油蒿叶片氮分配对其最大净光合速率季节变异的影响

植物最大净光合速率的季节变异性及其氮调控机制是近年来植物生理生态领域研究热点,对荒漠植物光合最大净光合速率季节动态及其叶氮影响,特别是叶氮分配对最大净光合速率调控机制的了解仍非常有限。2018年5-10月在宁夏盐池毛乌素沙地,对当地主要建群种油蒿(Artemisia ordosica)进行生长季原位观测,测定其叶光合光响应曲线(A-PAR)、CO₂响应曲线(A-Ci)和叶氮含量,结合环境观测数据,分析A-PAR关键参数最大净光合速率(A_max)的季节变异和叶片氮分配相关参数对A_max的调控。结果表明,油蒿叶片A_max在生长期季节变异系数(Cv)为14%,在完全展叶中期,光合氮利用效率(PNUE)有最大值11.82 μmolCO₂ gN^-1 s^-1,此时叶片氮素在光合系统中的分配比例最大,A_max有最大值29.48 μmol CO₂ m^-2s^-1,油蒿光合能力较强。在完全展叶末期,油蒿叶片氮在光合系统中的分配比例(P_p)有最小值0.21,此时叶氮分配更倾向于非光合系统,A_max较小,光合能力较弱,有利于油蒿延长叶片寿命。A_max与单位干重叶片氮含量(N_mass)、氮在捕光系统中分配比例(P_L)、氮在生物力能系统中分配比例(P_b)正相关(P<0.05),其中,P_L对A_max产生了最大的直接正向影响,氮在羧化系统中分配比例(P_c)主要通过P_b对A_max的产生了间接的正向影响,P_b对A_max季节动态的解释度最大(R²=0.49,P<0.01)。A_max与比叶重(LMA)负相关(P<0.05),即当有较高LMA时油蒿具有较低的光合速率,此时叶片光合能力较弱,叶片机械韧性较强。不同物候时期,油蒿叶片氮素分配的变化及叶片光合能力与结构性状之间的权衡关系,标志着荒漠植物对其生境的适应性调节。研究结果不但可提高荒漠灌木油蒿生态系统生产力预测的准确性,也是对植物光合适应机理认识的补充和深入。     

毛乌素沙地油蒿叶性状对光能利用效率动态的影响

目前对于荒漠灌木光能利用效率（LUE）的季节变异及其调控因素,尤其是其生物调控因素的认识非常有限,导致了荒漠生态系统生产力模型的不确定性。拟验证假设：长期干旱环境下,典型荒漠灌木油蒿光能利用效率日均值（LUE_day）的动态变化与叶片性状的季节性调整有关。试验采用Li-6400便携式光合仪定期测量了油蒿生长季叶片LUE_day的季节动态及相关叶性状指标,探究叶性状对LUE_day的影响。结果表明：LUE_day的季节波动范围为0.003-0.017 mol/mol,整体变异系数（CV）为38.75%。完全展叶期LUE_day均值相比生长季平均值降低17.37%,相比展叶期和落叶期时降低30%;8个叶性状的季节变异幅度差异较大,其中总叶绿素含量（Chl）、类胡萝卜素含量（Car）和叶氮含量（LNC）均表现出较大的季节变异性（CV ≥ 20%）,叶碳含量（LCC）和叶片相对含水量（LRWC）的变异程度最低（CV<7%）。LRWC与所有叶片化学性状（Chl、Chl a/b、Car、LNC和LCC）均存在显著相关,表明其变化与叶片的养分吸收、光合色素合成以及碳同化的运输过程密切相关;油蒿LUE_day的相对变化与LRWC、Chl a/b和LNC显著正相关,而LRWC和LNC的季节动态受空气温度（T_a）和土壤含水量（VWC）的共同调节,Chl a/b的季节波动主要由浅层土壤含水量（10 cm VWC）控制。以上研究结果强调,在未来预计极端的气候事件（如极端干旱和持续热浪事件）发生更频繁的旱地场景中,时间尺度植物叶性状对于土壤干旱和高温的适应性调整应当被充分考虑到旱地生态系统的通量建模方案中。该结果将为构建叶片尺度的光合生理模型与厘清LUE的生物调控机制提供理论依据。     

