异质低磷胁迫下马尾松家系根构型和磷效率的遗传变异

以7个马尾松(Pinus massoniana)一代种子园自由授粉家系为材料, 设置同质低磷(P)胁迫和异质低P胁迫模拟的盆栽试验, 系统研究马尾松家系对不同类型低P胁迫的适应机制和P效率变异规律。结果表明, 参试马尾松家系的苗高、地径和生物量等P效率指标均表现出显著的家系变异, 主要P效率指标的家系遗传力均较高, 干物质积累量的广义遗传力大于0.80, 揭示了马尾松P营养效率的较大遗传改良潜力。马尾松对不同类型低P胁迫的适应机制有所差异。在同质低P胁迫下, ‘3201’、‘1217’等高P效率家系的根系主要参数均高于低P效率家系, 表明整体根系参数的适应性变化是P效率和生物量形成的决定因素。在异质低P胁迫下, 高P效率马尾松家系在表层富P介质的根系分布量、分布比例均显著增加, 表层根系参数与马尾松家系P效率呈显著正相关, 揭示根系空间构型的适应性变化是决定马尾松高P效率的重要生物学基础。表层根系生物量、表层根相对比例的家系遗传力达0.88和0.72, 证实了以马尾松根构型的适应变化为突破口, 选育具有理想根构型和较高P效率的马尾松家系。     

Endophyte roles in nutrient acquisition,root system architecture development and oxidative stress tolerance

Plants associate with communities of microbes (bacteria and fungi) that play critical roles in plant development, nutrient acquisition and oxidative stress tolerance. The major share of plant microbiota is endophytes which inhabit plant tissues and help them in various capacities. In this article, we have reviewed what is presently known with regard to how endophytic microbes interact with plants to modulate root development, branching, root hair formation and their implications in overall plant development. Endophytic microbes link the interactions of plants, rhizospheric microbes and soil to promote nutrient solubilization and further vectoring these nutrients to the plant roots making the soil-plant-microbe continuum. Further, plant roots internalize microbes and oxidatively extract nutrients from microbes in the rhizophagy cycle. The oxidative interactions between endophytes and plants result in the acquisition of nutrients by plants and are also instrumental in oxidative stress tolerance of plants. It is evident that plants actively cultivate microbes internally, on surfaces and in soils to acquire nutrients, modulate development and improve health. Understanding this continuum could be of greater significance in connecting endophytes with the hidden half of the plant that can also be harnessed in applied terms to enhance nutrient acquisition through the development of favourable root system architecture for sustainable production under stress conditions.     

植物根系养分捕获塑性与根竞争

为了更有效地从土壤中获取养分, 植物根系在长期的进化与适应中产生了一系列塑性反应, 以响应自然界中广泛存在的时空异质性。同时, 植物根系的养分吸收也要面对来自种内和种间的竞争。多种因素都会影响植物根竞争的结果, 包括养分条件、养分异质性的程度、根系塑性的表达等。竞争会改变植物根系的塑性反应, 比如影响植物根系的空间分布; 植物根系塑性程度差异也会影响竞争。已有研究发现根系具有高形态塑性和高生理塑性的植物在长期竞争过程中会占据优势。由于不同物种根系塑性的差异, 固定的对待竞争的反应模式在植物根系中可能并不存在, 其响应随竞争物种以及土壤环境因素的变化而变化。此外, 随着时间变化, 根系塑性的反应及其重要性也会随之改变。植物对竞争的反应可能与竞争个体之间的亲缘关系有关, 有研究表明亲缘关系近的植物可能倾向于减小彼此之间的竞争。根竞争对植物的生存非常重要, 但目前还没有研究综合考虑植物的各种塑性在根竞争中的作用。另外根竞争对群落结构的影响尚待深入的研究。     

3D reconstruction and dynamic modeling of root architecture in situ and its application to crop phosphorus research

