抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Soil Chemical Analysis

1. Plant Nutrients. 2. The Soil as a Plant Nutrient Medium. 3. Nutrient Uptake and Assimilation. 4. Plant Water Relationships. 5. Plant Growth and Crop Production. 6. Fertilizer Application. 7. Nitrogen. 8. Sulphur. 9. Phosphorus. 10. Potassium. 11. Calcium. 12. Magnesium. 13. Iron. 14. Manganese. 15. Zinc. 16. Copper. 17. Molybdenum. 18. Boron. 19. Further Elements of Importance. 20. Elements with More Toxic Effects. General Readings. References. Index.

/pdf/principles-of-plant-nutrition-2k4wl46ou6.pdf

Principles of plant nutrition

Reactive oxygen species (ROS) are produced as a normal product of plant cellular metabolism. Various environmental stresses lead to excessive production of ROS causing progressive oxidative damage and ultimately cell death. Despite their destructive activity, they are well-described second messengers in a variety of cellular processes, including conferment of tolerance to various environmental stresses. Whether ROS would serve as signaling molecules or could cause oxidative damage to the tissues depends on the delicate equilibrium between ROS production, and their scavenging. Efficient scavenging of ROS produced during various environmental stresses requires the action of several nonenzymatic as well as enzymatic antioxidants present in the tissues. In this paper, we describe the generation, sites of production and role of ROS as messenger molecules as well as inducers of oxidative damage. Further, the antioxidative defense mechanisms operating in the cells for scavenging of ROS overproduced under various stressful conditions of the environment have been discussed in detail.

https://downloads.hindawi.com/archive/2012/217037.pdf

Reactive Oxygen Species, Oxidative Damage, and Antioxidative Defense Mechanism in Plants under Stressful Conditions

http://directory.umm.ac.id/Data%20Elmu/jurnal/P/PlantScience/PlantScience_Elsevier/Vol151.Issue1.2000/5250.pdf

Oxidative stress and some antioxidant systems in acid rain-treated bean plants Protective role of exogenous polyamines

Increase in membrane permeability and exudation in roots of zinc deficient plants

Sixty-six spring and winter common wheat genotypes from Central Asian breeding programs were evaluated for grain concentrations of iron (Fe) and zinc (Zn). Iron showed large variation among genotypes, ranging from 25 mg kg−1 to 56 mg kg−1 (mean 38 mg kg−1). Similarly, Zn concentration varied among genotypes, ranging between 20 mg kg−1 and 39 mg kg−1 (mean 28 mg kg−1). Spring wheat cultivars possessed higher Fe-grain concentrations than winter wheats. By contrast, winter wheats showed higher Zn-grain concentrations than spring genotypes. Within spring wheat, a strongly significant positive correlation was found between Fe and Zn. Grain protein content was also significantly (P < 0.001) correlated with grain Zn and Fe content. There were strong significantly negative correlations between Fe and plant height, and Fe and glutenin content. Similar correlation coefficients were found for Zn. In winter wheat, significant positive correlations were found between Fe and Zn, and between Zn and sulfur (S). Manganese (Mn) and phosphorus (P) were negatively correlated with both Fe and Zn. The additive main effects and multiplicative interactions (AMMI) analysis of genotype × environment interactions for grain Fe and Zn concentrations showed that genotype effects largely controlled Fe concentration, whereas Zn concentration was almost totally dependent on location effects. Spring wheat genotypes Lutescens 574, and Eritrospermum 78; and winter wheat genotypes Navruz, NA160/HEINEVII/BUC/3/F59.71//GHK, Tacika, DUCULA//VEE/MYNA, and JUP/4/CLLF/3/II14.53/ODIN//CI13431/WA00477, are promising materials for increasing Fe and Zn concentrations in the grain, as well as enhancing the concentration of promoters of Zn bioavailability, such as S-containing amino acids.

Iron and zinc grain density in common wheat grown in Central Asia

Micronutrient malnutrition afflicts over three billion peopleworldwide and the numbers are continuously increasing. Developing genetically micronutrientenriched cereals, which are the predominant source of human dietary, is essential to alleviate malnutrition worldwide. Wheat chromosome 6B derived from wild emmerwheat [Triticum turgidum ssp. dicoccoides (Korn.) Thell] was previously reported to be a source for high Zn concentration in the grain. In the present study, recombinant chromosome substitution lines (RSLs), previously constructed for genetic and physical maps of Gpc-B1 (a 250-kb locus affecting grain protein concentration), were used to identify the effects of the Gpc-B1 locus on grain micronutrient concentrations. RSLs carrying the Gpc-B1 allele of T. dicoccoides accumulated on average 12% higher concentration of Zn, 18% higher concentration of Fe, 29% higher concentration of Mn and 38% higher concentration of protein in the grain as compared with RSLs carrying the allele from cultivated wheat (Triticum durum). Furthermore, the high grain Zn, Fe and Mn concentrations were consistently expressed in five different environments with an absence of genotype by environment interaction. The results obtained in the present study also confirmed the previously reported effect of the wild-type allele of Gpc-B1 on earlier senescence of flag leaves. We suggest that the Gpc-B1 locus is involved in more efficient remobilization of protein, zinc, iron and manganese from leaves to the grains, in addition to its effect on earlier senescence of the green tissues.

/pdf/multiple-qtl-effects-of-wheat-gpc-b1-locus-on-grain-protein-41itw1wlq7.pdf

Multiple QTL‐effects of wheat Gpc‐B1 locus on grain protein and micronutrient concentrations

The effect of phosphorus (P), potassium (K), and magnesium (Mg) deficiency on the development of leaf symptoms (chlorosis and necrosis) and activities of ascorbate-dependent H 2 O 2 scavenging enzymes (ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase) was studied in bean (Phaseolus vulgaris) plants over a 12 d period of growth in nutrient solution. With increasing plant age Mg- and K-deficient leaves developed severe interveinal chlorosis and, accordingly, chlorophyll concentrations were reduced. However, in P-deficient leaves neither chlorosis nor necrosis appeared; the leaves remained dark green and even at an advanced stage of P deficiency, chlorophyll concentrations were still higher than those of control plants

Activity of ascorbate-dependent H2O2-scavenging enzymes and leaf chlorosis are enhanced in magnesium- and potassium-deficient leaves, but not in phosphorus-deficient leaves

Nutrient availability in the rhizosphere differs in many respects from that in the bulk soil. Factors of major importance for the mineral nutrition of plants are root‐induced changes in rhizosphere pH, in reducing capacity of the roots, and in amount and composition of root exudates. These changes are in many instances root‐responses to the nutritional status of plants. Examples are given for zinc, iron, and phosphorus nutritional status in plants. Changes in nutrient availability in the rhizosphere may also be a consequence of alterations in the rhizosphere microflora. Root‐induced changes are important components for the adaptation of plants to extreme chemical soil conditions and for efficient use of soil and fertilizer nutrients.

Ismail Cakmak

Papers

Increase in membrane permeability and exudation in roots of zinc deficient plants

Iron and zinc grain density in common wheat grown in Central Asia

Multiple QTL‐effects of wheat Gpc‐B1 locus on grain protein and micronutrient concentrations

Activity of ascorbate-dependent H2O2-scavenging enzymes and leaf chlorosis are enhanced in magnesium- and potassium-deficient leaves, but not in phosphorus-deficient leaves

Root‐induced changes of nutrient availability in the rhizosphere