Effect of Globodera rostochiensis on the growth of reciprocal grafts between two potato cultivars of different tolerance in a field trial

The tolerance of plants produced from reciprocal grafts between cv. Cara and cv. Pentland Dell were compared in field plots containing different initial population densities of Globodera rostochiensis. Both stock and scion contributed to the greater tolerance of cv. Cara as compared with cv. Pentland Dell. Ground cover measurements, made by a novel photographic method, showed that a heavy infestation of G. rostochiensis decreased the top growth of all plants: more for those with scions of Pentland Dell than those with scions of Cara. The stock did not initially affect the extent to which top growth was reduced in the heavily infested plots but later measurements showed a progressively increased effect on top growth for plants with stocks of Pentland Dell and a decreased effect for those with Cara. In a destructive harvest 13 wk after planting the relatively small effect of G. rostochiensis on the top growth of plants with Cara scions was not reflected in the tuber yields which were markedly decreased. However, plants with Cara stocks were considerably more tolerant (i.e. tuber yields were affected less) than those with stocks of Pentland Dell. Overall, plants of Pentland Dell scions on Cara root stocks were most tolerant at this stage. Between 13 and 16 wk, when a second destructive harvest was made, plants with Pentland Dell scions were senescent and their yield increased little. In contrast, plants with Cara scions were still growing and their yield increased markedly so that by 16 wk the most tolerant combination was Cara on Cara.     

Testing for the Equality of the Variance-Covariance Matrices of Two Jointly Normal Vector Variables

Assume a joint 2P-variate normal distribution for the p-component vectors x and y with unknown mean and unknown variance-covariance matrices Σ_xx and Σ_yy respectively, with Cov (x , y )=Σ_xy. No assumptions are made about the nature of Σ_xy. The likelihood ratio method is investigated to test the hypothesis that Σ_xx = Σ_yy. A method of numerical solution to the likelihood equations in the restricted parameter case is given when p=2, and approximate solutions are suggested for p>2.     

Growth, light interception and yield responses of spring wheat (Triticum aestivum L.) grown under elevated CO2 and O3 in open-top chambers

Spring wheat cv. Minaret was grown to maturity under three carbon dioxide (CO₂) and two ozone (O₃) concentrations in open-top chambers (OTC). Green leaf area index (LAI) was increased by elevated CO₂ under ambient O₃ conditions as a direct result of increases in tillering, rather than individual leaf areas. Yellow LAI was also greater in the 550 and 680 μmol mol^–1 CO₂ treatments than in the chambered ambient control; individual leaves on the main shoot senesced more rapidly under 550 μmol mol^–1 CO₂, but senescence was delayed at 680 μmol mol^–1 CO₂. Fractional light interception (f) during the vegetative period was up to 26% greater under 680 μmol mol^–1 CO₂ than in the control treatment, but seasonal accumulated intercepted radiation was only increased by 8%. As a result of greater carbon assimilation during canopy development, plants grown under elevated CO₂ were taller at anthesis and stem and ear biomass were 27 and 16% greater than in control plants. At maturity, yield was 30% greater in the 680 μmol mol^–1 CO₂ treatment, due to a combination of increases in the number of ears per m^–2, grain number per ear and individual grain weight (IGW). Exposure to a seasonal mean (7 h d^–1) of 84 nmol mol^–1 O₃ under ambient CO₂ decreased green LAI and increased yellow LAI, thereby reducing both f and accumulated intercepted radiation by ≈ 16%. Individual leaves senesced completely 7–28 days earlier than in control plants. At anthesis, the plants were shorter than controls and exhibited reductions in stem and ear biomass of 15 and 23%. Grain yield at maturity was decreased by 30% due to a combination of reductions in ear number m^–2, the numbers of grains per spikelet and per ear and IGW. The presence of elevated CO₂ reduced the rate of O₃-induced leaf senescence and resulted in the maintenance of a higher green LAI during vegetative growth under ambient CO₂ conditions. Grain yields at maturity were nevertheless lower than those obtained in the corresponding elevated CO₂ treatments in the absence of elevated O₃. Thus, although the presence of elevated CO₂ reduced the damaging impact of ozone on radiation interception and vegetative growth, substantial yield losses were nevertheless induced. These data suggest that spring wheat may be susceptible to O₃-induced injury during anthesis irrespective of the atmospheric CO₂ concentration. Possible deleterious mechanisms operating through effects on pollen viability, seed set and the duration of grain filling are discussed.     

