根际养分状况数学模拟研究的进展

土壤养分有效性的核心问题是土壤中养分离子向根的迁移,而离子向根迁移则是由于植物根吸收水分和养分产生的梯度所引起。     

根际土壤磷的动态

养分的有铲性是由土壤物理、化学和生物学特性，特别是根系主导的根际动态所决定的的，根系引起根际ＰＨ值和Ｅｈ、根分泌物以及由此而引起微生物种群、数量和活性的改变，从根本上决定着根际养分的动态而根系的动态又受植物生长的调控。根际微生态系统直接影响到土壤养分向根系的转移和被根系的吸收利用。因此，研究养分在根系－－土壤微环境中的动态是十分重要的。     

秦岭北坡刺槐人工林细根垂直分布及其与土壤养分的关系

采用土钻法对秦岭北坡刺槐人工林3种细根参数垂直分布状况和土壤化学性质进行系统研究.并在对这两者进行研究的基础上,就土壤养分因子对细根垂直分布的影响进行分析.研究发现,随着土层深度的增加,刺槐林细根参数总体上表现为降低的趋势.多种土壤养分因子在土层中表现出各自不同的变化趋势.细根参数在土层中的垂直分布受到土壤养分因子的重要影响.其中土壤有机质和全氮含量对细根参数在土层中垂直分布的影响最为明显.而在细根生物量,细根表面积,根长密度3种细根参数中.植物对养分的吸收与细根表面积的关系最为密切.     

根际微生物对药材道地性的影响

在植物、土壤与微生物所构成的根际微生态系统中,微生物对于土壤肥力的形成、养分的转化吸收、植物生长发育以及植物病虫害的生物防治具有重要的作用.通过对影响根际微生物种群结构因素分析以及根际微生物影响土壤养分释放和植物生长等功能的初步探讨,以期为药材道地性的研究提供新的思路和方法,指导道地药材的生产和实践.     

施肥对婆婆纳、离子芥、小花糖芥3种麦田杂草根际pH的影响

根际是受根系影响而在物理、化学和生物学性质等方面均不同于土体的极小部分土壤区域.研究表明:植物生长过程中,由于根系的代谢作用而向根外排泄H 或HCO3-,使根际土壤pH发生较大变化.而根际土壤的pH直接影响到土壤养分的活性和生物有效性.故不同植物根际土壤的pH状况可反映出它们对土壤氮、磷、钾养分吸收利用能力的相对大小.     

土壤—根系微区养分状况的研究——Ⅲ.水稻根际氮素的变化

植物根系吸收性能与土壤养分、水分和温度等环境条件有着密切的关系,同时又影响着近根微区土壤中养分的迁移和有效性。近年来在这一方面有了不少进展^[5]。在本项研究的第Ⅱ报^[1]中,我们曾对棉花等旱作根际钾的亏缺与富集及与土壤条件和作物种类的关系进行了初步讨论。但是,根际氮的状况除了从微生物的角度做了一些工作外,对植物根系吸收过程中氮肥的亏缺与补给,以及影响范围的论述还很少。Harmsen和Jager^[6],在旱作根际土壤中曾对氮、碳的含量进行了分析,并与根外土壤作过比较,认为近根区存在富集现象。但是,由于试验是全量分析的结果,因此只能归结为近根土壤中有微生物和某些生物残休的聚集,不能了解有效氮的动向。     

根际养分活化与吸收过程的定量模拟研究进展

在论述植物根系作为养分的主动吸收槽，对根示养分生物有铲性产生重要作用的前提下，本文扼要讨论了根际ＰＨ值变化，根分泌螯合物与 性物及根际微生物在根际土壤养分活化中的作用过程，并重点评述了有关养分活化与吸收模拟模型的进展与发展趋势。     

有机物料对苹果根际营养元素动态及土壤酶活性的影响

有机物料的施用,影响着土壤的理化特性与生物性状,也必然影响植物的生长发育.植物与土壤直接接触区域是根际微域,要了解有机物料对作物生长发育的影响,必须先探讨其对根际微域的作用.研究与揭示根际微域环境状况对增加土壤养分供应,促进根系对养分吸收、改善树体营养状况及提高产量与品质等方面具有重要意义[1].果树根际微域的研究工作开展较少[1,2],为此我们研究了两种有机物料对苹果砧木根际微域中土壤酶活性及元素有效性的影响.     

