Plant functional traits and soil microbial biomass in different vegetation zones on the Loess Plateau

Plant functional traits built the relationships between plant diversity, species composition, and physiology along with the environmental changes, thus influencing soil microbial community. As the sensitivity indicators, soil microbial biomass and plant functional traits responses soil micro-organism and plant characteristics in direct way. Ten plant functional traits of 149 species and soil microbial biomass (carbon, nitrogen, and phosphorus) were analyzed across the different vegetation types (forest, forest-steppe, and steppe) that are divided by environmental gradient (temperature and precipitation), aimed to find the correlations among them. Our results confirmed the greatest values of plant functional traits (except the leaf density and the fine root density) that were distributed in the steppe zone, mainly due to the different mean annual temperature and mean annual precipitation conditions. For different plant growth forms, the plant functional traits were significant differences among the vegetation zones. The advantages of higher rate nutrient cycling, plentiful biomass supplements, and favorite habit conditions lead to the forest-steppe zone with the highest C_mic and N_mic concentrations. The canonical correlation analysis indicated that leaf nitrogen, root nitrogen, and fine root densities were correlated with root exudate and tissue which affected the concentrations of soil organic carbon (SOC) and total nitrogen (N), consequently impacting soil microbial biomass carbon (C_mic) and soil microbial biomass nitrogen (N_mic). Soil is the medium that connects micro-organism and plant root system that influenced leaf nitrogen, root nitrogen, and fine root density of plant functional traits, the concentrations of SOC and total N that plant feedback are consequently influencing C_mic and N_mic.     

Shoot RNA, cambrial activity and indolebutyric acid effectivity in seasonal rooting of juvenile and mature Ficus pumila cuttings

The seasonal influence on adventitious root formation was studied in woody leaf bud cuttings of Ficus pumila L., creeping fig. Juvenile cuttings rooted easily, whereas only mature cuttings treated with indolebutyric acid (IBA) exceeded 30% rooting. Greater rooting occurred in IBA-treated juvenile and mature cuttings than controls, regardless of the month each experiment was initiated. Seasonal changes influenced rooting in all treatments except IBA treated juvenile cuttings where percentage rooting was not affected. Higher vascular cambial activity and shoot RNA levels occurred in juvenile and mature forms during peak rooting periods. Highest RNA was recorded with juvenile materials during maximum rooting periods, while lowest RNA was observed in mature shoots during low rooting intervals.     

Size dependence of leaf area and the mass of component organs during a course of self-thinning in a hinoki (Chamaecyparis obtusa) seedling population

The allometric equation, y=gx^h, was applied monthly to the relationships between two different dimensions of tree seedlings of hinoki cypress (Chamaecyparis obtusa) during a course of self-thinning from April 1990 to March 1991 to detect differences in biomass allocation among individuals. As the h-value in the allometry of crown length and seedling height was greater than unity for all seasons, crown ratio became greater as seedling height increased. Leaf weight ratio increased with increasing seedling size because the h-value in the allometry of leaf dry weight and whole seedling dry weight was greater than unity in every month. Therefore, smaller seedlings are disadvantageous to photosynthetic production by leaves. In contrast, the leaf area ratio was constant irrespective of seedling size because the h-value in the allometry of leaf area and whole seedling dry weight was nearly equal to unity in most seasons. In addition, because the h-value in the allometry of leaf area and leaf dry weight was less than unity in all seasons, specific leaf area decreased with an increase in leaf dry weight, indicating that smaller seedlings adapt to low light environments by possessing shade leaves. Root weight ratio decreased with increasing seedling size because the h-value in the allometry of root dry weight and whole seedling dry weight was less than unity in most seasons.     

Responses of root length/leaf area ratio and specific root length of an understory herb, Pteridophyllum racemosum, to increases in irradiance

