auto‐phosphorylation of a voltage‐gated K+ channel controls non‐associative learning

Here, we characterize a new K⁺ channel–kinase complex that operates in the metazoan Caenorhabditis elegans to control learning behaviour. This channel is composed of a pore‐forming subunit, dubbed KHT‐1 (73% homology to human Kv3.1), and the accessory subunit MPS‐1, which shows kinase activity. Genetic, biochemical and electrophysiological evidence show that KHT‐1 and MPS‐1 form a complex in vitro and in native mechanosensory PLM neurons, and that KHT‐1 is a substrate for the kinase activity of MPS‐1. Behavioural analysis further shows that the kinase activity of MPS‐1 is specifically required for habituation to repetitive mechanical stimulation. Thus, worms bearing an inactive MPS‐1 variant (D178N) respond normally to touch on the body but do not habituate to repetitive mechanical stimulation such as tapping on the side of the Petri dish. Hence, the phosphorylation status of KHT‐1–MPS‐1 seems to be linked to distinct behavioural responses. In the non‐phosphorylated state the channel is necessary for the normal function of the touch neurons. In the auto‐phosphorylated state the channel acts to induce neuronal adaptation to mechanical stimulation. Taken together, these data establish a new mechanism of dynamic regulation of electrical signalling in the nervous system.     

Structural Insight into Layer Gliding and Lattice Distortion in Layered Manganese Oxide Electrodes for Potassium‐Ion Batteries

Potassium‐ion batteries (PIBs) are an emerging, affordable, and environmentally friendly alternative to lithium‐ion batteries, with their further development driven by the need for suitably performing electrode materials capable of reversibly accommodating the relatively large K⁺. Layer‐structured manganese oxides are attractive as electrodes for PIBs, but suffer from structural instability and sluggish kinetics of K⁺ insertion/extraction, leading to poor rate capability. Herein, cobalt is successfully introduced at the manganese site in the K_xMnO₂ layered oxide electrode material and it is shown that with only 5% Co, the reversible capacity increases by 30% at 22 mA g^‐1 and by 92% at 440 mA g^‐1. In operando synchrotron X‐ray diffraction reveals that Co suppresses Jahn–Teller distortion, leading to more isotropic migration pathways for K⁺ in the interlayer, thus enhancing the ionic diffusion and consequently, rate capability. The detailed analysis reveals that additional phase transitions and larger volume change occur in the Co‐doped material as a result of layer gliding, with these associated with faster capacity decay, despite the overall capacity remaining higher than the pristine material, even after 500 cycles. These results assert the importance of understanding the detailed structural evolution that underpins performance that will inform the strategic design of electrode materials for high‐performance PIBs.     

Reduction in number of sarcolemmal KATP channels slows cardiac action potential duration shortening under hypoxia

The cardiovascular system operates under demands ranging from conditions of rest to extreme stress. One mechanism of cardiac stress tolerance is action potential duration shortening driven by ATP-sensitive potassium (K_ATP) channels. K_ATP channel expression has a significant physiologic impact on action potential duration shortening and myocardial energy consumption in response to physiologic heart rate acceleration. However, the effect of reduced channel expression on action potential duration shortening in response to severe metabolic stress is yet to be established. Here, transgenic mice with myocardium-specific expression of a dominant negative K_ATP channel subunit were compared with littermate controls. Evaluation of K_ATP channel whole cell current and channel number/patch was assessed by patch clamp in isolated ventricular cardiomyocytes. Monophasic action potentials were monitored in retrogradely perfused, isolated hearts during the transition to hypoxic perfusate. An 80–85% reduction in cardiac K_ATP channel current density results in a similar magnitude, but significantly slower rate, of shortening of the ventricular action potential duration in response to severe hypoxia, despite no significant difference in coronary flow. Therefore, the number of functional cardiac sarcolemmal K_ATP channels is a critical determinant of the rate of adaptation of myocardial membrane excitability, with implications for optimization of cardiac energy consumption and consequent cardioprotection under conditions of severe metabolic stress.     

Effects of gramicidin and tryptophan-N-formylated gramicidin on the sodium and potassium content of human erythrocytes

Summary

In order to get a better understanding in the mechanism by which tryptophan-N-formylated gramicidin (NFG) and gramicidin kill the malaria parasite Plasmodium falciparum in vitro, we studied the capacity of these peptides to change the potassium, as well as the sodium, composition of normal human erythrocytes, and their ability to cause cell lysis. It is shown that both peptides are able to induce potassium leakage from, and sodium flux into, erythrocytes in such a manner that it is most likely that they are able to form cation channels in the membrane of these cells. For both peptides, potassium efflux proceeds at a faster rate than sodium influx, but this difference is greater for NFG than for gramicidin. This explains the observation that gramicidin is more lytic than NFG is, even when comparing concentrations that show the same antimalarial activity. The finding that gramicidin is approximately 10 times more active than NFG in causing potassium efflux from normal erythrocytes, as well as in killing the malaria parasite, supports the hypothesis that peptideinduced parasite death is related to their capacity to induce potassium leakage from infected erythrocytes. Finally, the observation that erythrocytes are able to restore their normal ion contents after losing more than 50% of their potassium content by incubation with NFG or gramicidin, suggests that, in vivo, and upon treatment with drug concentrations that cause full inhibition of parasite growth, these cells would not be irreversibly damaged by action of the drugs.     

