不同甘氨酸浓度对无菌水培番茄幼苗生长和氮代谢的影响

植物不但能吸收矿质氮(NH+4-N、NO-3-N),而且也能直接吸收有机态氮,如氨基酸、小分子蛋白质等.为探讨有机态氮浓度对番茄幼苗生长和氮代谢的影响,无菌水培条件下采用2个番茄品种(申粉918、沪樱932)设置4种不同浓度(0、1.5、3.0、6 0mmol·L-1)的甘氨酸态氮(Gly-N),研究了番茄幼苗干物质重、吸氮量、氮代谢相关产物和氮代谢关键酶活性.结果表明,无菌水培条件下,随营养液中Gly浓度的增加,番茄植株干物质重、总氮量、地上部和根系游离氨基酸、可溶性蛋白、地上部可溶性糖含量增加.与无氮对照相比,各处理均显著降低了番茄地上部淀粉含量(P<0.05),而Gly浓度对根系淀粉含量无显著影响.随营养液中Gly浓度的增加,番茄地上部和根系的硝酸还原酶(NR)、谷氨酸脱氢酶(NADH-GDH)、丙转氨酶(GPT)和谷草转氨酶(GOT)活性均提高.无氮对照的NR活性与1.5 mmol·L-1 Gly处理之间差异不显著,而与3.0 mmol·L-1和6.0 mmol·L-1 Gly两处理之间差异显著(P<0.05);1.5 mmol·L-1 Gly和3.0 mmol·L-1 Gly两个处理之间的地上部NADH-GDH、GPT和GOT活性差异不显著.Gly浓度与番茄植株干物质重、总氮量呈显著正相关(R2>0.905* *),这表明两个番茄品种均能直接吸收利用甘氨酸.沪樱932吸收Gly的能力显著大于申粉918(P<0.05).因此,Gly-N可以成为番茄生长的良好氮源,其生理效应受Gly浓度的影响;不同品种番茄对Gly的吸收利用能力不同.     

镧胁迫下外源H2O2对裸燕麦幼苗叶绿素荧光参数和光合碳同化酶活性的影响

稀土污染已成为制约农业发展的一种重要因素,为探讨外源过氧化氢(H_2O_2)缓解裸燕麦镧(La)胁迫伤害的光合生理机制,以‘白燕7号’裸燕麦幼苗为材料,采用砂培方法,研究了5 mmol/L H_2O_2喷施预处理对1.20 mmol/L La~(3+)胁迫下裸燕麦幼苗生长、叶片叶绿素荧光参数和碳同化关键酶活性的影响。结果表明:La胁迫下,H_2O_2预处理的裸燕麦幼苗根长、株高和生长量的降幅及叶片叶黄素循环脱环氧化状态(A+Z)/(V+A+Z)显著下降,PSⅡ最大光化学效率(F_v/F_m)、实际光化学效率(Φ_(PSⅡ))、光化学猝灭系数(qP)和吸收光能用于光化学反应的份额(P)显著提高,PSⅡ非光化学猝灭系数(NPQ)、调节性能量耗散Y(NPQ)、非调节性能量耗散Y(NO)、吸收光能用于天线热耗散的份额(D)、PSⅡ反应中心非光化学耗散的份额(E_x)和双光系统间激发能分配不平衡偏离系数(β/α-1)明显降低,同时1, 5-二磷酸核酮糖羧化酶(Rubisco)、1, 7-二磷酸景天庚酮糖酯酶(SBPase)和1, 6-二磷酸果糖醛缩酶(FBAase)活性显著提高,但转酮醇酶(TKase)活性无显著变化。表明外源H_2O_2能够通过提高PSⅡ光化学效率和碳同化关键酶活性而非依赖叶黄素循环的热耗散来减轻La胁迫导致的光抑制,从而缓解La胁迫幼苗生长的受抑程度,增强裸燕麦对La胁迫的适应性。     