棉花氮磷营养的根际效应

本文在自行设计、可供全生育期应用的根际培养箱中，成功地进行取地主根系作物棉花根际土壤中速效ＮＰ养分变化及其根际效应研究。结果表明；在新疆特定的自然条件下，棉株对土壤有效Ｎ吸收的影响范围为距根１０ｍｍ左右；对土壤速效Ｐ吸收的影响范围为距根３ｍｍ左右；明显的根际互促效应生产施肥提供了科学依据。     

根表铁膜对元素吸收的效应及其影响因素

水生植物根系表面普遍形成铁膜,铁膜的形成是水生植物适应淹水和其他环境胁迫的重要机制之一.大量研究表明铁膜在植物吸收有益营养元素和有害元素中有重要作用.本文总结了植物根表铁膜形成的过程及铁膜的形态、组分、数量等特征,阐述了铁膜对植物吸收元素的效应.水生植物根表的铁膜能够阻止植物对金属元素的吸收,也可充当植物根系表面的养分"库",在植物需要养分时铁膜中的养分可以被活化并被植物吸收利用.此外铁膜的效应还与根表铁膜的数量有关,少量铁膜能够促进植物对养分的吸收,而大量铁膜则阻止植物对养分的吸收.造成铁膜不同效应的因素包括植物、重金属和研究采用的手段和技术等.如植物种类、品种、生育阶段以及营养状况、植物的培养方式、所研究的金属离子种类以及根表铁膜的分析技术等均可影响试验结果.进一步的研究工作需考虑铁膜形成的外部环境,利用原位技术以确定铁膜中元素的分布和化学形态,并将铁膜的效应与土壤植物的整体反应结合起来进行系统的研究.     

大豆品种耐低磷和对磷肥效应的遗传差异

大豆不同品种对低磷胁迫和磷肥效应有显著的遗传差异。低磷胁迫下,苗期植株叶片酸性磷酸酶活性（APA）和叶面积与品种的子粒产量呈极显著相关;APA、叶面积、干物质量和氮积累量与生物学产量呈显著或极显著相关。但在施磷条件下,它们之间则无相关关系。这表明APA、叶面积、干物质量和氨积累量可作为耐低磷基因型的筛选指标。试验表明,耐低磷能力弱的品种对磷肥反应更为敏感。在低磷和施磷条件下产量均较高的品种也是存在的,它们对不同的磷素营养环境有着广泛的适应性,进一步挖掘这类基因型很有意义。     

广东大豆地方种质磷效率特性研究Ⅰ.大豆基因型磷效率特性差异及其与土壤有效磷含量的关系

在低磷红壤上,对原产广东省的大豆(Glycine max (L.) Merrill)基因型磷效率与其来源地土壤有效磷含量的关系进行研究.结果表明:植株磷素吸收量相对值(RVPPU)不仅可以反映大豆对低磷红壤生长适应性,而且可以反映大豆基因型磷效率特性,RVPPU是衡量田间生长适应性和磷效率特性的较好指标.RVPPU较大的大豆基因型,其对低有效磷红壤环境适应性较好,磷效率特性较佳;反之,亦然.不同大豆基因型,具有不同的磷效率特性.磷效率特性的形成与土壤有效磷含量有关.土壤中低有效磷含量与较佳的磷效率特性形成有关,长期生长在有效磷含量较低的砖红壤、赤红壤、红壤和紫色土上的大豆基因型具有较佳的磷效率特性;而长期生长在有效磷含量较高的水稻土、潮土上的大豆基因型其磷效率特性较差.大豆基因型较佳的磷效率特性是其长期在低有效磷土壤环境下进化形成的.     