Non‐destructive allometric estimates of above‐ground and below‐ground biomass of high‐mountain vegetation in the Andes

Aim

Studies that monitor high‐mountain vegetation, such as paramo grasslands in the Andes, lack non‐destructive biomass estimation methods. We aimed to develop and apply allometric models for above‐ground, below‐ground and total biomass of paramo plants.

Location

The paramo of southern Colombia between 1°09′N and 077°50′W, at 3,400 and 3,700 m a.s.l.

Methods

We established 61 1‐m² plots at random locations, excluding disturbed, inaccessible and peat bog areas. We measured heights and basal diameters of all vascular plants in these plots and classified them into seven growth forms. Near each plot, we sampled the biomass from plants of abundant genera, after having measured their height and basal diameter. Hence, we measured the biomass of 476 plants (allometric set). For each growth form we applied power‐law functions to develop allometric models of biomass against basal diameter, height, height x basal diameter and height × basal area. The best models were selected using AIC_c weights. Using the observed and predicted plant biomass of the allometric set we calculated absolute percentage errors using cross‐validation. The biomass of a plot was estimated by summing the predicted biomass of all plants in a plot. Confidence limits around these sums were calculated by bootstrapping.

Results

For groups of <20 plants the biomass predictions yielded large (>15%) errors. Applying groups that resembled the 1‐m² plots in density and composition, the errors for above‐ground and total biomass estimates were <15%. Across all plots, we obtained an above‐ground, below‐ground and total plot biomass of 329 ± 190, 743 ± 486 and 1011 ± 627 g/m² (mean ± SD), respectively. These values were within the range of biomass estimates obtained destructively in the tropical Andes.

Conclusions

In new applications, if target vegetation samples are similar regarding growth forms and genera to our allometric set, their biomass might be predicted applying our equations, provided they contain at least 50–100 plants. In other situations, we would recommend gathering additional biomass measurements from local plants to evaluate new regression equations.     

Allometric growth relationships of East Africa highland bananas (Musa AAA-EAHB) cv. Kisansa and Mbwazirume

Highland bananas are an important staple food in East Africa, but there is little information on their physiology and growth patterns. This makes it difficult to identify opportunities for yield improvement. We studied allometric relationships by evaluating different phenological stages of highland banana growth for use in growth assessment, understanding banana crop physiology and yield prediction. Pared corms of uniform size (cv. Kisansa) were planted in a pest‐free field in Kawanda (central Uganda), supplied with fertilizers and irrigated during dry periods. In addition, tissue‐cultured plants (cv. Kisansa) were planted in an adjacent field and in Ntungamo (southwest Uganda), with various nutrient addition treatments (of N, P, K, Mg, S, Zn, B and Mo). Plant height, girth at base, number of functional leaves and phenological stages were monitored monthly. Destructive sampling allowed derivation of allometric relationships to describe leaf area and biomass distribution in plants throughout the growth cycle. Individual leaf area was estimated as LA (m²) = length (m) × maximum lamina width (m) × 0.68. Total plant leaf area (TLA) was estimated as the product of the measured middle leaf area (MLA) and the number of functional leaves. MLA was estimated as MLA (m²) = ?0.404 + 0.381 height (m) + 0.411 girth (m). A light extinction coefficient (k = 0.7) was estimated from photosynthetically active radiation measurements in a 1.0 m grid over the entire day. The dominant dry matter (DM) sinks changed from leaves at 1118 °C days (47% of DM) and 1518 °C days (46% of DM), to the stem at 2125 °C days (43% of DM) and 3383 °C days (58% of DM), and finally to the bunch at harvest (4326 °C days) with 53% of DM. The allometric relationship between above‐ground biomass (AGB in kg DM) and girth (cm) during the vegetative phase followed a power function, AGB = 0.0001 (girth)^2.35 (R² = 0.99), but followed exponential functions at flowering, AGB = 0.325 e^0.036(girth) (R² = 0.79) and at harvest, AGB = 0.069 e^0.068(girth) (R² = 0.96). Girth at flowering was a good parameter for predicting yields with R² = 0.7 (cv. Mbwazirume) and R² = 0.57 (cv. Kisansa) obtained between actual and predicted bunch weights. This article shows that allometric relationship can be derived and used to assess biomass production and for developing banana growth models, which can help breeders and agronomists to further exploit the crop's potential.     