Root architecture plays important roles in plant water and nutrient acquisition. However, accurate modeling of the root system that provides a realistic representation of roots in the soil is limited by a lack of appropriate tools for the non‐destructive and precise measurement of the root system architecture in situ. Here we describe a root growth system in which the roots grow in a solid gel matrix that was used to reconstruct 3D root architecture in situ and dynamically simulate its changes under various nutrient conditions with a high degree of precision. A 3D laser scanner combined with a transparent gel‐based growth system was used to capture 3D images of roots. The root system skeleton was extracted using a skeleton extraction method based on the Hough transformation, and mesh modeling using Ball‐B spline was employed. We successfully used this system to reconstruct rice and soybean root architectures and determine their changes under various phosphorus (P) supply conditions. Our results showed that the 3D root architecture parameters that were dynamically calculated based on the skeletonization and simulation of root systems were significantly correlated with the biomass and P content of rice and soybean based on both the simulation system and previous reports. Therefore, this approach provides a novel technique for the study of crop root growth and its adaptive changes to various environmental conditions.     

低磷胁迫下不同种源马尾松的根构型与磷效率

以浙江淳安、福建武平、广西岑溪和广东信宜4个代表性的马尾松种源为试材,设置异质低磷胁迫、同质低磷胁迫等不同磷素处理,研究马尾松种源感知不同类型低磷胁迫的根构型及磷效率变异规律.结果表明:无论在异质低磷还是同质低磷胁迫下,参试种源马尾松的主要生长性状和磷效率指标均存在极显著的种源间变异.异质低磷胁迫下,广东信宜、福建武平种源马尾松表现出较高的磷效率和干物质积累量,根构型发生适应性变化,富磷表层介质中的根系参数显著高于低磷效率的广西岑溪和浙江淳安种源.这是磷高效种源具有较高的磷素吸收效率和磷效率的重要机制.不同种源的表层富磷介质根系参数与其整株干物质积累量相关系数在0.95以上.同质低磷胁迫下,高磷效率种源马尾松的磷吸收率显著高于低磷效率种源,但表层介质中的根系参数和整株根系参数与整株干物质积累量的相关性较低.不同种源马尾松适应同质低磷胁迫和异质低磷胁迫的生物学机制有所差异,应有针对性地选择不同土壤磷素的森林立地并推广磷营养高效的马尾松种源.     

Evolving technologies for growing,imaging and analyzing 3D root system architecture of crop plants

A plant's ability to maintain or improve its yield under limiting conditions,such as nutrient de ficiency or drought,can be strongly in fluenced by root system architecture(RSA),the three-dimensional distribution of the different root types in the soil. The ability to image,track and quantify these root system attributes in a dynamic fashion is a useful tool in assessing desirable genetic and physiological root traits. Recent advances in imaging technology and phenotyping software have resulted in substantive progress in describing and quantifying RSA. We have designed a hydroponic growth system which retains the three-dimensional RSA of the plant root system,while allowing for aeration,solution replenishment and the imposition of nutrient treatments,as well as high-quality imaging of the root system. The simplicity and flexibility of the system allows for modi fications tailored to the RSA of different crop species and improved throughput. This paper details the recent improvements and innovations in our root growth and imaging system which allows for greater image sensitivity(detection of fine roots and other root details),higher ef ficiency,and a broad array of growing conditions for plants that more closely mimic those found under field conditions.     

Opportunities to improve nutrient efficiency in pigs and poultry through breeding

Efficiency of food and nutrient (including energy) use are considered the key factors in the economic and environmental performance of livestock systems. The aim of this paper is to consider the basis of genetic variation in the components that constitute dietary nutrient efficiency; and to conclude whether there would be benefit, in any relevant terms, in including these components in breeding programmes that aim to improve nutrient efficiency within pig and poultry systems of production. The components considered are (i) external, pre-ingestion losses, such as food spillage and its relation to feeding behaviour traits, (ii) digestive efficiency, (iii) maintenance requirements, (iv) net efficiency of energy and nutrient utilisation and (v) partitioning of scarce resources within productive and between productive and fitness functions. It is concluded that opportunities to exploit genetic variation exist mainly in the potential to improve the digestive efficiency of pigs and to reduce the maintenance requirements for resources mainly in hens, but also potentially in pigs. Current evidence suggests that there are very weak genetic and phenotypic correlations between components of feeding behaviour and productive traits, and little genetic variation in the net efficiency of nutrient utilisation among poultry and pig genotypes. The implication of the latter is that there would be little exploitable genetic variation in the partitioning of scarce nutrients between productive functions. Currently, there is a lack of understanding of the genetic basis of the partitioning of scarce nutrients between productive and fitness functions, and how this may impact upon the efficiency of nutrient use in pig and poultry systems. This is an area of research to which further effort might usefully be devoted.     

