Influence of air porosity on distribution of gases in soil under assay for denitrification

 There has been concern that the measurement of gas emissions from a soil surface may not accurately reflect gas production within the soil profile. But, there have been few direct assessments of the error associated with the use of surface emissions for estimating gas production within soil profiles at different water contents. To determine the influence of air porosity on the distribution of gases within soil profiles, denitrification assays were performed using soil columns incubated with different water contents to provide air porosities of 18%, 13%, and 0% (equivalent to 62%, 73%, and 100% water-filled pore space, respectively). The soil columns were formed by packing sieved soil into cylinders which could be sealed at the top to form a headspace for the measurement of surface emissions of soil gases. Gas-permeable silicone tubing was placed at three depths (4.5, 9, and 13.5 cm) within each soil core to permit the measurement of gas concentration gradients within the soil core. Assays for denitrification were initiated by the addition of acetylene (5 kPa) to the soil column, and gas samples were taken from both the headspace and gas-permeable tubing at various times during a 46-h incubation. The results showed that at 18% air porosity, the headspace gases were well equilibrated with pore-space gases, and that gas emissions from the soil could provide good estimates of N₂O and CO₂ production. At air porosities of 13% and 0%, however, substantial storage of these gases occurred within the soil profiles, and measurements of surface emissions of gas from the soils greatly underestimated gas production. For example, the sole use of N₂O emission measurements caused three to five fold underestimates of N₂O production in soil maintained at 13% air porosity. It was concluded that the confounding influence of soil moisture on gas production and transport in soil greatly limits the use of surface emissions as a reliable indicator of gas production. This is particularly pertinent when assessing processes such as denitrification in which N gas production is greatly promoted by the conditions that limit O₂ influx and concurrently limit N gas efflux. Received: 15 January 1999     

粪产碱菌耐铵工程菌与水稻联合共生固氮作用

粪产碱菌（ Ａａｅｃａｌｉｓｆａｅｃａｌｉｓ） 在ＬＷ 培养基下能产生植物激素ＩＡＡ。盆栽结果表明,接种Ａ．ｆａｅｃａｌｉｓ 显著提高了水稻的生长,接种Ａ１５０１ 和Ａ１５１３ 的水稻稻谷产量分别比未接种提高了８５％ 和１０３ ％ ,用１５ Ｎ 同位素稀释法估测水稻地上部总氮中来源联合固氮的百分率达９００ ％ 和１１５ ％ ,其结果与水稻地上部（ 茎叶及稻谷） 总氮量的增加幅度（８６ ％ 和１１６ ％ ）基本一致。研究还表明Ａ１５１３ 耐铵工程菌的产ＩＡＡ作用以及对水稻的生长和产量、联合固氮作用均优于原始菌株Ａ１５０１ 。     

诱变处理后幼苗碳素养分合成及其运转

运用１４ Ｃ标记示踪技术,测定诱变处理后幼苗的光合作用、呼吸作用,并考查碳素营养运转情况,结果表明：不同处理对光合作用影响很小,但呼吸作用随复合剂量加大而增加,同时输出物质减少。     

氮钾营养对春玉米后期碳氮代谢与粒重形成的影响

 采用田间试验与生化分析等方法研究不同氮钾用量下春玉米后期碳氮代谢与粒重形成的关系。结果表明,适宜氮钾用量下,玉米叶片可溶蛋白含量较高,RuBP羧化酶和PEP羧化酶活性较强,收获指数与氮收获指数较高。适宜的氮钾用量可促进玉米营养体碳氮向籽粒运输,同时提高生长后期叶片的光合能力及根系的氮素吸收。     

不同熟期小麦品种收获指数（HI）的遗传研究

采用Ｃｒｉｆｆｉｎｇ方法Ｉ,利用６×６完全双列杂交,对不同熟期冬小麦品种收获指数（ＨＩ）的遗传机制进行了初步探讨。结果表明：ＨＩ的ＧＣＡ效应、ＳＣＡ效应和Ｒ效应均达到极显水平,其均方比为１．８０４：０．３８４：１;ＨＩ遗传以加性基因效应占优势,但反交效应和非加性基因效应也不可忽视;加性基因效应对后代ＨＩ的提高因亲本而异,在该性状的遗传改良中存在着母体效应;ＨＩ的广义遗传力的９２．４４％,狭义遗传     

不同苜蓿品种主根受伤后同工酶变化

研究根系发育能力不同的苜蓉品种在主根受到伤害时同工酶的变化规律,结果表明,主根受伤前,根系发育能力强、中和弱的无棣、陇东和北疆苜蓿,处理与对照间脂酶和超氧化物歧化酶同工酶无明显差异,根组织脂酶同工酶的酶带数多于叶片。根组织和叶片超氧化物歧化酶同工酶的酶带数相同。主根受伤后,无棣和陇东苜蓿根组织脂酶同工酶的酶带数均比对照多１２上,但二者的变化方式不同。无棣苜蓿叶片脂商工酶的酶带数我于对照,无棣和陇东     

优质籼型不育系浙农8010A的选育与应用

不育系浙农 ８０１０ Ａ 育性败育彻底、开花习性好、异交率高、配合力强,尤其是其低直链淀粉含量对改善杂交籼稻的米质有广阔的应用前景。     

盐度和饵料对中国对虾碳收支的影响_

通过内生长实验的方法测定了中国对虾在不同盐度下摄食日本刺沙蚕及盐度３１海水中摄食日本棘少蚕和配合饲料的碳收支。结果显示,盐度５－３５范围内,水温２５℃时,对虾的碳摄食量在盐度１３时达到最大为６１．６４;而最适生长的盐度条件为２０,此时的碳利用效率最高为２５．８４％,碳的特定生长率最大为３．８９％。     

莲子草假隔链格孢在不同条件下的生长和产孢能力

莲子草假隔链格孢(Nimbyaalternantherae)在PDA、PCA、NBA、CMA、MA、ZA、GA、OA、Czapek和“组织煎汁”等10种培养基上均能生长;在PCA上产孢最多,而在Czapek培养基上不能产孢病菌经回接后从病茎再分离,产孢能力可提高1倍多病菌在30℃下生长最快,25℃下产孢量最大,15℃下则不产孢全光照(3000lx)可促进菌丝生长,但会抑制产孢     

烤烟亲本配合力及杂种优势分析

选用７ 个烤烟品种按双列杂交设计配成２１ 个杂交组合－ 估算了７ 个亲本６ 个性状的配合力和４ 个性状的杂种优势率－ 结果表明,６ 个性状的一般配合力,４ 个性状的特殊配合力均达到了极显著水平－ 亲本间和杂交组合间表现出较大的差异,亲本以３１７,株４－ １ 表现最好,其次是红大和ＮＣ８２ ,Ｃ２ 表现最差;组合以株４ － １ ×３１７,３１７ ×红大,３１７ ×Ｋ３２６ ,ＮＣ８２ ×红大表现较好－