城市观赏树种桂花的光合特性初步研究

用LI-COR6400 便携式光合作用测定仪系统研究园林观赏树种桂花的光合特性,结果表明:①桂花叶片的光补偿点为21靘ol photons m-2·s-1,最大净光合速率为3.8靘ol·m-2·s-1,光饱和点为1 748靘ol photons m-2·s-1。②桂花叶片的净光合速率(Photo)日变化为单峰曲线,与光合有效辐射(PAR)的日变化走势一致。③相关分析表明:净光合速率与气孔导度(Cond)、蒸腾速率(Trmmol)、光合有效辐射成显著的正相关,而与饱和蒸汽压差(Vpdl)成显著的负相关;主成分分析表明:光照、温度是光合作用的主导因子,胞间CO2浓度(Ci)、叶面的相对湿度(Rhs)对净光合速率影响也较大;逐步线形回归表明:净光合速率主要受到叶片温度(Tleaf)和胞间CO2浓度的影响。     

果桑的光合特性

叶片是果树光合作用的主要器官.在云南省草坝农场果桑试验示范园对果桑的光合作用进行了测定.结果表明:果桑净光合速率、蒸腾速率、气孔导度的日变化均呈双峰曲线,且在1 d内的变化趋势类似;光合有效辐射以及温度的走势也极为相似;气孔导度随光合有效辐射的增加和随胞间CO2浓度的增加而减少;果桑的光饱和点为1 841.1μmol.m-2.s-1,光补偿点为34.8μmol.m-2.s-1.     

桉树无性系苗期光合作用特性研究

对6个桉树人工林高产无性系的苗期光合作用特性进行了测定,结果表明:尾叶桉净光合速率与光强呈显著的二次曲线相关关系,光响应的饱和点为1967 7μmol·m-2·s-1。桉树无性系具较高的净光合速率与蒸腾速率,不同无性系各项光合生理生态指标差异显著,尾×巨桉、尾×细桉等生长量较好的无性系较尾×赤桉和尾叶桉无性系的水分利用效率更高,光合能力更强。净光合速率、蒸腾速率及气孔导度三者日变化进程较为相似,而胞间CO2浓度的日变化趋势则与净光合速率相反。净光合速率、气孔导度与蒸腾作用与树高、胸径、单株材积等生长指标存在一定程度的正相关关系,可应用于优良无性系的早期选择。     

美洲黑杨无性系苗期光合生理特性研究

研究了9个美洲黑杨无性系的光合生理特性,为优良新无性系的选育提供参考。采用LI-6400便携式光合作用测定系统测定美洲黑杨的光合作用日变化及其光响应曲线,利用非直角双曲线Farquhar模型、二次曲线及直线方式拟合光响应曲线,分析比较光响应特征参数及影响净光合速率因子。结果表明:各无性系的净光合速率均具有明显的日变化规律,tn01-78、tn01-38、tn04-n52呈双峰曲线现象,2个峰值出现的时间在11:00和14:00左右,其余呈单峰曲线,净光合速率最大值出现在12:00左右;不同无性系最大净光合速率、暗呼吸速率、表观量子效率、光饱和点和光补偿点的大小范围分别为20.50~31.42μmol·m-2s-1、1.67~3.19μmol·m-2s-1、0.055~0.279μmol·μmol-1、950.83~1 360.83μmol·m-2s-1和29.03~55.20μmol·m-2s-1;净光合速率(Pn)变化与气孔导度Gs、水压亏缺Vpdl、空气温度Tair和光合有效辐射VPAR呈正相关,与胞间CO2浓度Ci和大气相对湿度(HR)呈负相关;净光合速率与影响因子的相关程度依次为气孔导度>光合有效辐射>胞间CO2浓度>大气相对湿度>空气温度>水压亏缺。     