Enhancement of leaf nitrogen,phosphorus and potassium and seed protein in Vigna radiata by pyridoxine application

Soaking the seeds of mungbean (Vigna radiata L. Wilczek cv. K-851) in pyridoxine solution significantly enhanced leaf N, P and K concentrations at different growth stages, and seed protein concentration at harvest. Leaf N, P and K were significantly correlated with root length and seed protein. Thus, pyridoxine application not only enhanced the availability of nutrients to plants but also was responsible for the maintenance of a favourable source-sink relationship, thus ensuring more nutritious seeds of mungbean.     

Effects of different nitrogen forms and combination with foliar spraying with 6-benzylaminopurine on growth,transpiration, and water and potassium uptake and flow in tobacco

NH₄ ⁺-N can have inhibitory effects on plant growth. However, the mechanisms of these inhibitory effects are still poorly understood. In this study, effects of different N forms and a combination of ammonium + 6-benzylaminopurine (6-BA, a synthetic cytokinin) on growth, transpiration, uptake and flow of water and potassium in 88-days-old tobacco (Nicotiana tabacum L. K 326) plants were studied over a period of 12 days. Plants were supplied with equal amounts of N in different forms: NO₃ ^–, NH₄NO₃, NH₄ ⁺ or NH₄ ⁺+6-BA (foliar spraying every 2 days after onset of the treatments). For determining flows and partitioning upper, middle and lower strata of three leaves each were analysed. During the 12 days study period, 50% replacement of NO₃ ^–-N by NH₄ ⁺-N (NH₄NO₃) did not change growth, transpiration, uptake and flow of water and K⁺ compared with the NO₃ ^–-N treatment. However, NH₄ ⁺-N as the sole N-source caused: (i) a substantial decrease in dry weight gain to 42% and 46% of the NO₃ ^–-N and NH₄NO₃ treatments, respectively; (ii) a marked reduction in transpiration rate, due to reduced stomatal conductance, illustrated by more negative leaf carbon-isotope discrimination (¹³C) compared with the NO₃ ^– treatment, especially in upper leaves; (iii) a strong reduction both in total water uptake, and in the rate of water uptake by roots, likely due to a decrease in root hydraulic conductivity; (iv) a marked reduction of K⁺ uptake to 10%. Under NH₄ ⁺ nutrition the middle leaves accumulated 143%, and together with upper leaves 206% and the stem 227% of the K⁺ currently taken up, indicating massive mobilisation of K⁺ from lower leaves and even the roots. Phloem retranslocation of K⁺ from the shoot and cycling through the root contributed 67% to the xylem transport of K⁺, and this was 2.2 times more than concurrent uptake. Foliar 6-BA application could not suppress or reverse the inhibitory effects on growth, transpiration, uptake and flow of water and ions (K⁺) caused by NH₄ ⁺-N treatment, although positive effects by 6-BA application were observed, even when 6-BA (10^–8 M) was supplied in nutrient solution daily with watering. Possible roles of cytokinin to regulate growth and development of NH₄ ⁺-fed plants are discussed.     

钾肥及与秸秆配施对紫色土作物产量和微生物群落结构的影响

基于紫色菜园土壤莴笋-白菜-甜玉米轮作4年12季连续定位施钾肥试验,研究不同种类钾肥及用量对重庆地区紫色菜园土上作物产量和土壤微生物群落结构的影响,为该地区作物生产确定合理的施钾技术提供科学依据。结果表明,在施用氮磷肥基础上,不同钾肥处理莴笋、白菜、甜玉米产量均显著提高;从3种作物4年平均产量和钾肥效益看,以单施适量化学钾(K_2)、单施适量秸秆钾(M_2)和秸秆还田配施少量化学钾(K_1+M_1)的施钾肥模式对白菜的增产效果好,增产28.05%—30.27%;M_2和K_1+M_1施钾肥模式对莴笋的增产效果较好,增产13.89%和13.81%;K_1+M_1施钾肥模式对甜玉米的增产效果最好,增产15.10%,表明秸秆还田配施少量化学钾(K_1+M_1)模式在供试3种作物生产中具有很好的应用前景。不同施钾处理对土壤微生物群落结构及丰度均会产生一定影响,以秸秆还田配施少量化学钾肥(K_1+M_1)对提高土壤细菌、真菌、革兰氏阳性菌的作用较好,并显著增加土壤微生物总PLFA含量,缓解对土壤微生物生存环境的胁迫,说明K_1+M_1能为土壤微生物的生长繁育创造有利环境。莴笋、白菜、甜玉米3种作物4年平均产量与土壤细菌、真菌、革兰氏阳性菌和革兰氏阴性菌数量间存在显著相关性(P0.05),而不同钾肥处理对土壤微生物特征具有一定影响,说明施钾肥可能会调节土壤微生物特征,从而促进作物增产。