Trait complementarity between fine roots of Stipa purpurea and their associated arbuscular mycorrhizal fungi along a precipitation gradient in Tibetan alpine steppe

Development of fine roots and formation of symbiosis with arbuscular mycorrhizal(AM) fungi represent two strategies for plants to acquire nutrient and water from soil. Here, we elucidated how fine root development and symbolized mycorrhizal fungi with Stipa purpurea responded to the precipitation change in Tibetan alpine steppe ecosystem across a precipitation gradient from 50 mm to 400 mm. As precipitation increased, the proportion of thinner fine roots(diameter < 0.4 mm) in total roots increased significantly; while the mycorrhizal colonization percentage, either associated with thinner or thicker roots, decreased. This phenomenon indicated that fine root development and symbolized mycorrhizal fungi are likely alternative, and plant preferred to develop fine root rather than build a symbiotic relationship with mycorrhizal fungi in more benign niches with higher precipitation. Also, root diameter was negatively correlated with specific root length(SRL), but positively correlated with AM fungal colonization percentage, indicating thicker-root species rely more on mycorrhizal fungi in alpine steppe. The complementarity between fine root and mycorrhizal fungi of S. purpurea is mediated by precipitation in Tibetan alpine steppe.

Cell Production and Expansion in the Primary Root of Maize in Response to Low-Nitrogen Stress

Maize plants respond to low-nitrogen stress by enhancing root elongation. The underlying physiological mechanism remains unknown. Seedlings of maize （Zea mays L., cv. Zhengdan 958） were grown in hydroponics with the control （4 mmol L-1） or low-nitrogen （40 μmol L-1） for 12 d, supplied as nitrate. Low nitrogen enhanced root elongation rate by 4.1-fold, accompanied by increases in cell production rate by 2.2-fold, maximal elemental elongation rate （by 2.5-fold）, the length of elongation zone （by 1.5-fold）, and ifnal cell length by 1.8-fold. On low nitrogen, the higher cell production rate resulted from a higher cell division rate and in fact the number of dividing cells was reduced. Consequently, the residence time of a cell in the division zone tended to be shorter under low nitrogen. In addition, low nitrogen increased root diameter, an increase that occurred speciifcally in the cortex and was accompanied by an increase in cell number. It is concluded that roots elongates in response to low-nitrogen stress by accelerating cell production and expansion.

Untangling the influence of soil moisture on root pullout property of alfafa plant

Root pullout property of plants was of key importance to the soil reinforcement and the improvement of slope stability. To investigate the influence of soil moisture on root pullout resistance and failure modes in soil reinforcement process, we conducted pullout tests on alfalfa(Medicago sativa L.) roots at five levels(40, 30, 20, 10 and 6 kPa) of soil matric suction, corresponding to respectively 7.84%, 9.66%, 13.02%, 19.35% and 27.06% gravimetric soil moisture contents. Results showed that the maximal root pullout force of M. sativa decreased in a power function with increasing soil moisture content from 7.84% to 27.06%. Root slippage rate increased and breakage rate decreased with increasing soil moisture content. At 9.66% soil moisture content, root slippage rate and breakage rate was 56.41% and 43.58%, respectively. The threshold value of soil moisture content was about 9.00% for alfalfa roots in the loess soil. The maximal pullout force of M. sativa increased with root diameter in a power function. The threshold value of root diameter was 1.15 mm, because root slipping force was greater than root breaking force when diameter >1.15 mm, while diameter ≤1.15 mm, root slipping force tended to be less than root breaking force. No significant difference in pullout forces was observed between slipping roots and breaking roots when they had similar diameters. More easily obtained root tensile force(strength) is suggested to be used in root reinforcement models under the condition that the effect of root diameter is excluded as the pullout force of breaking roots measured in pullout tests is similar to the root tensile force obtained by tensile tests.