不同放牧制度下呼伦湖流域草原植被冠层截留

冠层截留是降雨过程中的水量分配和流域水平衡的一个重要组成部分,通过水浸泡法和降雨模拟实验研究呼伦湖流域草原3种放牧制度下(休牧、轮牧、自由放牧(超载放牧))植被冠层截留量的变化规律,并利用遥感解译植被归一化指数(NDVI),确定3种放牧制度下草原面积,估算呼伦湖流域草原降雨截留量。研究表明:在休牧、轮牧、自由放牧3种制度下,水浸泡法测定的截留量分别是0.468、0.320、0.271 mm。降雨模拟实验法测得的结果分别是0.957、0.613、0.431 mm。休牧、轮牧、自由放牧草场叶面积指数、盖度、容重、生物量等指标差异显著(P0.05),且单株植被高度、鲜重对截留量影响显著呈线性正相关关系。呼伦湖流域草原一次降雨量为大于等于30 mm全流域降雨,其植被截留量为6.462×106m3。     

Interactive effects of elevated temperature and drought on plant carbon metabolism: A meta-analysis

Elevated temperature (T_e) and drought often co-occur and interactively affect plant carbon (C) metabolism and thus the ecosystem C cycling; however, the magnitude of their interaction is unclear, making the projection of global change impacts challenging. Here, we compiled 107 journal articles in which temperature and water availability were jointly manipulated, and we performed a meta-analysis of interactive effects of T_e and drought on leaf photosynthesis (A_growth) and respiration (R_growth) at growth temperature, nonstructural carbohydrates and biomass of plants, and their dependencies on experimental and biological moderators (e.g., treatment intensity, plant functional type). Our results showed that, overall, there was no significant interaction of T_e and drought on A_growth. T_e accelerated R_growth under well-watered conditions rather than under drought conditions. The T_e × drought interaction on leaf soluble sugar and starch concentrations were neutral and negative, respectively. The effect of T_e and drought on plant biomass displayed a negative interaction, with T_e deteriorating the drought impacts. Drought induced an increase in root to shoot ratio at ambient temperature but not at T_e. The magnitudes of T_e and drought negatively modulated the T_e × drought interactions on A_growth. Root biomass of woody plants was more vulnerable to drought than that of herbaceous plants at ambient temperature, but this difference diminished at T_e. Perennial herbs exhibited a stronger amplifying effect of T_e on plant biomass in response to drought than did annual herbs. T_e exacerbated the responses of A_growth and stomatal conductance to drought for evergreen broadleaf trees rather than for deciduous broadleaf and evergreen coniferous trees. A negative T_e × drought interaction on plant biomass was observed on species-level rather than on community-level. Collectively, our findings provide a mechanistic understanding of the interactive effects of T_e and drought on plant C metabolism, which would improve the prediction of climate change impacts.     

Shoot growth, radiation interception and dry matter production and partitioning during the establishment phase of Miscanthus sinensis'Giganteus' grown at two densities in the UK

Photosynthetic area index (PAI), radiation interception (I) and dry matter partitioning between shoots and roots were measured for Miscanthus sinensis‘Giganteus' grown from micro-propagated transplants on a fertile peaty loam soil in eastern England. In the establishment year, Miscanthus plants produced 35 and 70 shoots plant^-1 at densities of 4.0 and 1.8 plants m^-2 respectively. At the higher density, there were 140 shoots m^-2 with the largest reaching a height of 1.8 m; these canopies attained a maximum PAI of 5.45, intercepting 94% of incident radiation. Leaf lamina contributed c. 90% of total photosynthetic area with stems contributing the remainder. At the lower density, maximum PAI and I values were 2.88 and 86% respectively. PAI was related to I by calculating attenuation coefficients (k); these indicated that Miscanthus canopies were more effective at intercepting radiation per unit PAI at the lower density (k= -0.31) compared with the higher density (k= -0.20). Radiation interception was related to dry matter accumulated by calculating conversion efficiencies (e). At 4 plants m^-2, × for shoot dry matter production was 1.17g MJ^-1. Miscanthus partitioned a relatively large amount of total dry matter into below-ground biomass. By plant senescence, c. 30% of total dry matter had been partitioned into root and rhizome; rhizome biomass contributed 80% of below-ground dry matter, × increased to 1.62 g MJ^-1 when calculated on a total dry matter basis (shoot + root + rhizome). Total dry matter production was increased 68% by a 2.2-fold increase in plant density.     

