不同土壤水分条件下施磷量对小麦旗叶衰老及产量的影响

在防雨旱棚池栽条件下研究了水分胁迫(W1)和水分适宜(W2)条件下不同施磷量对小麦旗叶衰老及产量的影响.结果表明,小麦开花后,W1水平下,施磷150 kg/hm~2处理的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)下降幅度及丙二醛(MDA)上升幅度较其他处理小;W2水平下,随施磷量的增加,SOD、POD和CAT活性增加、MDA降低,可见水分胁迫下适宜的施磷量以及适宜的水分条件下增加施磷量均可以改善小麦体内的保护酶,增加小麦叶面积指数和旗叶叶绿素含量,提高光合速率,进而延缓衰老,提高产量.本试验条件下,虽然75%土壤田间持水量与施磷量150 kg/hm~2的处理组合达到了最高产量,但与55%土壤田间持水量与施磷量150 kg/hm~2的处理组合的产量差异不显著,综合观之,后者是最佳水肥处理组合.     

Spatial variation of soil test phosphorus in a long‐term grazed experimental grassland field

The spatial variation of soil test P (STP) in grassland soils is becoming important because of the use of STP as a basis for policies such as the recently EU‐introduced Nitrate Directive. This research investigates the spatial variation of soil P in grazed grassland plots with a long‐term (38 y) experiment. A total of 326 soil samples (including 14 samples from an adjacent grass‐wood buffer zone) were collected based on a 10 × 10 m² grid system. The samples were measured for STP and other nutrients. The results were analyzed using conventional statistics, geostatistics, and a geographic information system (GIS). Soil test P concentrations followed a lognormal distribution, with a median of 5.30 mg L^–1 and a geometric mean of 5.35 mg L^–1. Statistically significant (p < 0.01) positive correlation between STP and pH was found. Spatial clusters and spatial outliers were detected using the local Moran's I index (a local indicator of spatial association) and were mapped using GIS. An obvious low‐value spatial‐cluster area was observed on the plots that received zero‐P fertilizer application from 1968 to 1998 and a large high‐value spatial‐cluster area was found on the relatively high‐P fertilizer application plots (15 kg ha^–1 y^–1). The local Moran's I index was also effective in detecting spatial outliers, especially at locations close to spatial‐cluster areas. To obtain a reliable and stable spatial structure, semivariogram of soil‐P data was produced after elimination of spatial outliers. A spherical model with a nugget effect was chosen to fit the experimental semivariogram. The spatial‐distribution map of soil P was produced using the kriging interpolation method. The interpolated distribution map was dominated by medium STP values, ranging from 3 mg to 8 mg L^–1. An evidently low‐P‐value area was present in the upper side of the study area, as zero or short‐term P fertilizer was applied on the plots. Meanwhile, high‐P‐value area was located mainly on the plots receiving 15 kg P ha^–1 y^–1 (for 38 y) as these plots accumulated excess P after a long‐term P‐fertilizer spreading. The high‐ or low‐value patterns were in line with the spatial clusters. Geostatistics, combined with GIS and the local spatial autocorrelation index, provides a useful tool for analyzing the spatial variation in soil nutrients.     

Effect of air‐drying on phosphorus fractions in clay soil

Despite the publication of a number of papers dealing with the effect of drying on the soil labile P pool, less attention has been paid to the possible drying‐evoked changes in the more stable P pools. We applied Hedley's sequential fractionation procedure that aims at quantifying soil P reserves according to their decreasing plant availability to examine the effects of drying on soil P fractions in clayey soil samples of different cultivation history. To further investigate the contribution of organic matter disruption to the solubility of soil P, the P extracted in each fractionation step was divided into two size classes by filtering the suspension through a 0.2 μm membrane filter. There were no air‐drying‐induced changes in the total amount of P extracted in each fractionation step. However, air‐drying changed the distribution of water‐extractable P in size fractions; increase in the small‐sized P took place at the expense of large‐sized P. Air‐drying increased also small‐sized molybdate‐unreactive P (MUP) in the NaOH fraction giving evidence that drying‐induced alterations take place also in less labile P forms. The results revealed that air‐drying alters the extractability and distribution of P in various pools rather than the total amount of extracted P and that a large proportion of H₂O‐ and NaOH‐extractable large‐sized MUP may remain undetected if only filtered samples are analyzed.     

低磷胁迫对不同基因型甜菜抗性生理特征的效应

选用对低磷胁迫抗性各异的3个甜菜品种:品20、品17和品14,在人工培养室内采用沙培试验法,研究了甜菜抗耐低磷胁迫的生理机制。结果表明,低磷胁迫限制了甜菜对磷的吸收,导致植株含磷量和生物产量显著下降;不同品种间差异显著,品14降幅最大,品17次之,品20最小。与足磷处理(P 100μmol/L)相比,低磷胁迫后甜菜品种间体内抗性生理特征差异显著。其中,品14和品17的丙二醛含量、脯氨酸含量、过氧化物酶活性均显著增加;品20的丙二醛含量、脯氨酸含量极显著下降,而过氧化物酶活性变化不显著。叶片中Mg2+-ATPase活性降低,不同品种降幅各异,从小到大依次为品20品17品14,其中品20与后两者间的差异均达显著。品20和品17体内的钙调素(CaM)含量显著增加,而品14变化不明显,其相对值从大到小依次为品20品17品14,差异显著,与品种自身抗磷胁迫能力顺序一致。不同磷素营养条件对甜菜抵御外界不良环境有较大影响,叶片在受到热伤害时,抗磷胁迫能力较弱的品14和品17在低磷胁迫时质膜损伤率显著增加;而抗磷胁迫能力较强的品20叶片质膜的损伤率显著下降,抗热能力得到改善。     