The inf luence of soil drying- and tillage-induced penetration resistance on maize root growth in a clayey soil

Soil drying may induce a number of stresses on crops. This paper investigated maize（Zea mays L.） root growth as affected by drought and soil penetration resistance（PR）, which was caused by soil drying and tillage in a clayey red soil. Compared with conventional tillage（C） and deep tillage（D）, soil compaction（P） and no-till（N） significantly increased soil PR in the 0-15 cm layer. The PR increased dramatically as the soil drying increased, particularly in soil with a high bulk density. Increased soil PR reduced the maize root mass density distribution not only in the vertical profile（0-20 cm） but also in the horizontal layer at the same distance（0-5, 5-10, 10-15 cm） from the maize plant. With an increase in soil PR in pots, the maize root length, root surface area and root volume significantly decreased. Specifically, the maize root length declined exponentially from 309 to 64 cm per plant with an increase in soil PR from 491 to 3 370 k Pa; the roots almost stopped elongating when the soil PR was larger than 2 200 k Pa. It appeared that fine roots（〈2.5 mm in diameter） thickened when the soil PR increased, resulting in a larger average root diameter. The average root diameter increased linearly with soil PR, regardless of soil irrigation or drought. The results suggest that differences in soil PR caused by soil drying is most likely responsible for inconsistent root responses to water stress in different soils.

Dose of Paclobutrazol in the Growth of Sugarcane Seedlings <i>in Vitro</i>in the Acclimatization Stage

Micropropagation has been widely used for the rapid multiplication of many plant species, where the final quality of the plant depends on the acclimatization stage. To obtain compact plants, with desired characteristics and adaptable to field conditions, the use of chemical inhibitors of growth is necessary. In sugarcane of the variety CP 72-2086 the effects caused by the growth regulator paclobutrazol (PBZ) in vitro plants applied in the acclimatization phase are unknown. The objective of this research was to know the effect of paclobutrazol in the acclimatization phase in the growth and development of the vitro plants of sugarcane of the variety CP 72-2086. The research was carried out in the greenhouse of the Faculty of Agronomy of the Autonomous University of Sinaloa, located at 24°37'29"N and 107°26'36"W, in Sinaloa, Mexico. Micro-propagated sugarcane seedlings were used by tissue culture;vitro plants were extracted from the flasks 24 hours before being transplanted into the greenhouse. The treatments of PBZ applied were the doses of 0 (control), 100, 150, 200, 250 and 300 mg·L-1. The PBZ was applied when the seedlings had seven true leaves [(31 days after transplant (ddt)], and did not show gutting. At 36 ddt, the vitro plants of the trays were extracted and the variables evaluated were height (cm), stem diameter (mm), root length (cm), root volume (mL), root dry weight (g), aerial biomass dry weight (g), leaf area (cm2) and greenness in spad units. A randomized complete block design with three replicates was used. The results of the study indicated that the dose of 150 g·L-1 of PBZ induced the growth of plants more compact and of better quality for the transplant.

On the Distribution Property of LehmerDH Number

This paper is to study the distribution property of Lehmer DH number by usethe estimation of general Kloostermann sum and the estimation of trigonometric sum.Key words: Lehmer DH number; primitive root; distribution property; Kloostermann sum;asymptotic

Variations in fine root dynamics and turnover rates in five forest types in northeastern China

Quantifying fi ne root(≤ 2.0 mm in diameter) distribution and turnover is essential for accurately estimating forest carbon budgets. However, fi ne root dynamics are poorly understood, possibly because of their inaccessibility. This study quantifi es fi ne root distribution and turnover rates for fi ve representative Chinese temperate forests types. Fine root number, diameter, biomass, necromass, production, mortality, and turnover rates were measured using a minirhizotron over a 12-month period. More than 90% of the fi ne roots were < 0.5 mm in diameter, with thin fi ne roots at shallow layers, and thicker ones in deeper soil layers. The fi ne root dynamics were signifi cantly diff erent among the forest types. Coniferous plantations had fewer fi ne roots, less biomass, necromass, production and mortality but greater average diameters than fi ne roots of broadleaved forests. All traits, except for diameter, decreased along the soil profi le. Fine root numbers and production exhibited a unimodal seasonal pattern with peaks occurring in summer, whereas biomass, necromass and mortality progressivelyincreased over the growing season. The turnover rates of roots < 0.5 mm varied from 0.4 to 1.0 a-1 for the fi ve forest types, 0.5–1.0 a-1 for the soil layers and 0.2–1.1 a-1 for the seasons, with the largest turnover rate at the 0–10 cm depth in summer. The patterns of fi ne root numbers, biomass, necromass, production, mortality, and turnover rates varied with forest types, soil depths, growing season and diameter classes. This study highlights the importance of forest types and diameters in quantifying fi ne root turnover rates.