油蒿资源利用效率在生长季的相对变化及对环境因子的响应

为了探明西北半干旱区典型沙生植物油蒿(Artemisia ordosica)叶水平资源利用效率的相对变化及对环境因子的响应机制,该研究于2018年5–10月,使用LI-6400XT便携式光合仪测定了毛乌素沙地油蒿叶片的净光合速率(P_n)、蒸腾速率(E)、叶表面光合有效辐射(PAR_l)、叶表面温度(T_l)、叶表面相对湿度(RH_l),在实验室计算叶片单位面积氮含量(N_(area)),分析了叶片氮利用效率(NUE)、水分利用效率(WUE)、光利用效率(LUE)与环境因子之间的关系及NUE、WUE、LUE之间的相对变化。研究结果表明,在充足且稳定光强下油蒿的P_n主要受温度的影响,NUE、WUE与VPD_l、T_l之间具有显著负相关关系,NUE、WUE与LUE间为正相关关系,NUE、WUE和LUE最大值分别发生在5、7和9月,分别为9.43μmol CO_2·g~(–1)·s~(–1)、3.86 mmol·mol~(–1)、0.04mol·mol~(–1),资源利用效率的变化主要受P_n的影响。温度通过影响植物N分配来改变P_n,进而影响着资源利用效率,WUE与LUE显著正相关,对构建荒漠区生态系统能量交换过程模型有重要意义。     

沙质草地植物功能性状对放牧、增水、氮添加及其耦合效应的响应机制

人类活动和气候变化对陆地生态系统结构和功能的影响日益明显。在中国半干旱草原区,植物功能性状对这些变化的响应机制仍不是很清楚。以科尔沁沙质草地植物群落功能性状（CWM_trait）、一年生和多年生植物平均功能性状为研究对象,开展非生长季放牧、增水、氮添加及其耦合效应的模拟控制试验,于2016年8月中旬在沙质草地开展了植物功能性状的调查及测定,主要包括植物高度、比叶面积（specific leaf area,SLA）、叶片干物质含量（leaf dry matter content,LDMC）、叶片氮含量（leaf nitrogen content,LNC）和叶片碳同位素（leaf carbon isotopes,δ¹³C）。结果表明：氮添加显著提高了CWM_height和CWM_LNC（P<0.05）,降低了CWM_LDMC（P<0.05）,同时放牧和增水的耦合效应对CWM_SLA具有显著影响（P<0.05）;放牧显著降低了一年生植物的平均高度（P<0.05）,氮添加显著提高了一年生植物的平均高度、LNC和δ¹³C （P<0.05）;氮添加显著提高了多年生植物的平均SLA、LNC和δ¹³C （P<0.05）,同时放牧和增水的耦合效应对多年生植物的平均SLA和LDMC具有显著影响（P<0.05）。主成分分析表明,放牧促进了植物群落和多年生植物SLA与LDMC、LNC和δ¹³C之间的负相关关系,增水促进了植物群落和多年生植物高度与SLA之间的正相关关系以及LDMC、LNC和δ¹³C之间的正相关关系,说明多年生植物在调控沙质草地植物群落响应外界干扰时具有较强的主导性作用。非生长季放牧、生长季禁牧有利于沙质草地的可持续发展和管理,增水能够减缓放牧压力对于草地植物的影响,氮添加有利于植物同化δ¹³C,并提高植物叶片的水分利用效率。     

A new model for relationship between irradiance and the rate of photosynthesis in <Emphasis Type="Italic">Oryza sativa</Emphasis>

The calculated maximum net photosynthetic rate (P _N) at saturation irradiance (I _m) of 1 314.13 μmol m⁻² s⁻¹ was 25.49 μmol(CO₂) m⁻² s⁻¹, and intrinsic quantum yield at zero irradiance was 0.103. The results fitted by nonrectangular hyperbolic model, rectangular hyperbolic method, binomial regression method, and the new model were compared. The maximum P _N values calculated by nonrectangular hyperbolic model and rectangular hyperbolic model were higher than the measured values, and the I _m calculated by nonrectangular hyperbolic model and rectangular hyperbolic model were less than measured values. Results fitted by new model showed that the response curve of P _N to I was nonlinear at low I for Oryza sativa, P _N increased nonlinearly with I below saturation value. Above this value, P _N decreased nonlinearly with I.     

