Foliar nutrients explain goldspotted oak borer,Agrilus auroguttatus,adult feeding preference among four California oak species

Adults of the invasive goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), consumed foliar weight in no‐choice feeding tests of, in descending order, California black oak Quercus kelloggii Newb., Engelmann oak, Quercus engelmannii Greene, coast live oak, Quercus agrifolia Née, and canyon live oak, Quercus chrysolepis Liebm. (Fagaceae). Furthermore, significantly more foliar area was consumed of Q. kelloggii than of Q. chrysolepis. In dual‐choice feeding tests with isolated leaf disks, A. auroguttatus consumed significantly more foliar weight and area of Q. kelloggii relative to the other three oak species, and more foliar weight of Q. agrifolia than of Q. chrysolepis. In dual‐choice feeding tests with leaves on small branches, A. auroguttatus consumed more foliar weight of Q. kelloggii than of Q. engelmannii and Q. agrifolia. Thus, multiple experiments suggested that adults of A. auroguttatus preferred the foliage of Q. kelloggii over that of the other three oak species, and among the other three species they did not appear to have a strong feeding preference. Factor analysis reduced the quantities of 13 foliar nutrients into two new variables (factor 1 and factor 2). Factor 1 was weighted heavily on the quantities of nitrogen, sulfur, phosphorus, potassium, zinc, and copper, whereas factor 2 was weighted heavily on the quantities of zinc, iron, and aluminum. Factor 1 varied by oak species, with Q. kelloggii having a higher factor 1 nutrient content than the other three species. Factor 2 response was higher in Q. kelloggii, Q. agrifolia, and Q. engelmannii than in Q. chrysolepis. The collective effects of four macronutrients (nitrogen, sulfur, phosphorus, and potassium) and two micronutrients (zinc and copper) suggest that these might be the nutrients directing preferential feeding of A. auroguttatus adults on the foliage of Q. kelloggii. Leaf toughness might also play an important role in feeding preference. Female A. auroguttatus did not show an ovipositional preference among the four oak species.     

干旱荒漠区银白杨树干液流动态

应用热扩散式树干茎流计(TDP)于2012年7月1日至7月25日,在克拉玛依地区农业开发区对银白杨(Populus alba L.×P.talassica)人工林树干液流速率进行了连续测定,并对气象、土壤水分等指标进行了同步测定。结果表明:7月份的晴天银白杨树干液流速率日变化呈单峰型,阴天呈多峰型,在测量时期液流速率日平均值为0.6059 L/h;银白杨树干单位边材面积的液流速率与太阳总辐射、大气温度、水汽压差呈极显著正相关关系,与相对湿度呈负相关关系。其相关系数绝对值顺序为太阳总辐射>大气温度>水汽压差>相对湿度>风速;银白杨边材面积与胸径之间存在着显著的线性相关关系,相关系数为0.834,单位边材面积的液流速率随树干胸径的增大而减小。     

模拟酸雨对蒙古栎幼苗生长和根系伤流量的影响

选择中国北方落叶阔叶林的主要组成树种蒙古栎(Quercus mongolica Fisch.ex Ledeb.)的1年生幼苗为研究对象,设置4个酸雨酸度(重度、中度、轻度和对照)和3个降雨量(自然雨量和增、减雨量30％),以期阐明酸雨对蒙古栎幼苗形态生长、生物量和根系伤流量的影响,探讨中国北方日趋严重的酸雨是否会影响蒙古栎幼苗的生长,为酸雨区森林恢复植物的选择提供依据.研究结果显示:1)在本实验的酸雨酸度下,酸雨降雨量的增加对蒙古栎幼苗各生理生态指标均有一定的促进作用;2)酸雨酸度对蒙古栎幼苗形态和生物量的影响不显著,但酸度增加降低了幼苗的根系伤流量;3)增雨的重度酸雨处理促进了蒙古栎幼苗形态生长和生物量累积;4)两因素对蒙古栎幼苗的影响没有交互作用.说明蒙古栎对酸雨具有一定的抗性,可考虑选择为酸雨区植被构建的物种.     

光照强度对大花旋蒴苣苔叶形态和生理指标的影响

以复苏植物大花旋蒴苣苔(Boea clarkeana)为盆栽实验材料,通过梯度遮光处理,研究不同光照强度(100%、80%、60%、40%和20%透光率)和不同处理时间(30、60、90、120和150d)对大花旋蒴苣苔叶生长指标和生理指标的影响。结果表明:随着光照强度的减弱,大花旋蒴苣苔叶的各生长指标(叶片长、叶片宽、叶柄长、叶柄直径以及叶面积)呈现先增大后减小的趋势,透光率为60%时达到最大值;全光照(100%透光率)时,大花旋蒴苣苔表现出明显的外伤症状,透光率为80%和20%时,分别表现出中度伤害和轻度伤害,透光率为40%和60%时,未出现明显的外伤症状;过氧化氢酶(CAT)、超氧化物歧化酶(SOD)和过氧化物酶(POD)3种抗氧化酶活性均较低且随着光强减弱呈现先降低后升高的趋势,随着处理时间的延长呈先上升后下降的趋势,全光照时抗氧化酶的活性最大,透光率60%处理下酶活性相对较低;丙二醛(MDA)含量、脯氨酸(Pro)含量和质膜透性随着光强减弱呈先降低后升高的趋势,随着处理时间的延长显著升高;叶绿素含量随着光强减弱呈逐渐上升的趋势,随着处理时间的延长先降低后升高。分析表明,40%～60%的透光率有利于大花旋蒴苣苔的生长,强光和弱光对大花旋蒴苣苔的生长均不利。     