Growth performance and scale insect infestation of Shorea leprosula in a common garden experimental plot

Many tree planting programmes have long been initiated to increase forest cover to mitigate the effects of global climate change.Successful planting requires careful planning at the project level,including using suitable species with favourable traits.However,there is a paucity of improvement data for tropical tree species.An experimental common garden of Shorea leprosula was established to study traits related to growth performance which are key factors in planting success.Seedlings of S.leprosula were collected from nine geographical forest reserves.To study the effects of genetic variation,seedlings were planted in a common environment following a randomized complete block design.From performance data collected 2017‒2019,one population showed the highest coefficient for relative height growth,significantly higher than most of the other populations.Interestingly,this population from Beserah also exhibited the lowest coefficient for scale insect infestation.This study provides preliminary results on growth performance and susceptibility to scale insect infestation in S.leprosula and the first common garden experiment site conducted on dipterocarp species.It lays a foundation for future genome-wide studies.

3D MERGE与3D SPACE STIR序列在腰椎间盘突出症检查中的应用比较

目的:对比三维多回波恢复梯度回波(3D MERGE)、三维可变反转角快速自旋回波(3D SPACE STIR)序列在腰椎间盘突出症(LDH)检查中的应用效果。方法:选择2020年1月~2022年11月收治的135例LDH患者,回顾性分析患者临床和磁共振成像(MRI)资料,所有患者均接受常规MRI扫描及3D MERGE、3D SPACE STIR序列扫描,对比3D MERGE、3D SPACE STIR序列测量神经根直径的一致性,评价两种序列的图像质量参数[信噪比(SNR)、对比噪声比(CNR)]、图像清晰度评分。结果:3D MERGE和3D SPACE STIR序列测量的L3~S1神经根直径比较差异无统计学意义(P>0.05),且两组序列测量的L3、L4、L5和S1直径均显示出较高相关性(r=0.957,0.986,0.975,0.972,P<0.05);3D MERGE序列的SNR及CNR均高于3D SPACE STIR序列,神经根显示分级、图像清晰度评分优于3D SPACE STIR序列,差异有统计学意义(P<0.05)。结论:3D MERGE、3D SPACE STIR序列在LDH神经根直径测量中具有极高一致性,3D MERGE序列较3D SPACE STIR序列能够更清晰显示神经跟的解剖形态,图像质量更好。

特征多项式系数的多种解析

利用矩阵特征多项式系数,可以帮助解决许多矩阵求解问题.因此,现有许多从某一方面出发、围绕特征多项式系数展开的研究.研究从多方面对特征多项式的系数特点做出了分析归纳,分别用矩阵的k阶主子式的和、矩阵的特征值、矩阵乘积的迹及矩阵A的次幂的迹表示特征多项式系数,得出了规律性的结论,同时对与特征多项式系数有着密切联系的牛顿等幂和公式给出了证明.

激素不同浓度在一定时间下对白牛槭嫩枝扦插生根的影响

采用激素NAA、IBA,浓度0、500、1 000、1 500 mg/L,时间0、5、10、15 min,以2年生白牛槭嫩枝作为试验材料研究其扦插技术,探讨激素和浓度在一定时间下对白牛槭嫩枝扦插生根的影响。试验中发现9号处理生根数最多,用相同浓度IBA1 000 mg/L+NAA1 000 mg/L速蘸5 min,白牛槭生根数最大值85(条),比6号处理在相同浓度IBA500 mg/L+NAA500 mg/L作用下速蘸5 min,生根数最小值3.33(条)大2 452.5%,比白牛槭14个处理根数平均值25.53(条)大232.9%;3号处理根长最长,用不同浓度IBA500 mg/L+NAA1 000 mg/L速蘸10 min,白牛槭根长最大值11.03 cm,比14号处理在不同浓度IBA1 000 mg/L+NAA500 mg/L速蘸5 min,根长最小值1.8 cm大512.7%,比14个处理根长平均值7大57.57%;2号处理根径的粗度最大,用不同浓度IBA0 mg/L+NAA1 000 mg/L速蘸10 min,白牛槭根径最大值1.78 mm,比14号处理在不同浓度IBA1 000 mg/L+NAA500 mg/L速蘸10 min,根径最小值0.49 mm大263.3%,比14个处理根径平均值0.67 mm大165.7%。因此,9号处理在相同激素浓度和相同时间、3号处理和2号处理在不同激素浓度和不同时间处理下,白牛槭嫩枝扦插生根数、生根长和生根茎的粗度数值都是最大(85条、11.03 cm、1.78 mm),生长表现最好。

吉林省立木材积出材率表编制技术方案的研究

从样木的选取单位、要求与数量,到外业调查方法、内业立木材积、出材率表的计算方法与验证,以及最终形成立木材积、出材率表等方面,系统阐述吉林省立木材积、出材率表的编制过程,以期为全国各地编制立木材积、出材率表提供借鉴。