水稻土的标准需磷量对水稻籽粒产量及吸磷量的影响

就水稻土的标准需 P 量对水稻籽粒产量及吸 P 量的影响进行了探讨,目的在于确定供试水稻土的“P 临界平衡浓度”,为指导广东省水稻土的合理施用 P 肥提供参考。供试土壤分别是广东省玄武岩母质发育的水稻土(1 号土)和珠江三角洲沉积物母质发育的水稻土(2 号土)。结果表明:两种供试水稻土对标准需 P量的产量参数反应有显著差异。建议将 P 0.15 mg/kg 定为广东省玄武岩母质发育的水稻土(1 号土)的 “P 临界平衡浓度”,这样可以使 1 号土的水稻产量达到最高产量的 95 %以上。关于能否用 P 0.15 mg/kg 作为珠江三角洲沉积物母质发育的水稻土和其他母质发育水稻土的“P 临界平衡浓度”,有待于进一步研究。     

土壤对磷的吸附与解吸及需磷量探讨

本文探讨了不同质地土壤对磷的吸附与解吸。根据Langmuir方程式求出不同土壤对磷的最大吸附量。影响磷吸附的土壤理化性质主要为粘粒含量、碳酸盐含量和有效磷含量。以Freundhich方程式X=ac^b中的c值为每克土中含P0.2μg时而计算出的X量可做为施磷量的依据。     

GENOTYPIC DIFFERENCES IN PHOSPHORUS UPTAKE AND UTILIZATION OF WATERMELON UNDER LOW PHOSPHORUS STRESS

In this study, seven watermelon (Citrullus lanatus) cultivars were tested in solution culture experiment with limiting and ample phosphorus (P) supply to evaluate P uptake and utilization of watermelon under low P stress. Different genotypes showed considerable diversity in terms of biomass accumulation, P uptake, P utilization, root morphological parameters and photosynthetic parameters under low P stress. At low P supply, genotype XN8 and ZCHY were clearly superior to other genotypes in terms of total dry matter yield. The genotype ZJ has the highest P uptake ability, while the genotype XN8 has the highest P efficiency ratio and P utilization efficiency among the seven genotypes under low P stress. The P uptake ability of these genotypes was related significantly and positively to root morphological parameters and photosynthesis parameters under low P stress, the P utilization efficiency showed significant and positive correlation with total dry matter. Results showed existence of genetic differences among watermelon genotypes with regard to P absorption and utilization. The seven genotypes were classified into four groups: efficient responsive (ER), inefficient responsive (IER), efficient non-responsive (ENR) and inefficient nonresponsive (IENR) according to P utilization efficiency under low P stress and dry matter at high P supply. XN8 was identified as ER, and ZCHY was identified as ENR, which may be valuable resources for watermelon production in different soil with low P stress.     

INTERACTION OF MOLYBDENUM AND PHOSPHORUS SUPPLY ON UPTAKE AND TRANSLOCATION OF PHOSPHORUS AND MOLYBDENUM BY BRASSICA NAPUS

A hydroponic trial was conducted to assess interaction of molybdenum (Mo) and phosphorus (P) on uptake and translocation of P and Mo by Brassica napus. Molybdenum was applied at four rates (0, 0.01, 0.1 and 1 mg L^?1) and P at three rates (1, 30, and 90 mg L^?1) in nutrient solution. The results indicated that P increased shoot growth and 0.01 mg L^?1 Mo improved the growth of shoots and roots. Molybdenum increased shoot P uptake and root P concentration and uptake when higher P was provided, and had a stimulating effect on P translocation from shoots to roots. P increased shoot Mo concentration and uptake, decreased those in roots, and enhanced Mo transport from roots to shoots. These results implied that both Mo and P had beneficial effects on Mo and P absorption and translocation and co-application of them were necessary to promote growth and utilization of Mo and P for Brassica napus.     