Plant nutrient efficiency: A comparison of definitions and suggested improvement

Selection of plant cultivars tolerant of low nutrient supply may increase productivity on low fertility soils and reduce fertilizer requirements. Considerable effort has been directed towards identifying nutrient efficient species and germplasms, but the many different definitions for efficiency make the use of the term ambiguous. The concept of nutrient efficiency was evaluated using data from a study of differences in germplasm response to phosphorus (P) availability in white clover (Trifolium repens L.) and alfalfa (Medicago sativa L.) grown in a sand-alumina culture. Application of various criteria identified in the literature as measures of nutrient efficiency did not clarify differences between purportedly P efficient and inefficient germplasms. Germplasms differed in maximum shoot and total dry mass and in solution P concentration required to achieve 80% maximum yield, but not in tissue P concentration, internal P utilization, or P uptake per unit of fine root dry mass. Differences may have resulted from factors other than efficient use of available P. To reduce the confounding effects that other factors have on nutrient efficiency, we propose that equivalent yields of germplasms be demonstrated where nutrients are not limiting. Mechanisms that enable enhanced nutrient efficiency can be identified less ambiguously using this improved approach.Joint contribution of the Minnesota Agricultural Experimental Station, USDA-ARS and US Dairy Forage Research Center (Minnesota cluster). Paper No. 20,432 of the Minnesota Science Journal Series.Joint contribution of the Minnesota Agricultural Experimental Station, USDA-ARS and US Dairy Forage Research Center (Minnesota cluster). Paper No. 20,432 of the Minnesota Science Journal Series.     

Study of differences between vertical root maps observed in a maize crop and simulated maps obtained using a model for the three-dimensional architecture of the root system

Differences between observed and simulated vertical root maps were studied in an attempt to evaluate the predictive ability of a simulation model of root system architecture under field conditions on mature plants, and to identify avenues for improvement. Some methodological problems associated with root mapping in the field are considered with a sensitivity analysis.Comparisons were made on a maize crop (early maturing hybrid F1 cultivar Dea) 15 days after silking. Four vertical root maps, perpendicular to the row and midway between two successive plants, were observed. Simulated root maps for different locations along the row showed essentially the same pattern, attesting of an approximately two-dimensional distribution of the roots in such a crop. Simulation of the intesection of roots with thin layers (thickness from 0 to 20 mm) instead of a perfect plane allowed us to assess effects due to the roughness of actual trench walls, and possible artefacts in the observation of root intersections. The simulated root profiles were very sensitive to this thickness, especially in the 0–5 mm range, in both average values, and overall shape. Actual data were close to the 3 mm thick simulations. This value seems plausible under our field conditions.Differences between simulated and actual root maps were shown to be mostly accounted for by the variations in soil bulk density. Thus, this environmental parameter appears as the most important one to include into the model for improving its predictions.     

Osmotic regulation of root system architecture

Although root system architecture is known to be highly plastic and strongly affected by environmental conditions, we have little understanding of the underlying mechanisms controlling root system development. Here we demonstrate that the formation of a lateral root from a lateral root primordium is repressed as water availability is reduced. This osmotic-responsive regulatory mechanism requires abscisic acid (ABA) and a newly identified gene, LRD2. Mutant analysis also revealed interactions of ABA and LRD2 with auxin signaling. Surprisingly, further examination revealed that both ABA and LRD2 control root system architecture even in the absence of osmotic stress. This suggests that the same molecules that mediate responses to environmental cues can also be regulators of intrinsic developmental programs in the root system.     