The response of Vicia faba to enhanced UV-B radiation under low and near ambient PAR levels

The effects of enhanced UV-B are often overestimated in greenhouse studies due to low levels of photosynthetically active radiation (PAR). For this reason, we studied effects of enhanced UV-B (12 kJ m^–2 d^–1) at low and near ambient PAR levels on young vegetative plants of Vicia faba, in the greenhouse. It was hypothesized that near ambient PAR levels could reduce the negative UV-B effects on growth, due to higher amounts of UV-B absorbing compounds in the leaves and to morphological changes attenuating UV-B damage.We found that effects of enhanced UV-B on the growth were not negative. We found an increase in biomass in response to enhanced UV-B at low and near ambient PAR levels. The increase in biomass was related to increased branching, which leads to a higher interception of PAR. Enhanced irradiance of both PAR and UV-B had similar photomorphogenic effects: thicker and smaller leaves and reduced plant height and internode length. Moreover, the concentration of UV-B absorbing compounds was increased. We conclude that in this study effects of enhanced UV-B were mainly photomorphogenic effects, which were also induced by radiation in the PAR region.     

Will elevated CO2 concentrations protect the yield of wheat from O3 damage?

This study investigated the interacting effects of carbon dioxide and ozone concentrations on the growth and yield of spring whet (Triticum aestivum L. cv. Wembley). Plants were exposed from time of sowing to harvest to reciprocal combinations of two carbon dioxide and two ozone treatments: [CO₂] at 350 or 700 μmol mol^?1, and [O₃] at < 5 or 60 nmol mol^?1. Records of leaf emergence, leaf duration and tillering were taken throughout leaf development. At harvest, biomass, yield and partitioning were analysed. Our data showed that elevated [CO₂] fully protected against the detrimental effect of elevated [O₃] on biomass, but not yield.     

Slavery in plants: how the facultative hemi‐parasitic plant Rhamphicarpa fistulosa can completely dominate its host

The rain‐fed lowland rice weed Rhamphicarpa fistulosa (Rice Vampireweed) is a facultative root parasitic plant. Growth and reproduction of R. fistulosa benefit considerably from parasitism, but how this affects the host plant is not well established. We determined accumulation and partitioning of rice–parasite biomass in two pot experiments. First, rice (cv. IR64) was grown under eight R. fistulosa densities (15–1000 seeds per pot) with two sampling times. Next, 2 parasite densities (6 and 13 plants per pot) were combined with 9 destructive samplings. Infection increased host root: shoot ratios and decreased host plant height, leaf area and tiller number. Reductions in light interception were followed by reductions in light use efficiency, causing 22–71% losses in host plant biomass and 78–100% losses in host kernel production. Parasitism eventually caused a complete standstill of host plant growth, while the parasite managed to gradually increase its share in total host plant–parasite biomass up to 50–82%. This implies that ultimately the host plant was producing solely for the sake of the parasite. Due to its facultative nature, R. fistulosa may incorrectly be perceived as relatively harmless. Upon infection this Rice Vampireweed, however, turns into a genuine slave master, whereby it completely dominates its host.     

Root growth and plant biomass in <Emphasis Type="Italic">Lolium perenne</Emphasis> exploring a nutrient-rich patch in soil

We investigated soil exploration by roots and plant growth in a heterogeneous environment to determine whether roots can selectively explore a nutrient-rich patch, and how nutrient heterogeneity affects biomass allocation and total biomass before a patch is reached. Lolium perenne L. plants were grown in a factorial experiment with combinations of fertilization (heterogeneous and homogeneous) and day of harvest (14, 28, 42, or 56 days after transplanting). The plant in the heterogeneous treatment was smaller in its mean total biomass, and allocated more biomass to roots. The distributions of root length and root biomass in the heterogeneous treatment did not favor the nutrient-rich patch, and did not correspond to the patchy distribution of inorganic nitrogen. Specific root length (length/biomass) was higher and root elongation was more extensive both laterally and vertically in the heterogeneous treatment. These characteristics may enable plants to acquire nutrients efficiently and increase the probability of encountering nutrient-rich patches in a heterogeneous soil. However, heterogeneity of soil nutrients would hold back plant growth before a patch was reached. Therefore, although no significant selective root placement in the nutrient-rich patch was observed, plant growth before reaching nutrient-rich patches differed between heterogeneous and homogeneous environments.     

