甜菜碱对干旱胁迫下湖北海棠超微弱发光及抗氧化能力的影响

以盆栽4年生的苹果砧木湖北海棠（Malus hupehensis）为试材,叶面喷施100 mmol·L^-1的甜菜碱,研究外源甜菜碱对干旱胁迫下湖北海棠叶片超微弱发光（UWL）、丙二醛(MDA)、超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢（H₂O₂）、脯氨酸（Pro）及甜菜碱（GB）含量的影响.结果表明,轻度干旱胁迫下,叶片UWL强度提高,但随着干旱胁迫程度的加重而下降,至严重干旱胁迫时UWL明显低于正常供水处理;H₂O₂、MDA含量随干旱胁迫加重而升高;SOD和POD活性随胁迫加重而升高,但至重度干旱时下降.与单独干旱处理相比,叶片喷施甜菜碱显著提高了轻度和中度干旱胁迫叶片的UWL（分别提高35.27%和43.95%）、SOD和POD活性,降低了H₂O₂和MDA含量;促进了Pro和GB的积累.表明甜菜碱及通过甜菜碱诱导的脯氨酸积累,能够提高干旱胁迫下叶片的抗氧化能力,减轻过氧化损伤,对叶片细胞起到保护作用.     

大豆脯氨酸积累相关基因家族鉴定及干旱胁迫表达分析北大核心CSCD

脯氨酸是一种广泛存在的渗透调节物质,在植物生长发育以及响应干旱胁迫的信号途径中具有重要作用。吡咯啉-5-羧酸合成酶(P5CS)、鸟氨酸转氨酶(δ-OAT)、吡咯啉-5-羧酸还原酶(P5CR)、脯氨酸脱氢酶(Pro DH)、吡咯啉-5-羧酸脱氢酶(P5CDH)、脯氨酸转运体(Pro T)是影响植物体内脯氨酸积累的关键酶。但关于大豆脯氨酸积累相关基因家族成员的研究尚未见报道。本研究在大豆基因组中鉴定出7个Gm P5CS、2个Gm OAT、2个Gm P5CR、5个Gm Pro DH、3个Gm P5CDH及6个Gm Pro T基因,不均匀地分布在大豆20条染色体中的12条上,发生16对片段复制事件。系统进化树分析发现,大豆脯氨酸积累相关基因家族分为不同的进化分支,同一亚族间的基因结构和保守基序相似。顺式作用元件分析结果显示,脯氨酸积累相关基因家族含响应逆境胁迫及植物激素的顺式作用元件。干旱胁迫下的表达模式分析结果显示,脯氨酸合成代谢相关基因家族成员(Gm P5CS、Gm OAT、Gm P5CR)响应干旱胁迫,在干旱胁迫24 h时显著上调表达;大多脯氨酸分解代谢相关基因家族成员(Gm Pro DH、Gm P5CDH)下调表达,脯氨酸转运相关基因家族成员(Gm Pro T)在干旱胁迫24 h显著上调表达,其中Gm P5CS5、Gm OAT1、Gm Pro T2、Gm Pro T4及Gm Pro DH3~5基因在干旱胁迫下的脯氨酸积累中可能起到关键作用。大豆幼苗P5CS、OAT活性随干旱胁迫时间的延长呈显著上升的趋势,与脯氨酸的积累呈正相关:Pro DH活性随干旱胁迫时间的增长呈显著下降的趋势,与脯氨酸的积累呈负相关。本研究为进一步解析大豆脯氨酸积累相关家族基因响应干旱胁迫的功能提供了参考。     

干旱胁迫下蒭雷草的生理响应

为探讨蒭雷草(Thuarea involuta)在热带珊瑚岛干旱环境下的适应能力,对干旱胁迫下蒭雷草叶片抗逆生理指标的变化进行了研究。结果表明,干旱胁迫初期,叶片的丙二醛(MDA)含量随胁迫程度增加的差异不显著;随胁迫时间的延长,除重度胁迫下先迅速增加后急速下降外,其余处理的变化较小。超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性随干旱胁迫程度增加而升高;随时间延长,SOD活性不断上升,POD活性基本稳定,CAT活性则先下降后上升。除轻度胁迫下可溶性蛋白(SP)含量低于对照外,其余处理均随干旱胁迫程度增加而增加;干旱胁迫下的脯氨酸(Pro)含量随时间延长呈先上升后下降的变化趋势,但在处理第18天时不同胁迫程度间均差异不显著。因此,蒭雷草具有较强的抗旱能力,可用于南海诸岛的人工植物群落构建和植被恢复以营造良好生态环境。     