Application of bi-directional static loading test to deep foundations

Bi-directional static loading test adopting load cells is widely used around the world at present, with increase in diameter and length of deep foundations. In this paper, a new simple conversion method to predict the equivalent pile head load-settlement curve considering elastic shortening of deep foundation was put forward according to the load transfer mechanism. The proposed conversion method was applied to root caisson foundation in a bridge and to large diameter pipe piles in a sea wind power plant. Some new load cells, test procedure, and construction technology were adopted based on the applications to different deep foundations, which could enlarge the application scopes of bi-directional loading test. A new type of bi-directional loading test for pipe pile was conducted, in which the load cell was installed and loaded after the pipe pile with special connector has been set up. Unlike the conventional bi-directional loading test, the load cell can be reused and shows an evident economic benefit.

Effect of water extracts of larch on growth of Manchurian walnut seedlings

研究被进行从象根那样的不同部分检测水摘录的效果，吠叫，分叉并且长叶，在二树种之间的成年落叶松， Larix gmelini，核桃树长果核桃树的生长上的树， Juglans mandshurica，幼苗和他感酌。四集中(100g · k g^(-1), 50 g · k g^(-1), 25 g · k g^(-1) 和 12.5 g · k g^(-1)) 为每种摘录作好准备。结果证明有低、中等的集中的水摘录加速了领子直径的生长并且增加了生物资源和核桃幼苗的根 / 射击比率。水从树枝提取并且与低、中等的集中吠叫加速了幼苗的高度生长，当那些稍微从叶子和根减少了时幼苗的高度生长。水的申请落叶松提取的事实可能改进了核桃树长果核桃树属性的生长到在二树种之间的他感酌。

Variations in root chemistry of three common forest species,southwestern China

Root chemistry varies with tree species and root diameter but little information is available about Tibetan forest species. The root chemistry of three root diameter classes (fine: 0–2 mm, medium: 2–5 mm, coarse: 5–10 mm) of three subalpine species (Abies faxoniana Rehd. and Wild, Picea asperata Mast., and Betula albosinensis Burkill) were investigated. Carbon concentrations, and carbon/nitrogen and carbon/phosphorus ratios increased but nitrogen, phosphorus and nitrogen/phosphorus ratios decreased with increasing root diameter. The roots of the conifers had higher carbon levels, and higher carbon/nitrogen and carbon/phosphorus ratios than birch roots. The opposite was found with nitrogen and phosphorus levels and nitrogen/phosphorus ratios. Lignin concentrations decreased but cellulose concentrations increased with greater root diameters. The results indicate that diameter-associated variations in root chemistry may regulate their contribution to detrital pools which has important implications for below-ground carbon and nutrient cycles in these subalpine forests.

Root Morphology and Anatomy of Field-Grown Erianthus arundinaceus

Erianthus species are perennial C4 grasses with such high biomass productivity and high tolerance to environmental stresses that they can be grown in marginal land to supply raw material for cellulosic bioethanol. Because high biomass production and strong tolerance to environmental stresses might be based on their large and deep-root system, we closely examined the morphology and anatomy of roots in first-year seedlings of field-grown Erianthus arundinaceus. The deep-root system of E. arundinaceus consists of many nodal roots growing with steep growth angles. Diameter of nodal roots with large variations (0.5 - 5 mm) correlates with the size and number of large xylem vessels. The microscopic observation shows that the nodal roots with dense root hairs developed soil sheath, hypodermis with lignified sclerenchyma in the outer cortex, and aerenchyma in the mid-cortex. In addition, starch grains were densely accumulated in the stele of nodal roots in winter. In the first year, E. arundinaceus developed less lateral roots than other reported grass species. The lateral roots formed a large xylem vessel in the center of the stele and no hypodermis in the outer cortex. Morphology and anatomy of E. arundinaceus root were discussed with reference to strong tolerance to environmental stresses.