Fatty acid content of the dorsal muscle—an indicator of fat quality in freshwater fish

In 56 samples of freshwater fish, most were low in fat, ≤ 5% of dry weight (D.W.), and the sum of all fatty acids (ΣFA) was about 2% of D.W. Trout, whitefish, and grayling had the highest content of the long-chained FA. of ω3 type, EPA and DHA (1·7–2·6% of D.W.). Two large, low-fat pikes with ΣFA of about12–3% of D.W. and a medium-fat whitefish had the highest ω3/ω6 ratios, 8–9, whereas the fattiest fishes, eels from two lakes and the Baltic (ΣFA =17–26% of D.W.) had lower ω3/ω6 ratios, 1·1–1·8 (ω3 and ω6 FA are two important series of FA). The results indicate that ΣA controls the content of saturated FA (SAFA) and monounsaturated FA (MUFA), whereas the polyunsaturated FA (PUFA) was independent of ΣFA after a break point of about 10%ΣFA of D.W. The P/S ratio (PUFA/SAFA) and the PUFA/ΣFA ratio decreased with increased ΣFA, whereas the ω3/ω6 ratio showed no clear correlation to ΣFA. The difference in fatty acid patterns lay between low-fat and high-fat fishes, rather than between marine and freshwater fishes. The variation, both within and between species of the separate FA is small in fish with similar ΣFA content. Also, low-fat and medium-fat fishes tend to be more dietarily favourable than high-fat fishes, when considering the latest criteria for high nutritional value to humans. Abbreviations used in the text: FA, fatty acids; ΣFA, sum of all FA; AA, arachidonic acid (20 : 4ω6); EPA, eicosapentaenoic acid (20 : 5ω3); DHA, docosahexaenoic acid (22 : 6ω3); SAFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; D.W., dry weight; F.W. fresh weight; CV, coefficient of variation; ω3 FA, series of PUFA with the first double bond located at carbon number 3; ω6 FA, series of PUFA with the first double bond located at carbon number 6. The fatty acids are described by three numbers, x:ywz, where x=number of carbon atoms, y=number of double bonds, and z=position of the first double bond counted from the methyl end of the molecule.     

C-isotope composition of CO2 respired by shoots and roots: fractionation during dark respiration?

The CO₂ respired by leaves is ¹³C-enriched relative to leaf biomass and putative respiratory substrates (Ghashghaie et al., Phytochemistry Reviews 2, 145–161, 2003), but how this relates to the ¹³C content of root, or whole plant respiratory CO₂ is unknown. The C isotope composition of respiratory CO₂ (δ_R) from shoots and roots of sunflower (Helianthus annuus L.), alfalfa (Medicago sativa L.), and perennial ryegrass (Lolium perenne L.) growing in a range of conditions was analysed. In all instances plants were grown in controlled environments with CO₂ of constant concentration and δ¹³C. Respiration of roots and shoots of individual plants was measured with an open CO₂ exchange system interfaced with a mass spectrometer. Respiratory CO₂ from shoots was always ¹³C-enriched relative to that of roots. Conversely, shoot biomass was always ¹³C-depleted relative to root biomass. The δ-difference between shoot and root respiratory CO₂ was variable, and negatively correlated with the δ-difference between shoot and root biomass (r² = 0.52, P = 0.023), suggesting isotope effects during biosynthesis. ¹³C discrimination in respiration (R) of shoots, roots and whole plants (e_Shoot, e_Root, e_Plant) was assessed as e = (δ_Substrate − δ_R)/(1 + δ_R/1000), where root and shoot substrate is defined as imported C, and plant substrate is total photosynthate. Estimates were obtained from C isotope balances of shoots, roots and whole plants of sunflower and alfalfa using growth and respiration data collected at intervals of 1 to 2 weeks. e_plant and e_Shoot differed significantly from zero. e_plant ranged between −0.4 and −0.9‰, whereas e_Shoot was much greater (−0.6 to −1.9‰). e_Root was not significantly different from zero. The present results help to resolve the apparent conflict between leaf- and ecosystem-level ¹³C discrimination in respiration.     