Aquaporins in developing rice grains

During rice grain filling, grain moisture content and weight show dynamic changes. We focused on the expression of all 33 rice aquaporins in developing grains. Only two aquaporin genes, OsPIP2;1 and OsTIP3;1, were highly expressed in the period 10–25 days after heading (DAH). High-temperature treatment from 7 to 21 DAH abolished the dynamic up-regulation of OsPIP2;1 in the period 15–20 DAH, whereas OsTIP3;1 expression was not affected. Immunohistochemical analysis revealed that OsPIP2;1 was present in the starchy endosperm, nucellar projection, nucellar epidermis, and dorsal vascular bundles, but not in the aleurone layer. OsTIP3;1 was present in the aleurone layer and starchy endosperm. Water transport activity of recombinant OsTIP3;1 was low, in contrast to the high activity of recombinant OsPIP2;1 we reported previously. Our data suggest that OsPIP2;1 and OsTIP3;1 have distinct roles in developing grains.     

Triticum monococcum lines with distinct metabolic phenotypes and phloem‐based partial resistance to the bird cherry–oat aphid Rhopalosiphum padi

Crop protection is an integral part of establishing food security, by protecting the yield potential of crops. Cereal aphids cause yield losses by direct damage and transmission of viruses. Some wild relatives of wheat show resistance to aphids but the mechanisms remain unresolved. In order to elucidate the location of the partial resistance to the bird cherry–oat aphid, Rhopalosiphum padi, in diploid wheat lines of Triticum monococcum, we conducted aphid performance studies using developmental bioassays and electrical penetration graphs, as well as metabolic profiling of partially resistant and susceptible lines. This demonstrated that the partial resistance is related to a delayed effect on the reproduction and development of R. padi. The observed partial resistance is phloem based and is shown by an increase in number of probes before the first phloem ingestion, a higher number and duration of salivation events without subsequent phloem feeding and a shorter time spent phloem feeding on plants with reduced susceptibility. Clear metabolic phenotypes separate partially resistant and susceptible lines, with the former having lower levels of the majority of primary metabolites, including total carbohydrates. A number of compounds were identified as being at different levels in the susceptible and partially resistant lines, with asparagine, octopamine and glycine betaine elevated in less susceptible lines without aphid infestation. In addition, two of those, asparagine and octopamine, as well as threonine, glutamine, succinate, trehalose, glycerol, guanosine and choline increased in response to infestation, accumulating in plant tissue localised close to aphid feeding after 24 h. There was no clear evidence of systemic plant response to aphid infestation.     

Separating water‐potential induced swelling and shrinking from measured radial stem variations reveals a cambial growth and osmotic concentration signal

The quantification of cambial growth over short time periods has been hampered by problems to discern between growth and the swelling and shrinking of a tree stem. This paper presents a model, which separates cambial growth and reversible water‐potential induced diurnal changes from simultaneously measured whole stem and xylem radial variations, from field‐measured Scots pine trees in Finland. The modelled growth, which includes osmotic concentration changes, was compared with (direct) dendrometer measurements and microcore samples. In addition, the relationship of modelled growth and dendrometer measurements to environmental factors was analysed. The results showed that the water‐potential induced changes of tree radius were successfully separated from stem growth. Daily growth predicted by the model exhibited a high correlation with the modelled daily changes of osmotic concentration in phloem, and a temperature dependency in early summer. Late‐summer growth saw higher dependency on water availability and temperature. Evaluation of the model against dendrometer measurements showed that the latter masked a true environmental signal in stem growth due to water‐potential induced changes. The model provides better understanding of radial growth physiology and offers potential to examine growth dynamics and changes due to osmotic concentration, and how the environment affects growth.     