湖南稻田土壤有机磷组分的施磷效应、季节变化及生物有效性研究

为探明施用磷肥对湖南稻田土壤有机磷组分的影响、有机磷组分的季节变化及其有效性,以湖南省5种不同母质发育的稻田土壤为供试土壤,通过盆栽试验,研究了稻田土壤有机磷组分的施磷效应、在植稻期间的动态变化及其生物有效性。结果表明,施用磷肥可以使土壤中活性有机磷得到较大的增加,而对活性有机磷、中稳性有机磷和高稳性有机磷影响较小。在施磷和不施磷条件下,土壤有机磷的变化主要是中活性有机磷,而其余3种形态有机磷在水稻生长期间几乎保持不变。不管土壤是否施用磷肥,土壤有效磷与有机磷总量总是呈极显著相关,说明土壤有机磷的确是植物可以利用的有效磷源;在早稻生长期间土壤各形态有机磷的生物有效性的大小顺序为:中活性有机磷中稳性有机磷高稳性有机磷活性有机磷;在晚稻生长期间土壤各形态有机磷的生物有效性一般随水稻生育期不同而不同。     

早籼稻品种遗传改良进程中群体质量的演变特征

以1934～2006年育成,在我国南方广泛种植的16个代表性早籼稻品种为材料,参照生产实践及品种演变阶段,按育成时间将供试品种划分为高秆品种、矮秆品种、矮抗品种、优超品种4种类型,采用常规栽培方法研究其群体质量的演变特征。结果表明,早籼稻品种改良进程中,花后群体光合生产能力增强,干物质积累增加,齐穗期总颖花量增加,高效叶面积率与颖花根流量略有下降,有效叶面积率与成穗率变化不大,单茎茎鞘重呈先下降后略有上升的趋势。早籼稻群体进一步改良的有效途径是增强根系活力,促进根系水分与矿物质的吸收及根系物质向籽粒的转运;提高高效叶面积率,增加花后光合产物积累和总颖花量,进而提高粒叶比,达到源库协调。     

环草石斛野生植株与组培苗总生物碱和多糖含量的比较

对贵州产野生环草石斛植株和组培苗中有效成分(总生物碱和多糖)的含量进行了测定和比较分析。结果表明:不同来源的环草石斛中总生物碱含量顺序为:组培苗>野生样品>市售样品;多糖的含量顺序为:野生样品≥组培苗>市售样品。环草石斛组培苗具备直接提取原药成分的可能性。该研究结果为环草石斛次生代谢产物的工业化生产开辟了新途径并提供了基础数据。     

A comparison of the effect of organic acids and dicalcium phosphate supplementation on phosphorus bioavailability,growth performance and digestive enzyme activities of Labeo rohita fingerlings

The effect of organic acids (OA) and dicalcium phosphate (P_i) supplementation in the feed of Labeo rohita fingerlings was studied by formulating seven practical diets, designed as D1 with no feed additives {dicalcium phosphorus (P_i) and organic acid (OA) blend} while, D2, D3, D4 and D5 were supplemented with P_i at the graded levels of 5, 10, 15 and 20 g/kg, respectively, whereas D6 and D7 contained blend of OA at 15 and 30 g/kg, respectively. The diet supplemented with OA blend exhibited increase (p < .05) in growth of L. rohita fingerlings compared with the diet supplemented with P_i. The OA supplementation at both levels showed significant improvement in nutrients digestibility and minerals absorption in fingerlings. Moreover, in case of muscle proximate composition, crude fat (CF) and crude protein (CP) were increased (p < .05) with the inclusion of OA blend in the diet while crude ash (CA) was improved by P_i supplementation. Additionally, digestive enzyme activities were not affected (p ? .05) by OA blend supplementation while increased activities were observed in the fingerlings fed with P_i diet. Consequently, supplementation of OA blend in the diet improved the growth performance and nutrient status while P_i enhanced digestive enzyme activities of L. rohita fingerlings.     

中国大豆磷素营养及磷高效品种筛选最新进展

磷是影响植物新陈代谢和生长发育的重要元素,但由于其极易被土壤固定,因而有效性非常低.缺磷已成为限制当前农作物产量提高和品质改良主要因素之一,传统农业生产一般通过施肥和土壤改良来提高植物对磷素的利用率.近年来,有学者提出通过发掘和利用磷高效品种来解决植物需磷和土壤供磷矛盾的新途径.文章综述了中国土壤磷素营养及其遗传改良的...     

大叶蟹甲草不同萃取部位抗氧化活性研究

目的研究大叶蟹甲草不同萃取部位的抗氧化活性。方法采用ABTS、DPPH自由基及还原性反应体系,利用分光光度法测定大叶蟹甲草的总提液、乙酸乙酯层、正丁醇层和石油醚层在不同浓度下的抗氧化能力及其总酚含量。结果大叶蟹甲草的不同萃取部位对AB＇IS、DPPH自由基均具有较强的清除能力及还原能力,其结果与浓度呈良好的量效关系。其中乙酸乙酯层抗氧化能力最强,在浓度为0．62mg／mL时,对ABTS自由基的最大清除率为91．57％,对DPPH·的最大清除率为94．87％,与同浓度VC的清除率接近,且其IC50分别为0．066mg／mL、0．004mg／mL,测得乙酸乙酯层总酚含量最高,达10．45％。大叶蟹甲草具有较好的抗氧化能力,其中乙酸乙酯层抗氧化能力最显著,与总酚含量有较大的相关性,同时该结果也客观地反映了DPPH法、ABTS-＋法及还原性法测定大叶蟹甲草抗氧化活性的准确性。