不同CO2浓度升高和氮肥水平对水稻叶绿素荧光特性的影响

为研究不同CO₂浓度升高和氮肥水平对水稻叶绿素荧光特性的影响,利用由开顶式气室（OTC）组成的CO₂浓度自动调控平台开展田间试验。以粳稻9108为试验材料,CO₂浓度设置CK（对照,环境大气CO₂浓度）、C₁（CO₂浓度比CK增加160 μmol/mol）和C₂（CO₂浓度比CK增加200 μmol/mol）3个水平;氮肥设置低氮（N₁：10 g/m²）、中氮（N₂：20 g/m²）和高氮（N₃：30 g/m²）3个水平。结果表明,在低氮条件下,与CK相比,C₁处理使拔节期的F_o上升4.8%（P=0.031）;C₂处理使拔节期的F_o上升6.3%（P=0.015）,F_v/F_m下降4.8%（P=0.003）,使孕穗期的F_o上升12.7%（P=0.039）,F_v/F_o下降18.2%（P=0.039）。在高氮条件下,与CK相比,C₂处理使灌浆期的F_m、F_v和F_v/F_m分别下降3.6%（P=0.039）、4.9%（P=0.013）和1.3%（P=0.039）。在中氮条件下,与CK相比,C₁和C₂处理的影响不明显。在整个生育期内,CO₂浓度升高与施氮处理交互作用对水稻叶绿素荧光特性的影响未到达显著水平。研究表明,大气CO₂浓度升高使水稻叶片光系统Ⅱ受损,抑制其电子传递能力、电子受体Q_A氧化还原情况、最大光化学效率和潜在活性,通过适量施氮可以有效地缓解其负面效应。     

Compensatory effects of elevated CO<Subscript>2</Subscript> concentration on the inhibitory effects of high temperature and irradiance on photosynthetic gas exchange in carrots

We determined the interactive effects of irradiance, elevated CO₂ concentration (EC), and temperature in carrot (Daucus carota var. sativus). Plants of the cv. Red Core Chantenay (RCC) were grown in a controlled environmental plant growth room and exposed to 3 levels of photosynthetically active radiation (PAR) (400, 800, 1 200 μmol m⁻² s⁻¹), 3 leaf chamber temperatures (15, 20, 30 °C), and 2 external CO₂ concentrations (C _a), AC and EC (350 and 750 μmol mol⁻¹, respectively). Rates of net photosynthesis (P _N) and transpiration (E) and stomatal conductance (g _s ) were measured, along with water use efficiency (WUE) and ratio of internal and external CO₂ concentrations (C _i/C _a). P _N revealed an interactive effect between PAR and C _a. As PAR increased so did P _N under both C _a regimes. The g _s showed no interactive effects between the three parameters but had singular effects of temperature and PAR. E was strongly influenced by the combination of PAR and temperature. WUE was interactively affected by all three parameters. Maximum WUE occurred at 15 °C and 1 200 μmol m⁻² s^{− 1} PAR under EC. The C _i /C _a was influenced independently by temperature and C _a. Hence photosynthetic responses are interactively affected by changes in irradiance, external CO₂ concentration, and temperature. EC significantly compensates the inhibitory effects of high temperature and irradiance on P _N and WUE.     

Specific leaf area, leaf nitrogen content, and photosynthetic acclimation of Trifolium repens L. seedlings grown at different irradiances and nitrogen concentrations