外源SNP对干旱胁迫下不同马铃薯品种叶片抗氧化酶活性的影响

以正常水分状态、轻度干旱胁迫、中度干旱胁迫和重度干旱胁迫下的马铃薯抗旱品种‘底西瑞’和干旱敏感品种‘大西洋’ 植株为材料,于现蕾期采用0（对照）和0.01 mmol·L^-1 SNP分别喷施各处理植株,对不同处理下2个品种的植株形态、叶片超氧阴离子和H₂O₂含量以及抗氧化酶活性进行比较分析,探讨外源SNP对干旱状态下马铃薯的生理应答机制,为马铃薯的抗旱栽培提供新的技术理论支持。结果显示：（1）SNP喷施对重度水分胁迫下马铃薯植株的正常生长具有一定的保护作用。（2）在干旱胁迫条件下,马铃薯叶片POD活性在品种‘底西瑞’中增加而在品种‘大西洋’中降低,超氧阴离子含量和H₂O₂含量以及CAT和APX活性在各品种中均增加,但超氧阴离子含量和H₂O₂含量增加程度与胁迫程度无关。（3）抗旱品种‘底西瑞’在干旱胁迫下的超氧阴离子含量低于干旱敏感品种‘大西洋’,而其POD、CAT和APX活性则高于‘大西洋’; 0.01 mmol·L^-1SNP处理未改变马铃薯叶片中超氧阴离子和H₂O₂含量随土壤水分的变化趋势,但改变了‘大西洋’叶片中SOD、POD、CAT活性以及‘底西瑞’叶片中APX活性的变化趋势。（4）外源喷施0.01 mmol·L^-1SNP降低了‘底西瑞’在中度和重度胁迫下以及‘大西洋’在轻度和中度胁迫下超氧阴离子含量,提高了干旱胁迫下‘底西瑞’和‘大西洋’的POD和APX活性。研究表明,POD、CAT和APX可作为马铃薯水分胁迫下的应答以及品种抗旱性的筛选指标,外源SNP可通过诱导增强干旱胁迫下马铃薯的抗氧化酶活性来提高其抗旱性。     

水分胁迫对黄檗幼苗保护酶活性及脂质过氧化作用的影响

以轻度干旱、重度干旱和水涝处理黄檗幼苗,测定丙二醛(MDA)和游离脯氨酸含量及超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性的动态变化.结果表明,处理40 d以后,轻度干旱、重度干旱和水涝处理的叶片MDA含量始终显著高于对照,最高分别达对照的2.9、2.37和4.12倍,三者之间在处理80 d以后MDA含量差异不显著.水涝处理和对照的游离脯氨酸含量在处理期间没有明显变化,干旱处理的游离脯氨酸含量从处理后40 d开始增加、80 d后回落,重度干旱处理的增加幅度显著大于轻度干旱处理.SOD、POD和CAT活性的变化趋势缺乏一致性,但重度干旱处理的黄檗幼苗,叶片的SOD、POD和CAT活性在处理期间始终显著高于轻度干旱、水涝处理和对照.     

