Differences in mycorrhizal infection and P uptake of sweet potato cultivars (Ipomoea batatas L.) during their early growth in three soils

Summary Mycorrhizal infection in the roots of 10 sweet potato cultivars was assessed 7 weeks after planting in three soils collected from Ibadan, Fashola and Onne in southern Nigeria, three soils which contained 21.0, 7.8 and 54.8 mg P kg^–1, respectively. Mycorrhizal infection averaged 17% in the soil from Ibadan, 24% in the soil from Fashola and 7% in the acid soil from Onne. The plants grown in the Fashola soil contained the same percentage of P as plants grown in the Onne soil. Although the percentage of P in sweet potato was lowest in the Ibadan soil, shoot dry weights were 35% higher in this soil than in the other two soils. There was no correlation between the level of mycorrhizal infection and plant dry weight in the partially sterilized soil from Ibadan. Sweet potato inoculated in this soil with infected roots of Leucaena leucocephala showed a higher level of mycorrhizal infection than uninoculated plants. Dry-matter production was, however, the same for all treatments. The sweet potato cultivars differed in their level of mycorrhizal infection and in their response to applied P. Cultivars TIS 2498 and TIS 70357 consistently showed the lowest percentage of infection; and TIb 4, TIS 8441 and TIS 8524 showed infection levels above 20% in the Fashola and Ibadan soils. When the low-yielding cultivar, TIb 4, and an improved clone, TIS 9265, were grown in the presence of 50 and 100 mg single superphosphate per kg soil, TIb 4 produced more dry matter in the presence of P fertilizer than it did without the fertilizer. Growth and mycorrhizal infection of TIS 9265 were not affected by the fertilizer.     

Dietary cation–anion difference and cadmium concentration in grasses fertilized with chloride

High dietary cation–anion difference (DCAD) of grass herbage increases the occurrence of hypocalcaemia of dairy cows. Application of chloride fertilizer reduces DCAD of herbage but it could increase cadmium concentration in herbage. This study includes an experiment conducted in Australia and in Canada. A glasshouse experiment in Australia evaluated the effect of four rates of chloride application (0–240 kg ha^?1) on values of herbage DCAD and cadmium concentration of above‐ground plant material of timothy (Phleum pratense L.) and phalaris (Phalaris aquatica L.), harvested 6 weeks after sowing and grown on two soils that had received cadmium either as a contaminant in superphosphate (soil + Super) or in sewage biosolids (soil + Bio) along with respective control soils (soil 0 Super and soil 0 Bio). Application of chloride fertilizer decreased values of herbage DCAD by 349 mmol_c kg^?1 dry matter (DM). Herbage DCAD values were highest on the 0 Bio soil (739 mmol_c kg^?1 DM) and were not different among the three other soils. Species did not differ in herbage DCAD values. Cadmium concentration in the above‐ground plant material was highest on the +Bio soil treatment (1·67 mg kg^?1 DM) and was lower for the three other soil treatments. Above‐ground plant material of phalaris had a higher cadmium concentration than that of timothy. Application of chloride fertilizer did not affect cadmium concentration in above‐ground plant material, despite the high cadmium content of the soil on the +Bio treatment. The field experiment in Canada evaluated the effect of four rates of chloride application (0–144 kg ha^?1) on cadmium concentration of a timothy‐based grass sward grown on four sites with soils of different potassium content. Application of chloride fertilizer increased cadmium concentration of herbage at two of the four sites but the maximum increase in cadmium concentration was only 0·025 mg kg^?1 DM. Chloride fertilizer can be applied to decrease forage DCAD with minimal risk of increasing Cd in the food chain.     

不同氨氮浓度对水蕹菜生长特性的影响

[目的]探讨不同氨氮浓度对水蕹菜生长特性的影响。[方法]通过在营养液中设置不同氨氮浓度(0、0.1、0.5、1.0、5.0、10.0、50.0 mg/L),对优良的水面培植作物——水蕹菜扦插苗展开培养,研究其各项生长指标对氨氮浓度变化的响应及其对氨氮的吸收利用。[结果]氮素缺乏导致水蕹菜植株增高减缓,叶片黄化,分蘖受抑。当氨氮浓度超过0.5 mg/L时,植物快速增高;但超过10.0 mg/L,又会抑制植株增长,根系溃烂,叶片脱落。氨氮初始浓度为1.0 mg/L时,水蕹菜各项生长指标最优,对氨氮净化效率最大,为96.3%。氨氮浓度超过1.0 mg/L时,植株根长偏短,根重偏低,茎叶系统增重明显,总生物量增长状况优于低氨氮处理(1.0 mg/L),但净化效率却随着氨氮浓度的增加而下降。[结论]该研究为鱼虾菜生态养殖模式的推广应用提供了理论依据。     