The understory evergreen perennial Pteridophyllum racemosum Sieb. et Zucc. (Papaveraceae) has the ability to increase root mass per unit transpiring leaf area (RMA) if irradiance increases gradually over several years. In this study, we examined how P. racemosum changes its root length/leaf area ratio and specific root length when the species encounters abrupt increases in irradiance, such as sudden and unexpected canopy openings. Plants were transplanted from a low light condition in a subalpine wave-regenerating forest (photon flux density on the forest floor relative to the full sun (RPFD) was 2.7%) to a high light condition in a glasshouse (30% RPFD) (LH treatment). Transplantation from the low light condition in the forest to a low light condition in the glasshouse (LL) and transplantation from a high light condition in the forest (33% RPFD) to a high light condition in the glasshouse (HH) were also conducted as controls. Compared to the LL plants, the LH plants exhibited significant increases in RMA and root length/leaf area ratio from 30 to 70 days after transplantation. On the other hand, the effect of increased irradiance on specific root length (SRL) was weak, and both the LL and LH plants showed increased SRL from 30 to 70 days after transplantation. Increased SRL results from longer root length per unit construction cost. We concluded that increased root length/leaf area ratio of P. racemosum in response to abrupt increases in irradiance was caused by a combination of enhanced carbon allocation to roots with increased SRL.     

Development of phosphogluco-isomerase isozymes in perennial ryegrass (Lolium perenne)

The development of isozymes of phosphogluco-isomerase (PGI; D-glucose-6-phosphate ketol isomerase EC 5.3.1.9.) in perennial ryegrasses was followed from dry seed through to leaf senescence using starch gel electrophoretic separations. Root isozymes were also examined. Two forms of the enzyme were found, one (PGI/2) being present in all tissues and at all stages of the life cycle. The other (PGI/1) had two zones of activity, one of which was detected only in light-exposed tissue. Normal development of this form could be inhibited by growing seedlings on distilled water. Some alleles of PGI/2 not previously reported for ryegrasses are also described.     

中华水韭根叶发育的解剖观察

中华水韭(Isoetes sinensis Palmer)为国家一级保护野生植物,被评价为极度濒危级(CR),仅分布在长江中下游,对环境污染敏感。本文以其人工苗为材料,用石蜡切片法,连续观察了根和叶的发育特征:叶原基横切面呈端部渐圆的三角形,由表皮原、皮层原和中柱原三部分组成;维管束中央首先出现的一个原生管胞,与其近轴面两侧后出现的两个后生管胞共同组成倒“V”字型的外始式初生木质部;成熟叶分化出表皮与皮层,表皮细胞间有嵌合,皮层部分细胞裂解成彼此不相通的4个通气道。根横切面呈圆形,成熟区分化出表皮、皮层(外皮层、中皮层、内皮层)和维管束三部分,中皮层部分细胞裂解呈一个完整的筒状通气道并与外皮层无连接,由内皮层包围的维管束横切面呈三角形。讨论了根和叶的形态结构、功能及系统学意义。     

Leaf and fine root carbon stocks and turnover are coupled across Arctic ecosystems

Estimates of vegetation carbon pools and their turnover rates are central to understanding and modelling ecosystem responses to climate change and their feedbacks to climate. In the Arctic, a region containing globally important stores of soil carbon, and where the most rapid climate change is expected over the coming century, plant communities have on average sixfold more biomass below ground than above ground, but knowledge of the root carbon pool sizes and turnover rates is limited. Here, we show that across eight plant communities, there is a significant positive relationship between leaf and fine root turnover rates (r² = 0.68, P < 0.05), and that the turnover rates of both leaf (r² = 0.63, P < 0.05) and fine root (r² = 0.55, P < 0.05) pools are strongly correlated with leaf area index (LAI, leaf area per unit ground area). This coupling of root and leaf dynamics supports the theory of a whole‐plant economics spectrum. We also show that the size of the fine root carbon pool initially increases linearly with increasing LAI, and then levels off at LAI = 1 m² m^?2, suggesting a functional balance between investment in leaves and fine roots at the whole community scale. These ecological relationships not only demonstrate close links between above and below‐ground plant carbon dynamics but also allow plant carbon pool sizes and their turnover rates to be predicted from the single readily quantifiable (and remotely sensed) parameter of LAI, including the possibility of estimating root data from satellites.     

Influence of substrate and burial on the development of Posidonia oceanica: implications for restoration

Posidonia oceanica is one of the few seagrasses that can colonize hard and soft substrates. To test whether substrate could affect root development of the seedlings, with a legacy effect upon transplantation to sand, we germinated seeds on hard (glass slide) versus soft (sand) substrates in microcosms. We found that sand favored root system development, with a compensatory slowing of leaf development, while glass had the opposite effect. After 4 months, we transplanted all seedlings to sand and tested for a legacy effect of initial substrate type. Leaves of seedlings germinated on sand and glass slides reached approximately the same length, but roots from seedlings germinated on glass did not develop fully. Seed burial (0–1.5 cm) did not affect seedling development. These results suggest that the culture of P. oceanica on sand prior to transplantation could enhance seedlings survival in restoration programs.     