外源ABA对低温胁迫下小桐子幼苗脯氨酸积累及其代谢途径的影响

本文以小桐子为材料,研究了外源脱落酸（ABA）对低温胁迫下小桐子幼苗脯氨酸积累的影响。结果表明,低温胁迫（5℃）可促进小桐子幼苗体内脯氨酸的积累,上调脯氨酸合成关键酶Δ¹-吡咯琳-5-羧酸合成酶（P5CS）和鸟氨酸转氨酶（OAT）的活性,上调P5CS基因（JcP5CS）的表达,及抑制脯氨酸降解酶脯氨酸脱氢酶（Pro DH）的活性。用外源ABA处理低温胁迫下的小桐子幼苗,发现150μmol·L^-1的ABA可显著提高其低温胁迫下的脯氨酸含量,上调P5CS的活性和JcP5CS的表达水平,及抑制ProDH的活性。表明外源ABA可通过活化脯氨酸合成的谷氨酸途径和抑制脯氨酸的降解途径来促进低温胁迫下小桐子幼苗脯氨酸的积累。     

干旱胁迫及复水对香樟幼树生理特性及生长的影响

通过盆栽和持续干旱处理研究了轻度干旱(持续干旱2~4d)、中度干旱(持续干旱6~8d)和重度干旱胁迫(持续干旱10~16d)及复水对香樟(Cinnamomum camphora)幼树生理特性和生长的影响,为香樟育苗、造林及合理的水分管理提供理论依据。结果显示:(1)干旱胁迫下香樟幼树地径生长量(Zd)和树高生长量(Zh)受到了抑制;轻度、中度干旱处理(土壤体积含水量从正常状态下降到7%)下叶片相对含水量(LRWC)与对照差异不显著,重度干旱处理(土壤体积含水量下降到3%)下显著低于对照。(2)轻度、中度干旱处理的超氧阴离子和过氧化氢含量与对照无显著差异,重度干旱处理较对照显著上升。(3)在活性氧酶促清除系统中,超氧化物歧化酶(SOD)、过氧化物酶(POD)活性在轻度干旱时显著上升,而过氧化氢酶(CAT)活性在重度干旱时才显著上升,在复水48h后3种酶活性均恢复到对照水平。(4)在轻度、中度干旱处理中叶片丙二醛(MDA)含量无显著变化,而在重度干旱下显著升高,且复水48h后未见显著降低。(5)在渗透调节物质中,轻度干旱时可溶性蛋白(SP)含量开始显著升高,中度干旱时可溶性糖(SS)含量显著升高,重度干旱时脯氨酸(Pro)含量显著上升;复水48h后Pro含量显著降低,而可溶性蛋白和可溶性糖含量无显著变化。研究发现,香樟幼树在轻度干旱胁迫下能通过自身抗氧化酶系统和渗透调节物质维持正常生长,而在中度和重度干旱胁迫条件下,其水分生理状况变差,膜系统遭受伤害,酶活性受到抑制,最终导致其形态生长和地上部分生物量积累受限。     

外源脯氨酸对盐胁迫下甜瓜脯氨酸代谢的影响

为探明外源脯氨酸对盐胁迫下甜瓜脯氨酸代谢的影响,以甜瓜品种‘雪美’为材料采用营养液栽培,对盐胁迫(100mmol·L-1 NaCl)、盐胁迫下添加外源脯氨酸(100mmol·L-1 NaCl+0.2mmol·L-1 Proline)以及对照3种处理后甜瓜幼苗叶片脯氨酸(Pro)含量、吡咯啉-5-羧酸合成酶(P5CS)、鸟氨酸转氨酶(OAT)和脯氨酸脱氢酶(ProDH)活性进行测定,并对OAT和ProDH基因进行克隆及半定量表达分析。结果显示:与对照相比较,盐胁迫条件下甜瓜幼苗叶片内Pro含量显著增加,P5CS活性增幅大于OAT活性,OAT基因表达量大部分时段内没有增加,ProDH活性下降,ProDH基因表达量减少;盐胁迫下添加外源脯氨酸进一步使幼苗叶片内Pro含量增加、OAT、ProDH活性提高、P5CS活性降低,并且使OAT基因表达量迅速增加、ProDH基因表达量先增加后回落。研究表明,盐胁迫条件下,甜瓜幼苗体内脯氨酸积累主要是通过增强脯氨酸的谷氨酸合成途径和抑制脯氨酸降解来实现;适量外源脯氨酸可以增强盐胁迫幼苗脯氨酸的鸟氨酸合成途径,但对谷氨酸合成途径有一定的抑制作用;通过调节合成和降解2种代谢途径进一步提高了脯氨酸含量,从而增强甜瓜幼苗耐盐胁迫能力。     