美国紫薯试管苗微型繁殖的研究

为满足人们对经过热处理的美国紫薯试管苗种苗的大量需求,以微型嫩茎段为材料,采用组织培养和微型扦插的方法,进行了试管苗微型繁殖的研究。结果表明：在1/2MS＋IAA0．2 mg?L‐1＋蔗糖15 g?L‐1培养基上,以具有2个生长点和2个叶片的微型茎段繁殖试管苗,1株试管苗每年能繁殖200多万株试管苗;以具有2个生长点和2个叶片的苗微型茎段扦插到苗床上,其繁殖速度提高了1．8倍。定植的微型扦插试管苗生长较旺盛,美国紫薯的产量提高48．9％。     

Phytoaccumulation of Lead by Selected Wetland Plant Species

Several anthropogenic activities lead to the production of substantial amounts of aqueous effluents that contain various toxic trace and heavy metals and which pose potential threats to the wild habitat of wetlands. As a part of the remediation of heavy metals, it is necessary to identify some aquatic hyperaccumulator plants. To this end, a greenhouse study was conducted to investigate the phytotoxicity resulting from lead (Pb) and its accumulation in selected plant species. Lead was added from low to very high levels in a swell–shrink clayey soil (Typic Haplustert). Seven levels of Pb (0, 50, 100 200, 400, 600, and 800 mg kg^–1 soil) were applied. Typha angustifolia L. of Typhaceae and Behaya plant (Ipomoea carnea L.) of the Convolvulaceae family were taken as test plants. Lead was added at high and low concentrations to determine whether an increase in concentration would Pb to an increased toxicity to the plants. Recorded weight of the Typha crop was reduced (6%) at 600 mg Pb kg^–1 soil, and at greater doses of Pb, the dry-matter yield was inhibited considerably. In the case of Ipomoea, no growth retardation from Pb was observed. Most Pb accumulated in roots and then was transported to shoots. The Typha angustifolia L. and Ipomoea carnea L. plants show promise for the removal of Pb from contaminated wastewater because they can accumulate high concentrations of Pb in roots (1200 and 1500 mg Pb kg^–1 respectively) and shoots (275 and 425 mg Pb kg^–1 respectively). Lead uptake by both the plants increased with the increasing doses of Pb (50 to 800 mg kg^–1 soil). Physiological parameters such as photosynthesis, respiration, chlorophyll content, and different enzyme activities including nitrate reductase (NR), peroxidase (POD), and succinate dehydrogenase (SD) were also studied for the evaluation of these plant species. In Typha plants, at greater doses of Pb, the rate of photosynthesis and chlorophyll content decreased whereas POD and SD activities increased to combat oxidative stress.     

Nitrogen rate and cultivar effects on nitrogen and nitrate concentration of sweet potato leaf tissue

Abstract

Nitrogen applications to dallisgrass grown on Olivier silt loam, an Aquic Fragiudalf, increased forage yield, forage digestibility, nutrient concentrations and nutrient contents as N rates increased to 896 kg ha^‐1. Expressing yield as a function of N application rate resulted in quadratic prediction equations that accounted for 75 to 98% of the variability in yield during five years. Eighty‐six percent of the maximum yield was obtained during the five years at 448 kg of N ha^‐1. Plant concentrations of N, Ca and Mg were increased more than concentrations of the other macronutrients as N rates increased. Plant contents of N, Ca and Mg in the forage increased 4.0, 3.2 and 3.5‐fold as N rates increased to 448 kg ha^‐1, while that of P, K and S increased 2.5 to 2.8‐fold. Residual N accumulations in the soil profile were apparent at the 896 kg ha^‐1 rate at the end of the growing seasons but were not detected the following March, indicating N losses by leaching and/or denitrification occurred at that N rate. Phosphorus applications increased forage P concentrations but did not increase forage yield nor available P levels in the surface 15 cm of soil. Maximum yields were obtained at forage P concentrations and Bray No. 2 soil P levels as low as 2.0 g kg^‐1 and 17 mg kg^‐1, respectively.     