Variation in Seed Germination and Seedling Growth in Five Populations of <i>Vitellaria paradoxa</i>C.F. Gaertn. Subsp. <i>Nilotica</i>in Uganda

We studied seed germination and seedling growth performance in an economically and socially important fruit tree species Vitellaria paradoxa C.F. Gaertn. subsp. nilotica (shea tree) in Uganda. The study aimed at determining variations in germination among five shea tree seed provenances and seedling growth performance based on five growth traits (total height, root collar diameter, leaf length, leaf width and leaf petiole length). Five populations were considered from four agroecological zones comprising of 180 candidate “plus” trees. The seed trees consisted of 16 ethnovarieties selected based on their traits for fast growth and high oil yield. A total of 1,204 biological seeds were collected and sown in a tree nursery at Ngetta Zonal Agricultural Research and Development Institute during the month of June 2018 in a randomized incomplete block design with three replications. Significant variation (χ = 708;p < 0.01) was observed in seedling phenotypic traits within and between populations. Regression equation for height growth and leaf size index were given as y = 0.3787 + 12.671x and y = 0.6483 + 15.413x respectively. Root collar diameter was more correlated to leaf size index (0.425) than to height growth (0.30). Clustering of shea tree seedlings based on phenotypic growth traits revealed one aggregated cluster indicating that most of the seedlings from the five populations were similar (Jaccard index 0.92, p < 0.01). However, clustering based on SNP markers revealed three different populations. We recorded higher growth (χ = 708;p < 0.001) in Arua shea population. Red seeded;thin pulped and hairy fruited shea tree ethnovarieties recorded faster growth than the rest. The results reveal useful traits in selection for tree growth and further identified shea tree ethnovarieties that could be selected for fast growth.

紫花苜蓿根系抗拉力学特性及其影响因素研究

为分析草本植物单根的抗拉力学特性及其影响因素,以紫花苜蓿为研究对象,选取不同根系直径、根系长度的紫花苜蓿根系在不同加载速率下开展室内单根拉伸试验,定量分析紫花苜蓿单根抗拉力学特性及其在不同影响因素下的变化规律。结果表明:加载速率对紫花苜蓿根系抗拉力和抗拉强度具有极显著影响(P<0.05),且在根系直径<3 mm时,加载速率为500 mm·min^(-1)时根系抗拉力和抗拉强度最大,而当根系直径相对较粗时,加载速率为100 mm·min^(-1)时根系抗拉力和抗拉强度最大;根系长度与紫花苜蓿根系抗拉力、抗拉强度之间没有显著差异(P>0.05);紫花苜蓿根系直径对根系抗拉力和抗拉强度具有显著影响(P<0.001),其与根系抗拉力呈幂函数正相关关系(R2=0.380,P<0.001),与抗拉强度呈幂函数负相关关系(R2=0.363,P<0.001);通过对紫花苜蓿根系抗拉力学特性的影响因素进行多元线性回归分析,根系直径是影响植物根系抗拉力学特性的最主要因素。

早播对新疆阿魏一年生种苗质量的影响

[目的]以新疆阿魏(Ferula sinkiangensis K.M.Shen)种子为试验材料,研究早播对新疆阿魏一年生种苗质量的影响。[方法]将种子层积处理后,分早播和常规播种2种处理,待种苗进入休眠后将根挖出,以根的重量、长度、宽度为指标评价种苗质量。[结果]早播较常规播种根重、根长、根粗分别增加251.57%、60.06%、40.52%,以根重为参考,早播种苗中有17.65%达到一级、10.29%达到二级、22.06%达到三级,而常规播种中没有能达到一级和二级的,仅有2.25%达到三级,其余未入级。[结论]适时早播能够有效提高新疆阿魏一年生种苗的质量。

空气修根对3个油茶品系生长的影响

为探究空气修根技术对不同油茶Camellia oleifera品系嫁接苗生长及根系发育的影响,以1 a生油茶嫁接苗为研究对象,以无纺布袋为试验容器,采用空气修根技术处理根部,定植土壤1 a后,比较油茶裸根苗和空气修根苗成活率、苗高、地径、叶面积、根系形态及各部位生物量的差异,分析空气修根对苗木生长和根系发育的影响。结果表明:(1)空气修根提高油茶苗成活率。(2)空气修根促进油茶苗高、地径、叶面积生长,涨幅分别为2.28%~22.73%、0.33%~35.96%、0.89%~2.99%。(3)空气修根刺激根长度生长,涨幅33.25%~232.32%,增加d>0.5 mm根数量、d≤0.5 mm根数量、根表面积和体积,增幅分别为8.33%~20.00%、83.41%~103.43%、43.53%~242.82%、77.16%~277.11%。(4)空气修根提高油茶地下、地上部分生物量累积,增加根冠比。综上所述,空气修根刺激侧根生长,增加侧根数量和生物量,提高油茶造林成活率,有利于油茶容器苗工厂化培育和推广应用。