外源水杨酸对盐胁迫下小桐子幼苗脯氨酸代谢的影响

以小桐子幼苗为材料,设置盐胁迫(200mmol·L-1 NaCl)和外源水杨酸处理(0~2.0mmol·L-1 SA)水培试验,通过检测幼苗叶片脯氨酸含量、脯氨酸代谢关键酶活性及相关代谢酶基因的表达水平,研究了外源水杨酸对盐胁迫下小桐子幼苗脯氨酸代谢机理的影响。结果显示:(1)外源0.9mmol·L-1 SA处理可显著提高盐胁迫下小桐子幼苗的脯氨酸含量,上调脯氨酸合成关键酶Δ1-吡咯琳-5-羧酸合成酶(P5CS)和鸟氨酸转氨酶(OAT)活性,以及上调JcP5CS和JcOAT基因的表达水平。(2)SA也显著抑制了脯氨酸降解酶ProDH的活性及JcProDH基因的表达水平。(3)SA处理还显著提高了盐胁迫下小桐子幼苗的组织活力,降低了叶片电解质渗漏率和丙二醛(MDA)含量。研究发现,外源SA可通过活化脯氨酸合成的谷氨酸途径和鸟氨酸途径,以及抑制脯氨酸的降解途径来促进盐胁迫下小桐子幼苗脯氨酸的积累;外源SA处理也可提高小桐子幼苗的耐盐性,且这种提高可能与SA诱导脯氨酸的积累密切相关。     

干旱胁迫对玉米苗期叶片光合作用和保护酶的影响

以玉米品种郑单958(抗旱性强)和陕单902(抗旱性弱)为材料,采用盆栽控水试验,设置3个干旱处理(轻度干旱,中度干旱,重度干旱)和正常灌水,研究了干旱胁迫对玉米苗期叶片光合速率、叶绿素荧光以及相关生理指标的影响。结果表明:(1)干旱胁迫下2个品种叶片净光合速率(P_n)和气孔导度(G_s)显著下降,胞间CO₂浓度(C_i)出现了先下降后上升,而气孔限制值(L_s)上升后下降,说明中度干旱胁迫下叶片P_n下降是气孔因素引起的,重度干旱胁迫下P_n降低主要由非气孔因素引起的。(2)随着干旱胁迫的加剧,2个品种叶片光系统Ⅱ(PSⅡ)的实际量子产量(φPSⅡ)、电子传递速率(ETR)和光化学猝灭(qP)一直下降,而非光化学猝灭(qN)上升后下降,说明中度干旱下热耗散仍是植株重要光保护机制,重度干旱时叶片光合电子传递受阻,PSⅡ受到损伤。(3)干旱胁迫下2个品种叶片的超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性先升高后降低,而丙二醛(MDA)含量一直升高,说明干旱胁迫初期对保护系统酶活性升高有诱导作用,重度胁迫下活性氧清除酶的活性下降,导致细胞膜伤害。这些结果暗示,轻度和中度干旱胁迫下2个玉米品种通过减少光捕获、热耗散和酶活性调节协同作用稳定了光合机构功能,是P_n下降的气孔限制因素;而重度干旱胁迫下光系统Ⅱ和抗氧化酶系统损伤,是P_n下降的非气孔限制因素;郑单958的各生理参数比陕单902受旱影响小,干旱胁迫下仍具有较高的光合效率和较强的保护酶活性是郑单958抗旱的主要生理原因。     

Y-chromosome Data and Tribal Affiliations of Allenopithecus and Miopithecus

The phylogeny of Old World monkeys has remained unresolved in part because of a lack of resolution in the Cercopithecinae. Competing morphological hypotheses have had Allen's swamp monkey (Allenopithecus nigroviridis) and the talapoins (Miopithecus spp.) as basal branches of either the tribe Cercopithecini or the tribe Papionini. Previous molecular analyses have not adequately addressed the issue. To better understand the evolutionary history of these primates, we sequenced and subjected to phylogenetic analysis 3.1 kb of 2 loci (TSPY and SRY) from the non-recombining portion of the Y-chromosome. Individuals from the genera Allenopithecus, Miopithecus, Erythrocebus, Chlorocebus, and Cercopithecus were surveyed and their sequences compared with those previously published for the Papionini and Colobinae. The results suggest Allenopithecus and Miopithecus are more closely related to the Cercopithecini than Papionini. Our data also support the hypothesis that within the Cercopithecini, Erythrocebus and Chlorocebus share a close evolutionary relationship, distinct from the other members of the tribe.     

