A transgenic approach to enhance phosphorus use efficiency in crops as part of a comprehensive strategy for sustainable agriculture

Concerns about phosphorus (P) sustainability in agriculture arise not only from the potential of P scarcity but also from the known effects of agricultural P use beyond the field, i.e., eutrophication leading to dead zones in lakes, rivers and coastal oceans due to runoffs from fertilized fields. Plants possess a large number of adaptive responses to P_i (orthophosphate) limitation that provide potential raw materials to enhance P_i scavenging abilities of crop plants. Understanding and engineering these adaptive responses to increase the efficiency of crop capture of natural and fertilizer P_i in soils is one way to optimize P_i use efficiency (PUE) and, together with other approaches, help to meet the P sustainability challenge in agriculture. Research on the molecular and physiological basis of P_i uptake is facilitating the generation of plants with enhanced P_i use efficiency by genetic engineering. Here we describe work done in this direction with emphasis on the up-regulation of plant proton-translocating pyrophosphatases (H⁺-PPases).     

投碱种类和氨吹脱对污泥碱性发酵产酸的影响

采用完全混合式厌氧反应器,比较了NaOH和Ca(OH)2 2种碱试剂对污泥厌氧发酵产酸的作用效果,结合氨吹脱作用考察了NH4+浓度的降低对各有机物水解酸化程度的影响.结果表明在pH值为10的条件下,以NaOH调节的体系中各种有机物尤其是挥发性脂肪酸(VFAs)的量明显高于以Ca(OH)2调节的体系.Ca(OH)2调节的体系中释放出的蛋白质有部分沉淀,磷酸盐含量也较低,小于40mg/L;氨吹脱的体系发酵液中氨氮含量减少了43%,增大了VFAs的积累量;在NaOH和氨吹脱的组合条件下,污泥水解酸化程度最好,SCOD为6732mg/L,蛋白质为2029mg/L,碳水化合物374mg/L,VFAs总量2545mg/L,且氨氮含量低于200mg/L;分析认为氨吹脱作用增大VFAs积累量的原因主要是NH4+浓度的减小,促进了产酸菌对于碳水化合物的发酵.     

Effects of humic acid on residual Al control in drinking water treatment plants with orthophosphate addition

This study aimed to investigate the effects of humic acid (HA) on residual Al control in drinking water facilities that used orthophosphate addition. The results showed that adding orthophosphate was an effective method for residual Al control for the raw water without HA. When orthophosphate was added at 1.0 min before the addition of poly aluminum chloride (PACl), the concentrations of soluble aluminum (Sol-Al) and total aluminum (Tot-Al) residue were 0.08 and 0.086 mg·L^-1, respectively; both were reduced by 46% compared with the control experiment. The presence of HA would notably increase the residual Al concentration. For the raw water with 5 mg·L^-1 of HA, the concentrations of Sol-Al and Tot-Al increased from 0.136 and 0.174 mg·L^-1 to 0.172 and 0.272 mg·L^-1, respectively. For water with a HA concentration above 5 mg·L^-1, orthophosphate was ineffective in the control of residual Al, though there were still parts of orthophosphate were removed in coagulation. The amounts of Al removal were positively correlated with the solids freshly formed in coagulation. Similar to the raw water without HA, the best Al control was obtained with orthophosphate salt added at 1.0 min before PACl. HA concentrations in the raw water, solution pH, and the orthophosphate dosage suitable for residual Al control by orthophosphate precipitation were also investigated.