杉木人工林针叶光合与蒸腾作用的时空特征

对3个林分(密度A1 667株·hm-2;B3 233株·hm-2;C9 767株·hm-2)的测定和分析表明,树冠不同部位的同龄叶的光补偿点、光饱和点及其最大光合速率不同;树冠同一层内,成熟针叶光合速率依当年生叶、1 a生叶、2 a生叶递减.强光下,中层叶的蒸腾速率明显小于上层叶.弱光下,中层和下层叶具有较高的蒸腾速率,几乎等于甚至超过上层叶.一般而言,杉木针叶光合作用的光饱和点为1 000～1 900 μmol·m-2s-1,光补偿点很低,大致在4.780 ～30.114 μmol·m-2s-1范围.同一枝条不同部位不同年龄针叶光合和蒸腾的能力差异明显.枝条后部针叶净光合速率和蒸腾速率明显小于处于枝中、前部的同龄叶,却明显具有较高的量子利用效率或对弱光(以散射光为主)的利用效率,分别为当年生叶0.006 60 μmolCO2·μmol-1PAR;1 a生叶0.017 94 μmolCO2·μmol-1PAR;2 a生叶0.012 97 μmol CO2·μmol-1PAR. 针叶最大光合速率可达13.335 μmolCO2·m-2s-1 .同一枝条不同部位的杉木针叶的蒸腾效率变化于0.003 5 ～0.007 gCO2·g-1H2O,越靠近枝条后部,蒸腾效率越低.一般而言,阳生叶的光合能力是阴生叶的2～4倍.生长季中当年生针叶光合和蒸腾速率的日变化均有2个峰值,中部和下部当年生叶的变化幅度小于上部针叶.辐射强度、空气湿度或者叶片周围空气的水汽压,是决定叶片气孔导度、光合与蒸腾速率的主要环境因子.呼吸作用白天明显高于夜间,多呈中午单峰型;日变化规律主要受温度、叶片周围空气的水汽压大小控制.蒸腾和呼吸呈紧密线性负相关.3个林分中,无论是2 a生叶,1 a生叶或当年生叶,光合强度均是密度小的最大,密度大的最小.密度越大,叶平均N素含量越低,光饱和点越低,而光补偿点越高,偏向于利用较弱的光,生长也较弱.     

西藏林芝云杉针叶净光合速率对环境因子的响应

使用便携式光合系统仪Li 6200测定了西藏林芝云杉净光合速率的日变化及其对环境因子如量子辐射、相对湿度和CO2浓度的响应。研究结果表明:林芝云杉的净光合速率在11:00点左右达到最大值,然后逐渐下降,到19:00点左右净光合速率降到0以下,转入暗呼吸。林芝云杉树冠上层的针叶由于受光充分,净光合速率较下层针叶大;阴生叶与阳生叶的净光合速率,上层差别不大,下层以阴生叶为大。在气温20℃左右、相对湿度70%±5%、CO2浓度为305mg·kg-1条件下,林芝云杉的光补偿点约为107 5μmol·m-2·s-1,光饱和点约为770μmol·m-2·s-1;在光强800μmol·m-2·s-1、气温20℃左右、相对湿度70%±5%条件下,林芝云杉的CO2补偿点约为157 2mg·kg-1,CO2饱和点约为3811 33mg·kg-1。     

南召宝天曼生境下山茱萸光合生理生态特性研究

在完全自然生长不离体的情况下,利用Li-6400测定南召宝天曼生境下山茱萸7月份的光合生理生态指标.结果表明;山茱萸净光合速率日变化呈双峰曲线,具有光合"午休"现象且由非气孔限制因素所致;山茱萸净光合速率与叶片气孔导度、胞间C02浓度、气孔限制值呈线性相关,与光合有效辐射呈二次抛物线型相关,与其它生理生态因子之间没有直接的显著相关,但逐步回归多元统计分析显示利用叶片气孔导度和叶片温度二因子预测山茱萸净光合速率精度较高;在叶温28C和空气CO2浓度360μmol·tool-1条件下,山茱萸净光合速率随光合有效辐射的增强而提高,光补偿点和光饱和点分别为25 μmol·m-2·s-1、1000μmol·m-2·s1,在此条件下,净光合速率与蒸腾速率和叶片气孔导度没有显著的相关关系．但与胞间CO2浓度呈二次抛物线璎显著相关;在叶温28C和光合有效辐射900 μmol·m-2·s-1条件下,净光合速率随着CO2浓度的增加而提高,CO2补偿点和CO2饱和点分别为100μmol·mol-1、1400μmol·mol-1此条件下净光合速率与蒸腾速率和胞间CO2浓度均星对数曲线显著正相关.     

不同光环境下水曲柳幼树光合指标的生理反应

应用Li-640002B型光合仪对生长在不同光环境下的水曲柳幼树的光合特性进行了测定。统计分析结果表明,幼树对低光环境具有较强的适应能力,能够在0.512μmol·m-2·s-1的条件下正常生活。幼树光合速率最高可达13.0μmol·m-2·s-1,光饱和点(LSP)1000μmol·m-2·s-1左右,适生光环境为800～1000μmol·m-2·s-1。     