金线莲与台湾金线莲显微结构比较

通过石蜡切片和表皮制片观察比较金线莲Anoectochilus roxburghii和台湾金线莲A.formosanus根、茎、叶的显微结构特征。结果表明,金线莲与台湾金线莲显微结构的主要区别在于根皮层厚度、维管束数目、叶构造、叶脉颜色、表皮乳头细胞的形状和气孔密度,这些特征可作为金线莲物种的显微鉴别依据。     

Partitioning of dry mass and leaf area within plants of three species grown at elevated CO2

1. We tested the hypothesis that the net partitioning of dry mass and dry mass:area relationships is unaltered when plants are grown at elevated atmospheric CO₂ concentrations.
2. The total dry mass of Dactylis glomerata, Bellis perennis and Trifolium repens was higher for plants in 700 compared to 350 μmol CO₂ mol^–1 when grown hydroponically in controlled-environment cabinets.
3. Shoot:root ratios were higher and leaf area ratios and specific leaf areas lower in all species grown at elevated CO₂. Leaf mass ratio was higher in plants of B. perennis and D. glomerata grown at elevated CO₂.
4. Whilst these data suggest that CO₂ alters the net partitioning of dry mass and dry mass:leaf area relationships, allometric comparisons of the components of dry mass and leaf area suggest at most a small effect of CO₂. CO₂ changed only two of a total of 12 allometric coefficients we calculated for the three species: ν relating shoot to root dry mass was higher in D. glomerata , whilst ν relating leaf area to total dry mass was lower in T. repens .
5. CO₂ alone has very little effect on partitioning when the size of the plant is taken into account.     

Salt effects on functional traits in model and in economically important Lotus species

A common stress on plants is NaCl‐derived soil salinity. Genus Lotus comprises model and economically important species, which have been studied regarding physiological responses to salinity. Leaf area ratio (LAR), root length ratio (RLR) and their components, specific leaf area (SLA) and leaf mass fraction (LMF) and specific root length (SRL) and root mass fraction (RMF) might be affected by high soil salinity. We characterised L. tenuis, L. corniculatus, L. filicaulis, L. creticus, L. burtii and L. japonicus grown under different salt concentrations (0, 50, 100 and 150 mm NaCl) on the basis of SLA, LMF, SRL and RMF using PCA. We also assessed effects of different salt concentrations on LAR and RLR in each species, and explored whether changes in these traits provide fitness benefit. Salinity (150 mm NaCl) increased LAR in L. burtii and L. corniculatus, but not in the remaining species. The highest salt concentration caused a decrease of RLR in L. japonicus Gifu, but not in the remaining species. Changes in LAR and RLR would not be adaptive, according to adaptiveness analysis, with the exception of SLA changes in L. corniculatus. PCA revealed that under favourable conditions plants optimise surfaces for light and nutrient acquisition (SLA and SRL), whereas at higher salt concentrations they favour carbon allocation to leaves and roots (LMF and RMF) in detriment to their surfaces. PCA also showed that L. creticus subjected to saline treatment was distinguished from the remaining Lotus species. We suggest that augmented carbon partitioning to leaves and roots could constitute a salt‐alleviating mechanism through toxic ion dilution.     

亚热带六种天然林树种细根养分异质性

以福建省建瓯市万木林自然保护区常绿阔叶林6种优势树种为研究对象,分析其1—5级细根养分特征及其与细根形态特征和叶片养分的关系。结果发现:除沉水樟细根C含量表现为随序级升高而增加外,其余5种树种均没有明显变化规律;6种树种N、P含量基本表现为随序级升高而降低,C/N随序级升高而增加;但N/P随序级升高均没有明显变化规律。单因素方差分析发现:树种对C、N、P含量和C/N、N/P具有极显著影响(P<0.01),序级对6种树种N、P含量和C/N有极显著或显著影响(P<0.01,P<0.05),对C含量和N/P影响并不显著(P>0.05);双因素方差分析发现:树种和序级的交互作用对C、N、P含量和C/N有极显著或显著的影响(P<0.01,P<0.05),对N/P影响不显著(P>0.05)。相关性分析表明:在较高级根中C、N含量之间呈现相关性,在较低级根中N、P含量呈现相关性,同时C/N、N/P的变化均主要由N含量变化决定;6种树种细根比根长和N、P含量、C/N有极显著相关性(P<0.01),而与C含量和N/P相关性并不明显。一级根的N、P含量和N/P相比于整个细根更接近于叶片,但一级根与叶片N、P、N/P之间并没有显著的相关性(P>0.05)。     