Breeding crop plants with deep roots: their role in sustainable carbon, nutrient and water sequestration

BACKGROUND: The soil represents a reservoir that contains at least twice as much carbon as does the atmosphere, yet (apart from 'root crops') mainly just the above-ground plant biomass is harvested in agriculture, and plant photosynthesis represents the effective origin of the overwhelming bulk of soil carbon. However, present estimates of the carbon sequestration potential of soils are based more on what is happening now than what might be changed by active agricultural intervention, and tend to concentrate only on the first metre of soil depth. SCOPE: Breeding crop plants with deeper and bushy root ecosystems could simultaneously improve both the soil structure and its steady-state carbon, water and nutrient retention, as well as sustainable plant yields. The carbon that can be sequestered in the steady state by increasing the rooting depths of crop plants and grasses from, say, 1 m to 2 m depends significantly on its lifetime(s) in different molecular forms in the soil, but calculations (http://dbkgroup.org/carbonsequestration/rootsystem.html) suggest that this breeding strategy could have a hugely beneficial effect in stabilizing atmospheric CO(2). This sets an important research agenda, and the breeding of plants with improved and deep rooting habits and architectures is a goal well worth pursuing.     

稻茬麦根系构型的定向分型分析

为探索稻茬麦根构型的方向性,使用田间数字化仪实现稻茬麦根系的数值化,将根系数据导入Pro-E重构出根系的空间状态图,然后将根构型每隔10°进行各向投影,计算根系构型在18个维度的分形维数与分形丰度.结果表明:小麦苗期根构型在各维度的分形特征具有较强的规律性,表明根系在土体中的分布具有明显的方向性.在苗期到返青期,根构型在18个维度的分形指标波动性大,表明这一时期内根系生长处于持续的动态变化过程.在拔节期,根构型在各维度的分形再次呈现出一定的规律性,表明根系在土体中的分布重新表现出明显的方向性.该研究方法可以精准描述和分析植物根系在田间环境中的分布状况.     

Functional aspects of root architecture and mycorrhizal inoculation with respect to nutrient uptake capacity

The aim of this research was to investigate the effect of arbuscular mycorrhizal (AM) colonisation on root morphology and nitrogen uptake capacity of carob ( Ceratonia siliqua L.) under high and low nutrient conditions. The experimental design was a factorial arrangement of presence/absence of mycorrhizal fungus inoculation ( Glomus intraradices) and high/low nutrient status. Percent AM colonisation, nitrate and ammonium uptake capacity, and nitrogen and phosphorus contents were determined in 3-month-old seedlings. Grayscale and colour images were used to study root morphology and topology, and to assess the relation between root pigmentation and physiological activities. AM colonisation lead to a higher allocation of biomass to white and yellow parts of the root. Inorganic nitrogen uptake capacity per unit root length and nitrogen content were greatest in AM colonised plants grown under low nutrient conditions. A better match was found between plant nitrogen content and biomass accumulation, than between plant phosphorus content and biomass accumulation. It is suggested that the increase in nutrient uptake capacity of AM colonised roots is dependent both on changes in root morphology and physiological uptake potential. This study contributes to an understanding of the role of AM fungi and root morphology in plant nutrient uptake and shows that AM colonisation improves the nitrogen nutrition of plants, mainly when growing at low levels of nutrients.     

供磷水平及方式对杉木幼苗根系生长和磷利用效率的影响

为研究杉木幼苗根系生长、形态学指标及养分利用效率对土壤磷素异质分布的响应规律,选择杉木种子园单株采种培育的半同胞家系实生幼苗为研究对象,采用室内沙培控磷盆栽试验,设计低浓度供磷(8 mg/kg KH₂PO₄)、正常供磷(16 mg/kg KH₂PO₄)和高浓度供磷(32 mg/kg KH₂PO₄)3个供磷水平,每个供磷水平分别采用2种供磷方式(局部供磷和均匀供磷)进行根部施磷。结果表明:(1)从供磷水平来看,低浓度供磷下的杉木根长、根系生物量、根冠比、根系及全株的磷素利用效率均显著大于正常供磷和高浓度供磷,而根平均直径相反;随着供磷水平的提高,杉木苗高和地上部生物量无显著差异,而比根长表现出逐渐降低的趋势。(2)从供磷方式来看,局部供磷处理的杉木苗高、根长、根系表面积、比根长、地上部生物量、根系及全株的磷素利用效率均显著大于均匀供磷处理,而根平均直径和根冠比则相反。总体上,低浓度局部供磷处理下杉木可明显增强其根系的形态可塑性,从而优化根系在养分异质土壤里的...