红花木莲苗期光合特性研究

通过对濒危植物红花木莲苗期光合生理特性的研究。结果表明,红花木莲苗期的光合日进程呈明显的双峰曲线,峰值分别出现在上午9 00和下午15 00左右。在中午13 00左右出现光合作用明显下降的光午休现象。光午休现象的出现可能与当时气温的升高和湿度饱和差的增加有关,因此使叶保卫细胞失水增多导致气孔导度减小以致引起光合速率下降。此外,也可能与二氧化碳羧化酶的活性降低有关。分析红花木莲苗期的水分利用效率,发现苗木的水分利用效率与其光合速率的日变化趋势有较大的一致性。对红花木莲的叶片的光响应曲线进行分析,得到红花木莲苗期的光补偿点和光饱和点。其光饱和点和光补偿点分别为1200～1300μmolCO2·m-2·s-1和23 487μmol·m-2·s-1。     

两个金银花品种光合作用日变化的比较

为了了解‘济草堂1号’和‘九丰1号’金银花光合作用日变化的差异,采用Li-6400便携式光合作用测定仪对10月和11月2个品种的光合特性日变化进行观测。结果表明:‘济草堂1号’的净光合速率均值为7.84μmol·m-2s-1,大于‘九丰1号’(7.66μmol·m-2s-1)。2个品种金银花的气孔导度、胞间CO2浓度、蒸腾速率、气孔限制值和水分利用率均存在一定差异,其中‘济草堂1号’金银花平均的气孔导度为0.22mol·m-2s-1、胞间CO2浓度为282.915μmol·mmol-1、蒸腾速率为3.42mmol·m-2s-1、气孔限制值为0.295%、水分利用率为2.265μmol·mmol-1,‘九丰1号’金银花平均的气孔导度为0.205mmol·m-2s-1、胞间CO2浓度为275.685μmol·mmol-1、蒸腾速率为3.53mmol·m-2s-1、气孔限制值为0.315%、水分利用率为2.165μmol·mmol-1。2个品种金银花净光合效率日变化均为双峰,其它光合特征参数日变化与之呈相对应的规律。     

Armillaria ostoyae in managed coniferous forests in Kastamonu in Turkey

Although several Armillaria species have been reported in Turkey, there is little information about their ecology in Turkish forests. In this study, we investigated five forest stands, approximately 5–74 ha in size, in Kastamonu province in the Black Sea Region of Turkey for the presence of Armillaria species in stumps and logs. The stands were mixed Abies nordmanniana ssp. bornmülleriana and Pinus sylvestris forests managed using a selective cuttings system; the proportion of fir in the total number of stems and stumps ranged from 36 to 98%. Based on sequence analysis of the internal transcribed spacer and intergenic spacer regions of the rDNA, all rhizomorphs sampled from the stumps and logs were of Armillaria ostoyae. The size of the genets was estimated with random amplified microsatellites analysis of the isolates and ranged from single stumps to approximately 450 m². One to seven genets were found in each stand. These results indicate that the genets had arisen from spores and vegetative spread was limited on most sites.     

上海中央公园特大银杏树白蚁防治探讨

通过对上海松江中央公园内65株特大银杏树白蚁为害情况的调查,发现该公园银杏受害率为100%,其中存在活白蚁的银杏占总量的56.9%,采用毒土处理、粉剂疗法、建立白蚁监测点等措施,经过两次灭杀,活白蚁的灭杀率达到92.3%和93.3%,从而使存在活白蚁银杏树的比例从56.9%下降到2.7%,白蚁发生情况明显降低。       

我国食品中农药残留研究进展

随着人们安全健康意识提高,食品中农药残留问题更加受到重视,本文综述了样品预处理研究进展及农药残留快速检测技术研究进展,并简单分析介绍各种方法的优缺点。     

建平半干旱地区石质山地造林技术研究

研究了不同植物在石质山地的造林成活率、土壤化学性质随造林年限的变化和造林措施对土壤化学性质和植物胸径、树高年净生长量的影响。结果表明：不同植物在石质山地的成活率在21%～85%之间,其中白榆和沙打旺的成活率分别为81%和85%,而小叶杨、刺槐、栾树的成活率均在70%左右;植被能明显提高石质山地不同土层的有机质、全N、P2O5含量,但提高程度随土层深度、养分种类和造林年限的不同而不同;在同一土层,生物复合肥料、菌剂和保水剂均显著提高土壤有机质含量（p〈0.01）并显著降低土壤P2O5含量（p〈0.01）;只有保水剂可引起土壤全K含量的明显升高;生物复合肥料、菌剂和保水剂均显著提高白榆、小叶杨、刺槐、栾树树高和胸径的年净生长量,但保水剂的提高程度最高。     