Interactive effects of mechanical stress,sand burial and defoliation on growth and mechanical properties in Cynanchum komarovii

In drylands, wind, sand burial and grazing are three important factors affecting growth and mechanical properties of plants, but their interactive effects have not yet been investigated. Plants of the semi‐shrub Cynanchum komarovii, common in semi‐arid parts of NE Asia, were subjected to brushing, burial and defoliation. We measured biomass allocation and relative increment rates of dry mass (RGR_m), height (RGR_h) and basal diameter (RGR_d). We also measured the stem mechanical properties, Young’s modulus (E), second moment of area (I), flexural stiffness (EI) and breaking stress (σ_b), and scaled these traits to the whole‐plant level to determine the maximum lateral force (F_lateral) and the buckling safety factor (BSF). Brushing increased RGR_m; neither burial nor defoliation independently affected RGR_m, but together they reduced it. Among buried plants, brushing positively affected stem rigidity and strength through increasing RGR_d, E, I and EI, and at whole plant level this resulted in a larger BSF and F_lateral. However, among unburied plants this pattern was not observed. Our results thus show that effects of mechanical stress and grazing on plants can be strongly modified by burial, and these interactions should be taken into account when considering adaptive significance of plant mechanical traits in drylands.     

Effects of irradiance on growth,photosynthetic characteristics,and artemisinin content of <Emphasis Type="Italic">Artemisia annua</Emphasis> L.

With an increase in growth irradiance (from 15 to 100 % of full sunlight, I₁₅ to I₁₀₀), the maximum net photosynthetic rate (P _max), compensation (CI) and saturation irradiances of A. annua increased. At full sunlight, A. annua had a high capacity of photosynthesis, while at low irradiance it maintained a relatively high P _max with a low CI. The height and diameter growth, total and leaf biomass, and artemisinin content of A. annua decreased with the decrease in irradiance, which might be connected with lower photosynthesis at lower than at higher irradiance. Irradiances changed biomass allocations of A. annua. The leaf/total mass ratio of A. annua increased with decreasing irradiance, but the root/total mass ratio and root/above-ground mass generally increased with increasing irradiance. Thus A. annua can grow in both weak and full sunlight. However, high yield of biomass and artemisinin require cultivation in an open habitat with adequate sunshine.     

Growth enhancement of soybean (Glycine max) upon exclusion of UV-B and UV-B/A components of solar radiation: characterization of photosynthetic parameters in leaves

Exclusion of UV (280–380 nm) radiation from the solar spectrum can be an important tool to assess the impact of ambient UV radiation on plant growth and performance of crop plants. The effect of exclusion of UV-B and UV-A from solar radiation on the growth and photosynthetic components in soybean (Glycine max) leaves were investigated. Exclusion of solar UV-B and UV-B/A radiation, enhanced the fresh weight, dry weight, leaf area as well as induced a dramatic increase in plant height, which reflected a net increase in biomass. Dry weight increase per unit leaf area was quite significant upon both UV-B and UV-B/A exclusion from the solar spectrum. However, no changes in chlorophyll a and b contents were observed by exclusion of solar UV radiation but the content of carotenoids was significantly (34–46%) lowered. Analysis of chlorophyll (Chl) fluorescence transient parameters of leaf segments suggested no change in the F _v/F _m value due to UV-B or UV-B/A exclusion. Only a small reduction in photo-oxidized signal I (P700⁺)/unit Chl was noted. Interestingly the total soluble protein content per unit leaf area increased by 18% in UV-B/A and 40% in UV-B excluded samples, suggesting a unique upregulation of biosynthesis and accumulation of biomass. Solar UV radiation thus seems to primarily affect the photomorphogenic regulatory system that leads to an enhanced growth of leaves and an enhanced rate of net photosynthesis in soybean, a crop plant of economic importance. The presence of ultra-violet components in sunlight seems to arrest carbon sequestration in plants. An erratum to this article can be found at     

An AGAMOUS intron‐driven cytotoxin leads to flowerless tobacco and produces no detrimental effects on vegetative growth of either tobacco or poplar