Clover seedlings were grown at different nitrogen concentrations (5, 10, 15, 20, 25 mM NO₃ ⁻, i.e. N₅ to N₂₅) and two irradiances, I (200 and 400 μmol m⁻² s⁻¹ of photon flux density, i.e. I ₂₀₀ and I ₄₀₀). Net photosynthetic rate (P _N), photosynthetic nitrogen use efficiency (PNUE), leaf chlorophyll (Chl) content, maximum photochemical efficiency (F_v/F_m), and actual photochemical efficiency of photosystem 2 (PS2) (Φ_PS2) increased from N₅ to N₁₅ and decreased with N₁₅ to N₂₅. P _N, PNUE, and Φ_PS2 were higher at I ₄₀₀ than at I ₂₀₀, but F_v/F_m and leaf Chl contents at I ₄₀₀ were lower than at I ₂₀₀. The effects of the N and I on specific leaf area (SLA) and N contents per unit dry mass (N_m) were similar, the SLA and N_m increased from N₅ to N₂₅ and they were higher at I ₂₀₀ than at I ₄₀₀. The nitrogen contents per unit area (N_a) increased from N₅ to N₂₀, but decreased from N₂₀ to N₂₅. The N_a was higher at I ₂₀₀ than at I ₄₀₀ when Trifolium repens grew at N₅ and N₁₀, but it was higher at I ₄₀₀ than at I ₂₀₀ at N₁₅ to N₂₅.     

Photosynthetic responses of apricot (<Emphasis Type="Italic">Prunus armeniaca</Emphasis> L.) to photosynthetic photon flux density,leaf temperature,and CO<Subscript>2</Subscript> concentration

Two cultivars (Katy and Erhuacao) of apricot (Prunus armeniaca L.) were evaluated under open-field and solar-heated greenhouse conditions in northwest China, to determine the effect of photosynthetic photon flux density (PPFD), leaf temperature, and CO₂ concentration on the net photosynthetic rate (P _N). In greenhouse, Katy registered 28.3 μmol m⁻² s⁻¹ for compensation irradiance and 823 μmol m⁻² s⁻¹ for saturation irradiance, which were 73 and 117 % of those required by Erhuacao, respectively. The optimum temperatures for cvs. Katy and Erhuacao were 25 and 35 °C in open-field and 22 and 30 °C in greenhouse, respectively. At optimal temperatures, P _N of the field-grown Katy was 16.5 μmol m⁻² s⁻¹, 21 % less than for a greenhouse-grown apricot. Both cultivars responded positively to CO₂ concentrations below the CO₂ saturation concentration, whereas Katy exhibited greater P _N (18 %) and higher carboxylation efficiency (91 %) than Erhuacao at optimal CO₂ concentration. Both cultivars exhibited greater photosynthesis in solar-heated greenhouses than in open-field, but Katy performed better than Erhuacao under greenhouse conditions.     

Photosynthetic response to precipitation/rainfall in predominant tree (<Emphasis Type="Italic">Ulmus pumila</Emphasis>) seedlings in Hunshandak Sandland,China

The responses of gas exchange and chlorophyll fluorescence of field-growing Ulmus pumila seedlings to changes in simulated precipitation were studied in Hunshandak Sandland, China. Leaf water potential (Ψ_wp), net photosynthetic rate (P _N), stomatal conductance (g _s), and transpiration rate (E) were significantly increased with enhancement of precipitation from 0 to 20 mm (p<0.01), indicating stomatal limitation of U. pumila seedlings that could be avoided when soil water was abundant. However, P _N changed slightly when precipitation exceeded 20 mm (p>0.05), indicating more precipitation than 20 mm had no significant effects on photosynthesis. Maximum photochemical efficiency of photosystem 2, PS 2 (F_v/F_m) increased from 0.53 to 0.78 when rainfall increased from 0 to 10 mm, and F_v/F_m maintained a steady state level when rainfall was more than 10 mm. Water use efficiency (WUE) decreased significantly (from 78–95 to 23–27 μmol mol⁻¹) with enhancement of rainfalls. P _N showed significant linear correlations with both g _s and Ψ_wp (p<0.0001), which implied that leaf water status influenced gas exchange of U. pumila seedlings. The 20-mm precipitation (soil water content at about 15 %, v/v) might be enough for the growth of elm seedlings. When soil water content (SWC) reached 10 %, down regulation of PS2 photochemical efficiency could be avoided, but stomatal limitation to photosynthesis remained. When SWC exceeded 15 %, stomatal limitation to photosynthesis could be avoided, indicating elm seedlings might tolerate moderate drought.     