生物炭和猪粪肥对铜污染土壤中蕹菜生长及铜形态的影响

采用盆栽试验研究了5%质量的生物炭、5%猪粪肥单独或联合施用于外源Cu污染(0、200、400 mg·kg~(-1))土壤,对蕹菜生长和5种形态Cu含量(Tessier提取法)的影响。结果表明:在养分含量不高的Cu污染红壤中,施用猪粪肥能够显著提高蕹菜生物量(平均比CK提高56.4%),并促进蕹菜对Cu的吸收和累积;施用生物炭能降低蕹菜含铜量(平均比CK降低21.1%);单施猪粪肥或联合施用(5%猪粪肥+5%生物炭)的蕹菜含铜量比对照(CK)分别增加了40.2%、31.7%(200 mg·kg~(-1))和27.5%、38.8%(400 mg·kg~(-1));未添加外源Cu污染时,土壤中铜的有机结合态铁锰氧化态碳酸盐结合态可交换态;各形态Cu含量随处理不同差异显著,其中单施猪粪肥的土壤中可交换态和有机物结合态Cu、单施生物炭的土壤中有机物结合态Cu、二者混施的土壤中碳酸盐结合态和有机物结合态Cu与其他形态Cu含量相比均有明显增长的趋势。联合施用猪粪肥及生物炭处理的蕹菜生物量虽比单施猪粪肥的蕹菜生物量略有降低,但与单施猪粪肥相比,钝化土壤重金属的作用明显。     

基于银川地区水质的空心菜营养液配方验证试验

采用深液流(DFT)无土栽培技术,在优选出空心菜水培营养液配方的基础上,于二代节能日光温室内进一步研究验证了NO3-N、P、K、Ca四种元素对空心菜生长势、产量、品质及全氮、全磷及全钾含量的影响。结果表明:采用优选的最佳配方栽培的空心菜,其生长势、根系活力、产量、品质以及全氮磷钾含量均相对高于对照。基于宁夏银川地区水质的水培空心菜NO3-N、P、K、Ca四种元素的最优配方为:9、0.5、4.54、.0 mmol/L。     

密度和收割对水蕹菜净水效果的影响

通过在水桶试验中设置2种不同处理方式(密度和收割),研究水蕹菜(Ipomoea aquatic Forsk)对富营养水质的净化特性及效果。结果表明:室外培养12 d,高密度组(10 g/L)对NO2-、NO3-、PO32-、TN、TP和Chl-a的平均去除率最高,分别为90.88%、93.98%、98.96%、82.36%、88.89%和89.33%,显著高于对照组(0 g/L);收割有助于刺激植物加速分蘖、促进植物对N、P元素的吸收固定,并改善水体的DO;水蕹菜组织N、P含量在试验前后发生变化,并与生长水体中的N、P浓度呈正相关关系;植物固定对水体中N、P去除的贡献率与植菜密度呈正相关关系,占高密度组水体中TN、TP去除总量的52.05%和40.41%,为试验组水体中N、P去除的主要途径。     

优良乳酸菌的筛选及对腌制茭白品质的影响

为获得最适腌制茭白启动发酵剂,缩短腌制茭白生产周期、提高质量品质,从分离筛选保藏的4种乳酸菌菌株(植物乳杆菌、短乳杆菌、嗜柠檬酸明串球菌和戊糖片球菌)中优选出植物乳杆菌和戊糖片球菌2种优良乳酸菌,采用5种不同配比方式分别接种发酵,研究茭白腌制过程中p H、酸度、亚硝酸盐和微生物指标的变化,并对成品的色泽、质地和挥发性风味物质进行分析。结果表明,配比方式对茭白腌制过程中p H、酸度、乳酸菌数和细菌总数的影响不大;在不同配比方式接种中,接种1%植物乳杆菌和2%戊糖片球菌复合菌作为茭白腌制发酵剂,其腌制茭白的"亚硝峰"值最小,为1.62 mg·kg-1,色泽与鲜茭白最为接近,质地口感最好;不同配比方式接种茭白腌制共检测出挥发性风味物质118种,1%植物乳杆菌和2%戊糖片球菌腌制的茭白成品所含风味物质种类和相对含量均较高。因此,最终确定的最佳发酵剂为1%植物乳杆菌和2%戊糖片球菌。本研究结果为茭白的腌制及干制加工的工业化生产提供了理论依据。