Flowerless trait is highly desirable for poplar because it can prevent pollen‐ and seed‐mediated transgene flow. We have isolated the second intron of PTAG2, an AGAMOUS (AG) orthologue from Populus trichocarpa. By fusing this intron sequence to a minimal 35S promoter sequence, we created two artificial promoters, fPTAG2I (forward orientation of the PTAG2 intron sequence) and rPTAG2I (reverse orientation of the PTAG2 intron sequence). In tobacco, expression of the β‐glucuronidase gene (uidA) demonstrates that the fPTAG2I promoter is non‐floral‐specific, while the rPTAG2I promoter is active in floral buds but with no detectable vegetative activity. Under glasshouse conditions, transgenic tobacco plants expressing the Diphtheria toxin A (DT‐A) gene driven by the rPTAG2I promoter produced three floral ablation phenotypes: flowerless, neuter (stamenless and carpel‐less) and carpel‐less. Further, the vegetative growth of these transgenic lines was similar to that of the wild‐type plants. In field trials during 2014 and 2015, the flowerless transgenic tobacco stably maintained its flowerless phenotype, and also produced more shoot and root biomass when compared to wild‐type plants. In poplar, the rPTAG2I::GUS gene exhibited no detectable activity in vegetative organs. Under field conditions over two growing seasons (2014 to the end of 2015), vegetative growth of the rPTAG2I::DT‐A transgenic poplar plants was similar to that of the wild‐type plants. Our results demonstrate that the rPTAG2I artificial promoter has no detectable activities in vegetative tissues and organs, and the rPTAG2I::DT‐A gene may be useful for producing flowerless poplar that retains normal vegetative growth.     

Wall yield threshold and effective turgor in growing bean leaves

The rate of cell enlargement depends on cell-wall extensibility (m) and on the amount of turgor pressure (P) which exceeds the wall yield threshold (Y). The difference (P-Y) is the growth-effective turgor (P _e). Values of P, Y and P _ehave been measured in growing bean (Phaseolus vulgaris L.) leaves with an isopiestic psychrometer, using the stress-relaxation method to derive Y. When rapid leaf growth is initiated by light, P, Y and P _eall decrease. Thereafter, while the growth rate declines in maturing leaves, Y continues to decrease and P _eactually increases. These data confirm earlier results indicating that the changes in light-stimulated leaf growth rate are primarily controlled by changes in m, and not by changes in P _e. Seedlings incubated at 100% relative humidity have increased P, but this treatment does not increase growth rate. In some cases Y changes in parallel with P, so that P _eremains unchanged. These data point out the importance of determining P _e, rather than just P, when relating cell turgor to the growth rate.Abbreviations and symbols FC fusicoccin - m wall extensibility - P turgor pressure - P _e effective turgor - RH relative humidity - Y yield threshold - _w water potential - _s osmotic potential     

土壤灭菌处理对入侵植物南美蟛蜞菊及其伴生种生长的影响

该研究以温室盆栽法对南美蟛蜞菊重度入侵土壤进行高温高压湿热灭菌、添加杀真菌剂灭菌和添加杀细菌剂灭菌的处理后,将三种植株定植96 d后测定各生理指标参数,研究重度入侵土壤中各微生物类群对南美蟛蜞菊及其伴生种金腰箭和狗肝菜生长的影响。结果表明:在杀真菌、杀细菌以及高温高压湿热灭菌和未处理的南美蟛蜞菊重度入侵土壤中,三种植物生长情况均存在较大差异。在高温高压湿热灭菌土壤中南美蟛蜞菊的生长受到显著抑制,与未处理土壤中的生长情况相比,株高降低了17.59%,叶片数降低了38.10%,生物量降低了56.00%,电子传递速率变化不明显。在杀真菌土壤和杀细菌土壤中金腰箭的生长也受到显著抑制,与未处理土壤中的生长情况相比较,杀真菌土壤中的金腰箭株高降低最多(为42.28%),叶片数降低了38.89%,生物量降低了16.99%,电子传递速率变化不明显;在杀细菌土壤中金腰箭株高降低了36.64%,叶片数降低最多(为38.89%),生物量降低了33.67%,电子传递速率升高了11.11%。由此可见,不含微生物的土壤对南美蟛蜞菊生长有较强的抑制作用,不含真菌和细菌的土壤对金腰箭的生长有明显抑制作用。南美蟛蜞菊重度入侵土壤不仅适合南美蟛蜞菊的生长,也适合金腰箭的生长,对狗肝菜影响不大。