Effects of straw return with potassium fertilizer on the stem lodging resistance, grain quality and yield of spring maize (Zea mays L.).

This experiment aimed to study the effects of straw return combined with potassium fertilizer on stem lodging resistance, grain quality, and yield of spring maize. The objective was to provide a scientific basis for the rational utilization of Inner Mongolia spring maize straw and potassium fertilizer resources. The test material used was 'Xianyu 335', and the study was conducted in three ecological regions from east to west of Inner Mongolia (Tumochuan Plain Irrigation Area, Hetao Plain Irrigation Area, and Lingnan Warm Dry Zone). A split-plot design was employed, with the straw return method as the main plot and potassium fertilizer dosage as the secondary plot. We determined the stem resistance index, grain quality, and yield. The results showed that both straw return and potassium application improved stem lodging resistance, grain quality, and maize yield. Combining straw return with the reasonable application of potassium fertilizer enhanced the effectiveness of potassium fertilizer, increased lodging resistance, maize yield, and improved grain quality and yield stability. Under the straw return treatment, with potassium application compared to no potassium application, significant increases were observed in maize plant height, stem diameter, dry weight of stems, stem compressive strength, stem bending strength, grain protein content, yield, straw potassium accumulation content, and soil available potassium content. These increases were up to 30.79 cm, 2.63 mm, 15.40 g, 74.93 N/mm2, 99.65 N/mm2, 13.68%, 3142.43 kg/hm2, 57.97 kg/hm2, and 19.80 mg/kg, respectively. Therefore, the interaction of straw return and potassium fertilizer was found to be the most effective measure for maintaining high-yield and stress-resistant cultivation, improving grain quality, and optimizing the management of straw and potassium fertilizer resources. This approach is suitable for promotion and application in the spring maize growing areas of Inner Mongolia.

Potentials of straw return and potassium supply on maize (Zea mays L.) photosynthesis, dry matter accumulation and yield.

Maize (Zea mays L.) is considered one of the most important grains in the world. Straw return has the effect of reducing soil bulk density and increasing soil porosity. Straw returning and potassium fertilizer can supplement soil potassium content. The improvement of soil structure and the optimization of soil nutrient levels provide a good environment for high yield and high efficiency of maize. Therefore, three field experiments were carried out over a three-year period (2018-2020) to study the effects of straw returning on photosynthesis, dry matter accumulation and yield of maize 'Xianyu 335' under two different fertilization methods and four potassium application levels. The results showed that straw returning and potassium application had significant effects on the above indicators. The above indicators were significantly improved by deep tillage straw returning compared with no tillage straw returning. Increasing potassium supply can promote the effect of straw returning. The photosynthesis, dry matter accumulation and yield parameters of maize treated with straw returning and deep tillage combined with 60 kg/hm2 potassium fertilizer (SFK60) reached the highest in the three harvest seasons. The corn planting profit of SFK45 treatment is the highest, which is $1868.92 per ha. Therefore, SFK45 is an effective way to ensure stable and high yield of corn and maximize farmers' income.

[Genetic diversity of Pardosa pseudoannulata populations and its relationships with habitats].

A random amplified polymorphic DNA (RAPD) analysis was made on the Pardosa pseudoannulata populations collected from eight habitats in Central-south China, Southwest China, and Hainan Island. 10 from 50 primers were selected, and 84 bands of 200-2500 bp fragments were amplified, among which, 62 bands (73.8%) were polymorphic, suggesting an obvious polymorphism of the populations. As estimated by Shannon index, genetic similarity index and genetic distance, the total genetic diversity index of the spider was 0.5177, with the genetic variation being 64.24% within the P. pseudoannulata populations and 35.76% among the populations. The genetic distance among the eight populations ranged from 0.0753 to 0.3725, with an average of 0.2426, indicating that the eight populations engendered adaptive variations with different habitats. Multiple regression analysis showed that annual mean air temperature and pesticide application were the main factors restricting P. pseudoannulata to be a dominant insect species in rice field.

Role of the heme regulatory motif in the heme-mediated inhibition of mitochondrial import of 5-aminolevulinate synthase.

5-Aminolevulinate synthase (ALAS) is a mitochondrial enzyme that catalyzes the first step of the heme biosynthetic pathway. The mitochondrial import, as well as the synthesis, of the nonspecific isoform of ALAS (ALAS1) is regulated by heme through a feedback mechanism. A short amino acid sequence, the heme regulatory motif (HRM), is known to be involved in the regulatory function of heme. To determine the role of the HRM in the heme-regulated transport of the nonspecific and erythroid forms of ALAS in vivo, we constructed a series of mutants of rat ALAS1, in which the cysteine residues in the three putative HRMs in the N-terminal region of the enzyme were converted to serine ones by site-directed mutagenesis. The wild-type and mutant enzymes were expressed in quail QT6 fibroblasts through transient transfection, and the mitochondrial import of these enzymes was examined in the presence of hemin. Hemin inhibited the mitochondrial import of wild-type ALAS1, but this inhibition was reversed on the mutation of all three HRMs in the enzyme, indicating that the HRMs are essential for the heme-mediated inhibition of ALAS1 transport in the cell. By contrast, exogenous hemin did not affect the mitochondrial import of the erythroid-specific ALAS isoform (ALAS2) under the same experimental conditions. These results may reflect the difference in the physiological functions of the two ALAS isoforms.

[Researches on C-banding karyotypes of two species of Genus Eotmethis].

The chromosome C-banding technique has been employed in studying C-karyotypes of two grasshoppers species of Genus Eotmethis from Pamphagidae, namely, E. tiantsuensis and E. jintaiensis which are only distributed in Northwest China. Spermatogenous mitotic metaphases and primary spermatocyte meiotic metaphases (metaphase 1) of two species are analyzed. The main points of results are as follows. Either basic numbers of chromosomes (2n male symbol) and karyotypes formulae or centromeres location of two species are coincident with the preceding studies. These provide a further backing for the karyotype stability in the Pamphagidae. The corresponding values of chromosome relative length are closer between E. tiantsuensis and E.jintaiensis, and there are no obvious differences in their total C-heterochromatin contents, No.3, 4, 9 and X chromosomes of both species have showed larger and darkly stained acrocentric C-bands, and No.2 chromosomes of both species have consistently showed a distinct mid-stained interstitial C-band proximal to the median of chromosome. The above-metioned facts reflect a close relation between the two species in their systematic development. In addition, the differences in the C-banding patterns between two species are reflected more or less in No.1, No.7 and No.8 chromosomes, especially obvious variations in the size and stained degree of acrocentric C-blocks of corresponding No.7 and No.8 chromosomes between the two species.