Nystatin and killer toxin sensitivity of free and immobilizedSaccharomyces cerevisiae

The inhibitory effect of nystatin and killer toxin on the growth of free and covalently-immobilizedSaccharomyces cerevisiae cells was studied. The resistance of immobilized cells to both agents was accompanied by increased amounts of phospholipids and sterols. The possible relationship between these changes in the membrane composition and the transduction of a signal across the cytoplasmic membrane is discussed.     

The hernandez and fernandez genes of Drosophila specify eye and antenna

The formation of different structures in Drosophila depends on the combined activities of selector genes and signaling pathways. For instance, the antenna requires the selector gene homothorax, which distinguishes between the leg and the antenna and can specify distal antenna if expressed ectopically. Similarly, the eye is formed by a group of "eye-specifying" genes, among them eyeless, which can direct eye development ectopically. We report here the characterization of the hernandez and fernandez genes, expressed in the antennal and eye primordia of the eye-antenna imaginal disc. The predicted proteins encoded by these two genes have 27% common amino acids and include a Pipsqueak domain. Reduced expression of either hernandez or fernandez mildly affects antenna and eye development, while the inactivation of both genes partially transforms distal antenna into leg. Ectopic expression of either of the two genes results in two different phenotypes: it can form distal antenna, activating genes like homothorax, spineless, and spalt, and it can promote eye development and activates eyeless. Reciprocally, eyeless can induce hernandez and fernandez expression, and homothorax and spineless can activate both hernandez and fernandez when ectopically expressed. The formation of eye by these genes seems to require Notch signaling, since the induction of ectopic eyes and the activation of eyeless by the hernandez gene are suppressed when the Notch function is compromised. Our results show that the hernandez and fernandez genes are required for antennal and eye development and are also able to specify eye or antenna ectopically.     

Molecular identification and differentiation of Brevibacterium species and strains

Amplified ribosomal DNA restriction enzyme analysis (ARDRA), pulsed field gel electrophoresis (PFGE) and ribotyping were used to differentiate among 24 strains of Brevibacterium linens, Brevibacterium casei and Brevibacterium epidermidis obtained from type culture collections or isolated from various smear ripened cheeses. ARDRA was applied to the 16S rDNA. B. linens was shown to be a quite heterogenic group with 2 to at least 4 copies of rrn operons per strain with aberrant nucleotide sequences. AccI gave genus specific restriction patterns and was used to separate Brevibacterium from Corynebacterium species. The expected species specificity of TaqI applied to B. linens type culture strains, but not to all strains isolated from cheese. By AvaI restriction, B. casei and B. linens were differentiated from B. epidermidis and the orange pigmented Arthrobacter casei, a new species of coryneform bacteria; by XmnI restriction, B. linens and B. epidermidis were differentiated from B. casei. One of 4 B. linens genotypes could not be distinguished from B. casei by this method. Here, the typical orange B. linens pigments were used for classification, which was confirmed by partial sequencing of the 16S rDNA.     

Evaluation of antiprotozoal and antimycobacterial activities of the resin glycosides and the other metabolites of Scrophularia cryptophila