Foreign exploration for Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) and associated natural enemies on avocado (Persea americana Miller)

Scirtothrips perseae Nakahara was discovered attacking avocados in California, USA, in 1996. Host plant surveys in California indicated that S. perseae has a highly restricted host range with larvae being found only on avocados, while adults were collected from 11 different plant species. As part of a management program for this pest, a “classical” biological control program was initiated and foreign exploration was conducted to delineate the home range of S. perseae, to survey for associated natural enemies and inventory other species of phytophagous thrips on avocados grown in Mexico, Guatemala, Costa Rica, the Dominican Republic, Trinidad, and Brazil. Foreign exploration efforts indicate that S. perseae occurs on avocados grown at high altitudes (>1500 m) from Uruapan in Mexico south to areas around Guatemala City in Guatemala. In Costa Rica, S. perseae is replaced by an undescribed congener as the dominant phytophagous thrips on avocados grown at high altitudes (>1300 m). No species of Scirtothrips were found on avocados in the Dominican Republic, Trinidad, or Brazil. In total, 2136 phytophagous thrips were collected and identified, representing over 47 identified species from at least 19 genera. The significance of these species records is discussed. Of collected material 4% were potential thrips biological control agents. Natural enemies were dominated by six genera of predatory thrips (Aeolothrips, Aleurodothrips, Franklinothrips, Leptothrips, Scolothrips, and Karnyothrips). One genus each of parasitoid (Ceranisus) and predatory mite (Balaustium) were found. Based on the results of our sampling techniques, prospects for the importation of thrips natural enemies for use in a “classical” biological control program in California against S. perseae are not promising.     

Molecular phylogeny of Phebalium (Rutaceae: Boronieae) and related genera based on the nrDNA regions ITS 1+2

Parsimony analyses of the internal transcribed spacer regions of nuclear ribosomal DNA (ITS 1 & ITS 2) for 38 taxa sampled from the Phebalium group (Rutaceae: Boronieae) and two outgroups confirm that, with the exception of Phebalium sensu stricto and Rhadinothamnus, six of the currently recognised genera within the group are monophyletic. The data indicate that Phebaliums. str. is paraphyletic with respect to Microcybe, and Rhadinothamnus is paraphyletic with respect to Chorilaena. Rhadinothamnus and Chorilaena together are the sister group to Nematolepis. Drummondita, included as an outgroup taxon, clustered within the ingroup as sister to Muiriantha and related to Asterolasia.The phylogeny suggests that the evolution of major clades within a number of these genera (e.g. Phebalium) relates to vicariance events between eastern and south-western Australia. Leionema is an eastern genus, with the most basal taxon being the morphologically distinct Leionema ellipticum from northern Queensland. Leionema also includes one species from New Zealand, but this species (as with some others) proved difficult to sequence and its phylogenetic position remains unknown. Taxonomic changes at the generic level are recommended.The authors wish to thank Paul G.Wilson, PERTH, for advice and discussion, and Paul Forster, BRI, for collecting and providing material of Leionema ellipticum. The project was supported by a Melbourne University Postgraduate Award (to BM), the Australian Biological Resources Study (ABRS), Australian Systematic Botany Society and Wolf Den (Australia) Investments.     

Entwicklungsgeschichte und Ultrastruktur von Pollenkitt und Exine bei nahe verwandten entomophilen und anemophilen Angiospermensippen derAlismataceae,Liliaceae, Juncaceae,Cyperaceae, Poaceae undAraceae

Some closely related members of the monocotyledonous familiesAlismataceae, Liliaceae, Juncaceae, Cyperaceae, Poaceae andAraceae with variable modes of pollination (insect- and wind-pollination) were studied in relation to the ultrastructure of pollenkitt and exine (amount, consistency and distribution of pollenkitt on the surface of pollen grains). The character syndromes of pollen cementing in entomophilous, anemophilous and intermediate (ambophilous or amphiphilous) monocotyledons are the same in principal as in dicotyledons. Comparing present with former results one can summarize: 1) The pollenkitt is always produced in the same manner by the anther tapetum in all angiosperm sub-classes. 2) The variable stickiness of entomophilous and anemophilous pollen always depends on the particular distribution and consistency of the pollenkitt, but not its amount on the pollen surface. 3) The mostly dry and powdery pollen of anemophilous plants always contains a variable amount of inactive pollenkitt in its exine cavities. 4) A step-by step change of the pollen cementing syndrome can be observed from entomophily towards anemophily. 5) From the omnipresence of pollenkitt in all wind-pollinated angiosperms studied one can conclude that the ancestors of anemophilous angiosperms probably have been zoophilous (i.e. entomophilous) throughout.