秸秆覆盖与施磷对西南冬小麦叶肉导度和CO2同化效率的影响

为探究西南麦区冬小麦旗叶叶肉导度(g_m)与CO₂同化对土壤速效磷缺乏的响应。试验于2020-2022年在四川仁寿试验站进行秸秆覆盖和磷素水平的二因素裂区试验,以秸秆覆盖(SM)和不覆盖(NSM)为主区;三个磷水平0(P0)kg/hm²、75(P75)kg/hm²和120(P120)kg/hm²为裂区,分析小麦旗叶光响应曲线、叶肉导度和CO₂同化对旗叶磷素水平的响应。结果表明:与NSM相比,SM下旗叶比叶重(LMA)、单位面积磷含量(PA)、单位质量磷含量(PM)和净光合速率(P_n)分别提高4.1%、16.9%、12.2%和6.9%,且随着施磷量的增加,旗叶的LMA、PA、PM和P_n呈增加趋势。秸秆覆盖与施磷显著提高旗叶最大净光合速率(P_nmax)和表观量子效率(AQY),增加旗叶的光合潜能。施磷显著提高旗叶光系统II实际光化学效率(ΦPSII),最大羧化效率(V_cmax)、核酮糖-1,5-二磷酸羧化酶(Rubisco)活力、胞间CO₂浓度(C_c)、叶绿体CO₂浓度(C_c)、气孔导度(g_s)和g_m,P75和P120较P0分别提高16.8%-23.8%、27.9%-35.3%、30.9%-61.7%、1.4%-3.6%、4.8%-13.1%、9.0%-10.2%和16.0%-16.9%,P75和P120无显著差异。秸秆覆盖与施磷降低旗叶的气孔限制(L_s)和叶肉限制(L_m),生化限制(L_b)是光合速率的主要限制因子。综上所述,秸秆覆盖配施75kg/hm²磷肥可提高西南冬小麦旗叶磷素含量、光系统II实际光化学效率、叶肉导度和CO₂同化效率,降低气孔限制和叶肉限制,从而提高旗叶净光合速率。     

高效降解甲醛菌株的分离鉴定及其特性

首先对新分离的、能高效降解甲醛的两菌株A1和A2在形态学特征、生理生化特性及16S rDNA序列分析等方面进行了系统研究; 随后通过测定在液体培养过程中甲醛浓度的变化, 确定新分离菌株A1、A2降解溶液中甲醛的性能; 最后利用菌株A1、A2分别进行生物填料塔的挂膜实验, 确定其对甲醛气体的净化性能。结果表明: 菌株A1属于假单胞菌属(Pseudomonas), 菌株A2为鞘氨醇单胞菌属(Sphingomonas); 当甲醛初始浓度<1 200 mg/L时,菌株A1、A2都能完全降解溶液中的甲醛, 当甲醛浓度增高至1 600 mg/L时, 菌株A1在48 h后的甲醛降解率为50%, 菌株A2在104 h后的甲醛降解率为74.3%; 菌株A1、A2对甲醛气体的净化效率均能达到99%以上, 菌株A1的甲醛生化去除量能达到26.4 mg/(L?h), 菌株A2的甲醛生化去除量可达20.6 mg/(L?h)。     

Assessing the response of forest productivity to climate extremes in Switzerland using model–data fusion

The response of forest productivity to climate extremes strongly depends on ambient environmental and site conditions. To better understand these relationships at a regional scale, we used nearly 800 observation years from 271 permanent long‐term forest monitoring plots across Switzerland, obtained between 1980 and 2017. We assimilated these data into the 3‐PG forest ecosystem model using Bayesian inference, reducing the bias of model predictions from 14% to 5% for forest stem carbon stocks and from 45% to 9% for stem carbon stock changes. We then estimated the productivity of forests dominated by Picea abies and Fagus sylvatica for the period of 1960–2018, and tested for productivity shifts in response to climate along elevational gradient and in extreme years. Simulated net primary productivity (NPP) decreased with elevation (2.86 ± 0.006 Mg C ha^?1 year^?1 km^?1 for P. abies and 0.93 ± 0.010 Mg C ha^?1 year^?1 km^?1 for F. sylvatica). During warm–dry extremes, simulated NPP for both species increased at higher and decreased at lower elevations, with reductions in NPP of more than 25% for up to 21% of the potential species distribution range in Switzerland. Reduced plant water availability had a stronger effect on NPP than temperature during warm‐dry extremes. Importantly, cold–dry extremes had negative impacts on regional forest NPP comparable to warm–dry extremes. Overall, our calibrated model suggests that the response of forest productivity to climate extremes is more complex than simple shift toward higher elevation. Such robust estimates of NPP are key for increasing our understanding of forests ecosystems carbon dynamics under climate extremes.     

华北丽斑麻蜥食物同化和疾跑速的热依赖性

作者研究山西阳泉丽斑麻蜥(Eremias argus)成体的选择体温、热耐受性及食物同化和疾跑速的热依赖性。选择体温、临界低温和临界高温无显著的两性差异,分别为36·0℃、1·0℃和44·9℃。在实验温度范围内,体温显著影响食物通过时间、日摄食量、日粪尿排量、表观消化系数和同化效率。食物通过时间在26 -34℃范围内随体温升高而缩短,在更高的体温下则延长。蜥蜴在30、32、34和36℃体温下明显摄入较多的食物、排出明显较多的粪尿。34℃和36℃下的表观消化系数和同化效率大于其它更低或更高温度下的对应数值,但这两个变量未因体温变化而呈现清晰的规律性变化。疾跑速在18 -36℃范围内随体温升高而加快,在38℃体温下则减缓。36℃或附近体温最适合疾跑速。疾跑速最适体温接近蜥蜴的选择体温,表明蜥蜴疾跑速的最适温度可能与其选择体温密切相关[动物学报52 (2) : 256 -262 , 2006]。     