Allometry, root/shoot ratio and root architecture in understory saplings of deciduous dicotyledonous trees in central Japan

Plant allometry that is related to plant architecture and biomass allocation strongly influences a plants ability to grow in shaded forest understory. Some allometric traits can change with plant size. The present study compared crown and trunk allometries, root/shoot biomass allometry, and root architecture among understory saplings (0.25--5m height, except for two trees > 5 < 7 m) of seven deciduous dicotyledonous species in central Japan. Associations of the crown and trunk allometries with several plant morphological attributes were analyzed. Branch morphology (plagiotropyvs orthotropy) and life size were correlated with sapling crown and trunk allometries. Both large leaves and orthotropic branches were associated with a narrow small crown and slender trunk. The root/shoot ratio decreased rapidly with increasing plant height for saplings shorter than about 1.5 m. Less shade-tolerant species tended to have smaller root/shoot ratios for saplings taller than 1.5 m. With an increase in plant height, the branch/trunk biomass ratio decreased for saplings with plagiotropic branches but increased for saplings with orthotropic branches. Four subcanopy species (Acer distylum, Carpinus cordata, Fraxinus lanuginosa and Acanthopanax sciadophylloides) had superficial root systems; a common understory species (Sapium japonica) had a deep tap root system; and a canopy species (Magnolia obovata) and a subcanopy species (Acer tenuifolium) had heart root systems of intermediate depth. The root depth was not related to shade tolerance. Among species of the same height, the difference in fine root length can be 30-fold.     

Sequence of drought response of maize seedlings in drying soil

Leaf elongation in monocotyledonous plants is sensitive to drought. To better understand the sequence of events in plants subjected to soil drying, leaf elongation and transpiration of maize seedlings ( Zea mays L.) of 4 cultivars were monitored continuously and the diurnal courses of the root and leaf water relations were determined. Results from this study indicate the following sequence of drought response: Leaf elongation decreased before changes in the leaf water relations of non‐growing zones of leaf blades were detected and before transpiration decreased. Reductions in leaf elongation preceded changes in the root water potential (ψ_w). Root ψ_w was not a very sensitive indicator of soil dryness, whereas the root osmotic potential (ψ_s) and root turgor (ψ_p) were more sensitive indicators. The earliest events observed in drying soil were a significant increase in the largest root diameter class (1 720 to 1 960 gm) and a decrease in leaf elongation ( P = 0.08) 2 days after withholding water. Significant increases in root length were observed 2 days later. Soil drying increased the number of fine roots with diameters of <240 µm. Slight increases in soil strength did not affect leaf elongation in the drying soil.     

The ambiguous role of 2,4-dichlorophenoxyacetic acid in wheat tissue culture

The very basal, highly immature regions of dissected young leaves of Triticum aestivum L. cv. Kite formed adventitious roots on a nutrient medium supplemented with comparatively low concentrations (0.16 to 0.63 μ M ) of 2,4-dichlorophenoxyacetic acid (2,4-D). Higher concentrations (up to 640 μ M ) had to be applied to stimulate growth from more mature regions higher up the leaf. Yet, already at 2.5 μ M roots were less distinct and more callus-like, and eventually (at 10 to 640 μ M ) only a subculturable callus of apparently suppressed, slowly proliferating root primordia developed. Furthermore, at the most basal, highly immature regions growth was significantly retarded when the auxin concentration was raised. The leaf culture system appears to reflect the dual action of 2,4-D known from herbicide research, namely growth stimulation from differentiating (or differentiated) cells, but growth suppression at or in the vicinity of apical meristems. Correspondingly, when the callus of apparently suppressed, slowly proliferating root primordia was transferred to media without 2,4-D or with low concentrations (0.16–2.5 μ M ) rapid proliferation commenced, leading to profuse root outgrowth. The system demonstrates the ambiguous role which this auxin appears to have, at least in wheat tissue culture.     