     

New species and new combinations in Peruvian Orchidaceae

seventeen new species and combinations are proposed in the generaChondrorhyncha, Cischweinfia, Cochlioda, Eloyella, Encyclia, Kefersteinia, Koellensteinia, Macroclinium, Rodriguezia, Solenidiopsis, andStenia. All new species are illustrated. A key is provided for 2-flowered species ofMacroclinium, PeruvianSigmatostalix, and PeruvianStenia. Solenidium (Solenidiopsis) peruvianum Schltr. is lectotypified.     

安徽牯牛降的丝孢菌Ⅰ

本文报导作者采自安徽枯牛降自然保护区的18种丝孢菌,分属于5个属,其中有3个新种:牛皮冻生尾孢(Cercospora paederiicola),山鸡椒假尾饱(Pseudocercospora litseae-cubebae),鸡血藤生假尾孢(P. millettiicola)和2个中国新纪录。文中对新种进行了描述及绘图,新记录种作了简要说明。研究的标本保存在中国科学院微生物研究所真菌标本室(HMAS)。     

Changes of dung beetle communities from rainforests towards agroforestry systems and annual cultures in Sulawesi (Indonesia)

Little is known about how tropical land-use systems contribute to the conservation of functionally important insect groups, including dung beetles. In a study at the margin of Lore Lindu National Park (a biodiversity hotspot in Central Sulawesi, Indonesia) dung-beetle communities were sampled in natural forest, young secondary forest, agroforestry systems (cacao plantations with shade trees) and annual cultures (maize fields), each with four replicates (n = 16 sites). At each site we used 10 pitfall traps, baited with cattle dung, along a 100 m transect for six 3-day periods. The number of trapped specimens and species richness at the natural forest sites was higher than in all land-use systems, which did not significantly differ. Each land-use system contained, on average, 75% of the species richness of the natural forest, thereby indicating their importance for conservation. However, a two-dimensional scaling plot based on NESS indices (m = 6) indicated distinct dung beetle communities for both forest types, while agroforestry systems and annual cultures exhibited a pronounced overlap. Mean body size of dung beetles was not significantly influenced by land-use intensity. Five of the six most abundant dung beetle species were recorded in all habitats, whereas the abundance of five other species was significantly related to habitat type. Mean local abundance and number of occupied sites were closely correlated, further indicating little habitat specialisation. The low dung beetle diversity (total of 18 recorded species) may be due to the absence of larger mammals in Sulawesi during historical times, even though Sulawesi is the largest island of Wallacea. In conclusion, the dung beetle fauna of the lower montane forest zone in Central Sulawesi appears to be relatively robust to man-made habitat changes and the majority of species did not exhibit strong habitat preferences.     

Taxonomic status of the species of the green algal genusNeochloris

Komárek has recently reviewed the various species assigned to the green algal genusNeochloris Starr (Chlorococcales, Chlorococcaceae) and removed those with uninucleate vegetative cells to a new genus,Ettlia. Watanabe & Floyd, unaware ofKomárek's work, also reviewed the species ofNeochloris and distributed them among three genera—Neochloris, Chlorococcopsis gen. nov., andParietochloris gen. nov.—on the basis of details of the covering of the zoospore and the arrangement of the basal bodies of the flagellar apparatus. This paper reconciles these two treatments and makes additional recommendations at the ranks of genus, family, order, and class.     

Die GattungKarschia — Bindeglied zwischen bitunicaten Ascomyceten und lecanoralen Flechtenpilzen?

The genusKarschia, in the earlier sense, including saprophytes and parasites on lichens, has been thought to be a non-lichenized parallel genus of the lichen genusBuellia. Modern workers included it on the one hand inBuellia, on the other hand combined it with bitunicate ascomycetes. It is now proved thatKarschia is heterogeneous and contains but superficially similar members both of the genusBuellia of theLecanorales and of typical or masked bitunicateAscomycetes. Therefore, it can not be regarded as a link betweenLecanorales andDothideales. The type species ofKarschia belongs to theDothideales.