植物DNA甲基化研究进展

植物经常暴露在各种生物和非生物的胁迫之下,这些胁迫会影响植物的生长发育和繁殖并最终导致植物死亡。为了抵御不利的环境条件,植物已经进化出复杂而精细的网络来感知胁迫并激活防御系统。为此,植物激活许多信号转导通路,这些信号转导通路可以改变一些胁迫响应基因的表达,从而引起植物形态、生理和生化的改变以适应逆境。DNA胞嘧啶甲基化是高等真核生物的主要表观遗传机制之一,在维持基因组稳定性和调节基因表达方面起着关键作用。表观遗传变异比遗传变异更为灵活。一旦环境条件发生变化,为了适应新的环境植物都会发生表观遗传的改变。许多研究表明DNA甲基化参与植物的发育和应激反应。基于相关研究对DNA甲基化进行了综述,对植物逆境胁迫有重要意义。     

木材碳封存研究进展

碳封存可以分工业封存和生物封存, 工业封存包括地质封存、海洋封存、矿石碳化以及工业循环利用, 这些方法能快速回收CO₂, 但工艺流程技术复杂, 成本较高。木材碳封存是生物碳封存的一种类型, 树木光合作用吸收的碳主要存贮在木材中。运用木材密度、微密度等检测仪器, 通过确定木材密度变化, 结合其含碳率来计量木材的碳封存过程以及封存过程中碳的分配格局, 同时研究其与环境因子的相关性, 可以为研究森林的碳吸收动态提供便捷的方法和科学的依据。     

Tree regeneration in patch cutting in Norway spruce stands in northern Finland

The study focused on the success of regeneration on patch cuts in spruce-dominated stands in terms of stocking and tree height. It was based on an experiment in the Kainuu region in northern Finland. The experimental design included 8 stands with 58 clearcut patches of variable size (0.09–0.37?ha), on which either natural regeneration without site preparation or site preparation and planting of Scots pine was applied. A regeneration survey was conducted 13–15 growing seasons after treatments. Patches without site preparation had been restocked quite well from natural seed sources. The average number of trees was about 11,000?ha^?1, of which 1700?ha^?1 crop trees. With site preparation and planting, the stocking levels were also very high, 25,000 and 2100?ha^?1, respectively. One hundred percent of the planted patches and 75% of the naturally regenerated patches had an acceptable density. Restocking was equally good across the range of patch sizes. Tree growth had been somewhat slower in the smallest patches than in the largest ones in the range. Natural regeneration was capable of yielding good regeneration results in most patches, especially when site preparation was applied. Stocking levels and height development were higher yet in the planted patches.     

Natural regeneration in patch clear-cutting in Picea abies stands in Southern Finland

Abstract

The success of natural regeneration on patch clear-cuts in Norway spruce stands in Southern Finland was examined in terms of stocking and tree height. The experiment was established in mature spruce stands in the submesic Myrtillus (MT) site type. In each of the eight study sites, three plots were treated with clear-cutting and planting, clear-cutting with partial tree retention and planting, and patch clear-cutting without site preparation, respectively. In three of the study sites, one plot with patch clear-cutting and site preparation was established. Each plot was 1 ha, out of which three patches of 40×40 m were clear-cut in the patch treatments. 10–11 years after cutting, the patches had on average 1316 crop trees ha^–1, of which 91% were spruces. Some 27% of the stands were up to the target stocking level (≥1600 ha^?1), and 36% were at least satisfactory (≥1300 ha^?1). Site preparation did not yield greater stocking levels on patches, but that result is ambiguous due to a difference in initial stocking. The average spruce tree height in the patches (0.76 m) was much smaller than in the case of clear-cutting and planting (2.42 m). In conclusion, the patches had been restocked tolerably well with spruce and birch for practical purposes during the 10- to 11-year period, but the regeneration process had been very slow compared to clear-cutting and planting.     

Changes in micropores in dry wood with elapsed time in the environment

To investigate the changes in microstructures of wood with elapsed time in the environment, CO₂ adsorption onto dry wood was measured at ice-water temperature (273 K) for samples aged from 0.1 years to over 1000 years. The micropore size distribution was obtained using the Horvath-Kawazoe method. Micropores smaller than 0.6 nm in wood decreased in number with elapsed time in the environment, and a negative correlation was found between cumulative pore volume for pores smaller than 0.6 nm and elapsed time in the environment. Cumulative pore volume in the 1000-year sample was almost half of that in the 0.1- year sample. Micropores smaller than 0.6 nm in wood with a few decades or more of elapsed time increased in number after rewetting and drying. Consequently, microstructures of wood with longer time elapsed in the environment were considered to be more stable, because of longer-term thermal motion and possibly more repeated moisture adsorption and desorption and/or temperature variation in the environment.