Stomatal acclimation to vapour pressure deficit doubles transpiration of small tree seedlings with warming

Future climate change is expected to increase temperature (T) and atmospheric vapour pressure deficit (VPD) in many regions, but the effect of persistent warming on plant stomatal behaviour is highly uncertain. We investigated the effect of experimental warming of 1.9–5.1 °C and increased VPD of 0.5–1.3 kPa on transpiration and stomatal conductance (g_s) of tree seedlings in the temperate forest understory (Duke Forest, North Carolina, USA). We observed peaked responses of transpiration to VPD in all seedlings, and the optimum VPD for transpiration (D_opt) shifted proportionally with increasing chamber VPD. Warming increased mean water use of Carya by 140% and Quercus by 150%, but had no significant effect on water use of Acer. Increased water use of ring‐porous species was attributed to (1) higher air T and (2) stomatal acclimation to VPD resulting in higher g_s and more sensitive stomata, and thereby less efficient water use. Stomatal acclimation maintained homeostasis of leaf T and carbon gain despite increased VPD, revealing that short‐term stomatal responses to VPD may not be representative of long‐term exposure. Acclimation responses differ from expectations of decreasing g_s with increasing VPD and may necessitate revision of current models based on this assumption.     

Effects of groundwater salinity on the characteristics of leaf photosynthesis and stem sap flow in Tamarix chinensis

AimsThe objective of this study was to investigate the change pattern of leaves photosynthesis and stem sap flow of Tamarix chinensisin under different groundwater salinity, which can be served as a theoretical basis and technical reference for cultivation and management of T. chinensis in shallow groundwater table around Yellow River Delta.MethodsThree-year-old T. chinensis, one of the dominated species in Yellow River Delta, was selected. Plants were treated by four different salinity concentrations of groundwater—fresh water (0 g∙L^-1), brackish water (3.0 g∙L^-1), saline water (8.0 g∙L^-1), and salt water (20.0 g∙L^-1) under 1.2 m groundwater level. Light response of photosynthesis and the diurnal courses of leaf transpiration rate, stem sap flux velocity and environment factors under different groundwater salinity were determined via LI-6400XT portable photosynthesis system and a Dynamax packaged stem sap flow gauge based on stem-heat balance method, respectively.Important findings The result showed that groundwater salinity had a significant impact on photosynthesis efficiency and water consumption capacity of T. chinensis by influencing the soil salt. The net photosynthetic rate (P_n), maximum P_n, transpiration rate, stomatal conductance, apparent quantum yield and dark respiration rate increased first and then decreased with increasing groundwater salinity, while the water use efficiency (WUE) continuously decreased. The mean P_n under fresh water, brackish water and salt water decreased by 44.1%, 15.1% and 62.6%, respectively, compared with that under saline water (25.90 µmol∙m^-2∙s^-1). The mean WUE under brackish water, saline water and salt water decreased by 25.0%, 29.2% and 41.7%, respectively, compared with that under fresh water (2.40 µmol∙mmol^-1). With the increase of groundwater salinity from brackish water to salt water, light saturation point of T. chinensisdecreased while the light compensation point increased, which lead to the decrease of light ecological amplitude and light use efficiency. Fresh water and brackish water treatment helped T. chinensis to use low or high level light, which could significantly improve the utilization rate of light energy. The decrease in P_n of T. chinensis was mainly due to non-stomatal limitation under treatment from saline water to fresh water, while the decrease in P_n of T. chinensis was due to stomatal limitation from saline water to salt water. With increasing groundwater salinity, stem sap flux velocity of T. chinensis increased firstly and then decreased, reached the maximum value under saline water. The mean stem sap flux velocity under fresh water, brackish water and salt water decreased by 61.8%, 13.1% and 41.9%, respectively, compared with that under saline water (16.96 g·h^-1). Tamarix chinensis had higher photosynthetic productivity under saline water treatment, and could attained high WUE under severe water deprivation by transpiration, which was suitable for the growth of T. chinensis.     

尾巨桉液流特征分析

目前尾巨桉( Eucalyptus urophylla × E. grandis)在南部大面积种植,尤其是在广西,其水分利用效率对森林可持续发展和水资源管理的影响越来越受到关注,因此了解其水分利用特征具有一定的意义。该文通过Granier热扩散探针法(TDP)对广西黄冕国有林场4~5年生尾巨桉人工林液流密度(SFD)的年变化规律、不同个体变化及其与环境因子的关系进行了研究。结果表明：尾巨桉年平均日液流密度为830.1 L.m-2.d-1;从尾巨桉日液流密度的年变化来看,最大值不超过2000 L.m-2.d-1,与相似研究比较,该研究得到的结果偏低。不同直径尾巨桉SFD具有相似的变化趋势,胸径相近其液流密度也大致相同,但胸径相差很大时,其液流密度相差也大,相差最大可达1300 L.m-2.d-1,这主要与不同生长状况的植物根系从土壤吸收水分能力不同有关。相关研究表明光合有效辐射和水汽压亏缺是树木冠层蒸腾的主要动力,该研究也发现树干液流密度与水汽压亏缺( VPD)、光合有效辐射( PAR)在年变化上有很好的同步性,主要表现出夏秋季节较高、春冬季节较低的现象。 SFD与PAR的关系比较显著,与VPD、空气温度( AT)、土壤温度( ST)有一定的关系,但与空气相对湿度( RH)和土壤湿度( SM)没有呈现规律。环境因子和植物生物学特征是树干液流密度主要的影响因素,进一步探讨尾巨桉如何响应这些因子的变化显得尤为重要。