植被界面过程(VIP)模型的改进与验证

为了提高植被界面过程(VIP)模型的预报能力,对VIP模型的一些参数化方案进行了更新,包括基于相对生育期的根深动态、根系分布密度和比叶面积季节变化,使模型能从机理上更合理地描述作物同化物分配及土壤水分运动。将改进后的模型应用于河北栾城冬小麦生长季的叶面积指数、生物量和土壤水分模拟,并与相应时期的试验资料对比验证。结果表明,改进后的VIP模型对土壤水分动态和冬小麦叶面积指数的模拟效果更好,模型各状态变量模拟值与观测值的均方根误差和相关系数都得到明显提高。     

Linking leaf and root trait syndromes among 39 grassland and savannah species

Here, we tested hypothesized relationships among leaf and fine root traits of grass, forb, legume, and woody plant species of a savannah community. CO2 exchange rates, structural traits, chemistry, and longevity were measured in tissues of 39 species grown in long-term monocultures. Across species, respiration rates of leaves and fine roots exhibited a common regression relationship with tissue nitrogen (N) concentration, although legumes had lower rates at comparable N concentrations. Respiration rates and N concentration declined with increasing longevity of leaves and roots. Species rankings of leaf and fine-root N and longevity were correlated, but not specific leaf area and specific root length. The C3 and C4 grasses had lower N concentrations than forbs and legumes, but higher photosynthesis rates across a similar range of leaf N. Despite contrasting photosynthetic pathways and N2-fixing ability among these species, concordance in above- and below-ground traits was evident in comparable rankings in leaf and root longevity, N and respiration rates, which is evidence of a common leaf and root trait syndrome linking traits to effects on plant and ecosystem processes.     

麦套花生产量形成期固氮酶和保护酶活性特征研究

以小麦品种烟农23号"和花生品种花育22号"为材料,研究了大田条件下花生产量形成期套种和清种花生根瘤固氮酶活性及SOD、POD、CAT活性等指标变化情况.结果表明:(1)麦套和清种花生单株根瘤重量和固氮酶活性变化均呈单峰曲线,高峰期分别出现在结荚末期和结荚中期;前者固N能力明显高于后者.(2)花生根系中SOD、POD、CAT活性基本上均是先增后降趋势,但麦套花生后期下降速率明显缓于清种花生;叶片中SOD、POD、CAT活性变化规律性明显不及根系,后期麦套花生SOD、CAT活性高于清种花生,POD则相反.(3)麦套花生根系中可溶性蛋白含量一直较高,而清种花生后期下降较快;麦套花生叶片中可溶性蛋白含量的高峰约出现在结荚中期,清种花生整个结荚期呈下降态势,两者进入饱果期后均趋于稳定.可见麦套花生生育后期根系衰老速率明显迟于清种花生.     

Why is liana abundance low in semiarid climates?

Lianas are abundant in seasonal tropical forests, where they avoid seasonal water stress presumably by accessing deep‐soil water reserves. Although lianas are favoured in seasonal environments, their occurrence and abundance are low in semiarid environments. We hypothesized that lianas do not tolerate the great water shortage in the soil and air characteristic of semiarid environments, which would increase the risk of embolism. We compared the rooting depth of coarse roots, leaf dynamics, leaf water potential (ψ_leaf), embolism resistance (P₅₀) and lethal levels of embolism (P₈₈) between congeneric lianas that occur with different abundances in two semiarid sites differing in soil characteristics and vapour pressure deficit in the air (VPD_air). Regardless of soil texture and depth, water availability was restricted to the rainy season. All liana species were drought deciduous and had superficial coarse roots (not deeper than 35 cm). P₅₀ varied from ?1.8 to ?2.49 MPa, and all species operated under narrow safety margins against catastrophic (P₅₀) and irreversible hydraulic failure (P₈₈), even during the rainy season. In short, lianas that occur in semiarid environments have lower resistance to cavitation and limit carbon fixation to the rainy season because of leaf fall in the early dry season. We suggest that leaf shedding and shallow roots impairing carbon gain and growth in the dry season may explain why liana abundance is lower in semiarid than in other seasonally dry environments.