土壤有效磷的测定方法及其与磷素形态关系的研究

土壤有效磷的化学速测法,目前仍是了解土壤磷素肥力水平的主要手段之一。     

EXPLOITATION OF PHOSPHORUS PATCHES WITH DIFFERENT PHOSPHORUS ENRICHMENT BY THREE ARBUSCULAR MYCORRHIZAL FUNGI

The effect of three arbuscular mycorrhizal (AM) fungi on phosphorus (P) nutrient activation and acquisition by maize from spatially heterogeneous sand was investigated using dual-mesh packages enriched with different P concentrations and compared with non-mycorrhizal cotrols. As would be expected the AM fungi significantly enhanced leaf photosynthetic rate and the biomass and P concentrations in shoots and roots. All three fungi (Glomus intraradices, Glomus mosseae and Glomus etunicatum) displayed the capacity to dissolve inorganic P and promoted P nutrient availability in the packages (P patches). G. etunicatum showed the largest effect comparing with Glomus intraradices and Glomus mosseae, particularly in packages with high concentrations of P. Possible mechanisms involved include the acidification of the P patches by the AM fungi, promotion of the dissolution of the P, and more marked effects of the three fungal isolates with increasing enrichment of P in the patches. Inoculation with G. etunicatum resulted in greater acidification compared to the other two fungi. We conclude that AM fungi can promote P availability by acidifying the soil and consequently exploiting the P in nutrient patches and by facilitating the growth and development of the host plants.     

EFFECT OF PHOSPHORUS APPLICATION ON HIERARCHICAL LATERAL ROOT MORPHOLOGY AND PHOSPHORUS ACQUISITION IN SOYBEAN

Root growth systems are hierarchical and sensitive to nutrient availability in soil. Lateral roots are an important component of plant root morphology. Phosphorus (P) availability regulates root branching in plants such as Arabidopsis thaliana, barley (Hordeum vulgare), and rice (Oryza sativa L.). However, little information is available for soybean (Glycine max L.). A pot experiment was conducted to determine the morphological characteristics of lateral roots of different orders and P acquirement of soybean seedlings under three levels of applied P of 0, 50 and 100 mg P kg^?1 soil. Root length, an important parameter of root characteristics, differed in four orders. Lateral roots in the second and third order contributed 39.4 and 34.2% of total root length, respectively. Moreover, since most of lateral roots were fine roots (roots having a diameter 0.5 mm), fine roots had a frequency distribution of 58.5 to 61.4% in the second and third orders. Phosphorus application significantly increased dry weight, total length and number of lateral roots in the four orders with the ranking of fourth > third > second > first (P ≤ 0.05), but did not affect the average length of a lateral root. Phosphorus application reduced the frequency distribution of fine lateral roots in the first and second orders, while increased in the third and fourth orders (P ≤ 0.05). Compared with the medium P application (50 mg P kg^?1 soil), the high P application (100 mg P kg^?1 soil) inhibited lateral root growth with decreases in root dry weight, root length and root number at all orders. Phosphorus concentration and content increased with the increase in P application. The correlation between characteristics of lateral root and P status in the plants varied among root orders. The length of lateral roots from first to third order had a positive correlation with P concentration in root and shoot, and had a good relationship with P content. Lateral root numbers at the second, third and fourth orders were significantly correlated with P content while no correlation was found with the average length of a lateral root. It is proposed that the main effect of P application appears to be on the lateral root initiation rather than on lateral root elongation, and P favors the lateral root formation of the higher orders. The total length and number of lateral root at the second and third orders play a more important role in P content than those at other lateral root orders.     

植物高效利用土壤磷营养的化学机理

本文闸述了植物根系分泌物与土壤磷素有效性的相互关系。根据根系分泌物的化学特性,从七个方而讨论了植物活化土壤磷素的机理。