Upscaling leaf area index in an Arctic landscape through multiscale observations

Monitoring and understanding global change requires a detailed focus on upscaling, the process for extrapolating from the site‐specific scale to the smallest scale resolved in regional or global models or earth observing systems. Leaf area index (LAI) is one of the most sensitive determinants of plant production and can vary by an order of magnitude over short distances. The landscape distribution of LAI is generally determined by remote sensing of surface reflectance (e.g. normalized difference vegetation index, NDVI) but the mismatch in scales between ground and satellite measurements complicates LAI upscaling. Here, we describe a series of measurements to quantify the spatial distribution of LAI in a sub‐Arctic landscape and then describe the upscaling process and its associated errors. Working from a fine‐scale harvest LAI–NDVI relationship, we collected NDVI data over a 500 m × 500 m catchment in the Swedish Arctic, at resolutions from 0.2 to 9.0 m in a nested sampling design. NDVI scaled linearly, so that NDVI at any scale was a simple average of multiple NDVI measurements taken at finer scales. The LAI–NDVI relationship was scale invariant from 1.5 to 9.0 m resolution. Thus, a single exponential LAI–NDVI relationship was valid at all these scales, with similar prediction errors. Vegetation patches were of a scale of ～0.5 m and at measurement scales coarser than this, there was a sharp drop in LAI variance. Landsat NDVI data for the study catchment correlated significantly, but poorly, with ground‐based measurements. A variety of techniques were used to construct LAI maps, including interpolation by inverse distance weighting, ordinary Kriging, External Drift Kriging using Landsat data, and direct estimation from a Landsat NDVI–LAI calibration. All methods produced similar LAI estimates and overall errors. However, Kriging approaches also generated maps of LAI estimation error based on semivariograms. The spatial variability of this Arctic landscape was such that local measurements assimilated by Kriging approaches had a limited spatial influence. Over scales >50 m, interpolation error was of similar magnitude to the error in the Landsat NDVI calibration. The characterisation of LAI spatial error in this study is a key step towards developing spatio‐temporal data assimilation systems for assessing C cycling in terrestrial ecosystems by combining models with field and remotely sensed data.     

Relationship between growth,nitrogen fixation and assimilation in a legume (Medicago sativa L.)

Summary Symbiotic N₂ fixation, NO ₃ ⁻ assimilation and protein accumulation in the shoots were measured simultaneously in alfalfa (Medicago sativa L.) grown in the field or in pots, in order to study how the balance between the two modes of nitrogen nutrition could be influenced by agronomic factors, such as harvest, mineral nitrogen supply and drought stress. During periods of rapid growth, fixation and assimilation may function simultaneously; they are antagonistic at the beginning and at the end of the growth cycle, when the nitrogen requirement of the plant is lower. When nitrogen nutrition does not limit growth, mineral nitrogen supply favours assimilation at the expense of fixation, but does not modify the amount of nitrogen accumulated, which is adjusted to the growth capacity of the plant. After cutting, nitrate assimilation compensated for the decrease in fixation and supplied the plant with the nitrogen required by the regrowth, the proliferation of which determined the fixation recovery. Drought stress decreased N₂ fixation much more than NO ₃ ⁻ assimilation. The latter made growth recovery possible when water supply conditions became normal again. These results suggested the existence of an optimum level of nitrate assimilation, which differed depending on the age of the plants and allowed both maximum growth and fixing activity.     

CO2浓度升高和不同氮源对紫茎泽兰生长及光合特性的影响

大气CO2浓度升高和植物入侵是全世界面临的两大重要问题。CO2浓度升高促进植物的光合作用,但在某些植物中,这种促进作用出现在短期高浓度CO2下,而在长期高浓度CO2处理下消失（称为CO2驯化）,被认为源于高浓度CO2对光呼吸和NO-3同化的抑制。通过比较研究不同形式氮源（全氮、硝态氮）和短期（8 days）、长期（40 days）CO2浓度升高处理对入侵植物紫茎泽兰生理特征的影响,结果表明在全氮供应下,短期和长期CO2浓度升高均促进了紫茎泽兰的光合;氨态氮缺失情况下,长期CO2浓度升高促进紫茎泽兰的光合,而短期CO2浓度升高对紫茎泽兰的光合没有促进作用;缺NH＋4下,短期高浓度CO2提高了叶片叶绿素含量,长期CO2升高又使其回复到正常CO2下的较低水平。这些结果表明紫茎泽兰并不会对长期的CO2升高产生驯化,即长期CO2升高会促进紫茎泽兰的光合作用,而且这一促进作用不受土壤中缺NH＋4的影响。鉴于培养介质中缺NH＋4会导致一些植物产生“CO2驯化”,未来CO2浓度升高情况下,在缺NH＋4的土壤中,紫茎泽兰的竞争力可能会更强。