Resin glycosides are secondary metabolites exclusive to the convolvulaceous plants. In this study, crypthophilic acids A–C (1–3), the first resin glycosides occurring in another family (Scrophulariaceae), and the other constituents of Scrophularia cryptophila were examined for in vitro antiprotozoal and antimycobacterial potentials. Except for crypthophilic acid B (2), all tested compounds exhibited growth-inhibitory effect against Trypanosoma brucei rhodesiense, with l-tryptophan (6) and buddlejasaponin III (7) being the most potent ones (IC₅₀'s 4.1 and 9.7 μg/ml). In contrast, the activity towards Trypanosoma cruzi was poor, and only crypthophilic acid C (3), 6 and 7 were trypanocidal at concentrations above 40 μg/ml. With the exception of 2 and 6, all compounds were active against Leishmania donovani. Harpagide (4) and 3 emerged as the best leishmanicidal agents (IC₅₀'s 2.0 and 5.8 μg/ml). Only compounds 3, 6 and 7 showed antimalarial activity against Plasmodium falciparum with IC₅₀ values of 4.2, 16.6 and 22.4 μg/ml. Overall the best and broadest spectrum activity was presented by compounds 3 and 7, as they inhibited all four parasitic protozoa. None of the isolates had significant activity against Mycobacterium tuberculosis (MICs >100 μg/ml) or were toxic towards mammalian (L6) cells. This is the first report of antiprotozoal activity for natural resin glycosides, as well as for harpagide (4), acetylharpagide (5), tryptophan (6) and buddlejasaponin III (7).     

Theoretical Study of Antagonists and Inhibitors of Mammalian Adenosine Deaminase: I. Adenosine and Its Aza- and Deazaanalogues

Aza- and deazaanalogues of adenosine, including their 1-protonated forms (except for that of 1-deazaadenosine), were studied by computer computation to find a relationship between their molecular structures and substrate properties for the mammalian adenosine deaminase. The atomic charge distribution and maps of the electrostatic potential around their van der Waals molecular surface were calculated for these compounds using the ab initio STO-3G method. The conformational studies are carried out by the MM⁺ method of molecular mechanics. The mechanism that determines the substrate selectivity of mammalian adenosine deaminase is discussed.     

Pericarp structure and phylogeny of theLamiaceae-Verbenaceae-complex

Pericarp structure was investigated in 158 species of the familiesLamiaceae andVerbenaceae. Data from 221 out of 262 genera ofLamiaceae s.l. and a few ofVerbenaceae s.str. were collected in a table. A cladistic analysis was performed on the basis of pericarp characters only. The abandonment of subfam.Pogostemonoideae as a taxonomic unit is considered. Examples of groups given additional support by similarities in pericarp characters are: (1) the gynobasic-styled labiates (subfamiliesPogostemonoideae, Lamioideae, Nepetoideae); (2) aLamioideae-Pogostemonoideae-group; (3)Nepetoideae; (4) aWestringia-Hemigenia-Hemiandra-Microcorys group (in subfam.Chloranthoideae); (5) aLepechinia-Chaunostoma-group (inNepetoideae); (6) aPrunella-Cleonia-group (inNepetoideae).     

Effects of carbon concentration and carbon to nitrogen ratio on the growth and sporulation of several biocontrol fungi

Effects of carbon concentration and carbon to nitrogen (C:N) ratio on six biocontrol fungal strains are reported in this paper. All fungal strains had extensive growth on the media supplemented with 6–12 g l⁻¹ carbon and C:N ratios from 10:1 to 80:1, and differed in nutrient requirements for sporulation. Except for the two strains of Paecilomyces lilacinus, all selected fungi attained the highest spore yields at a C:N ratio of 160:1 when the carbon concentration was 12 g l⁻¹ for Metarhizium anisopliae SQZ-1-21, 6 g l⁻¹ for M. anisopliae RS-4-1 and Trichoderma viride TV-1, and 8 g l⁻¹ for Lecanicillium lecanii CA-1-G. The optimal conditions for P. lilacinus sporulation were 8 g l⁻¹ carbon with a C:N ratio of 10:1 for M-14 and 12 g l⁻¹ carbon with a C:N ratio of 20:1 for IPC-P, respectively. The results indicated that the influence of carbon concentration and C:N ratio on fungal growth and sporulation is strain dependent; therefore, consideration for the complexity of nutrient requirements is essential for improving yields of fungal biocontrol agents.     

Origin and development of Tool-making behavior in Africa and Asia

Around two-and-a-half million years ago, some hominid populations in Africa began to modify stones and bones in a manner that can be recognized by prehistorians as artifacts, and, by definition, produced the earliest identifiable archaeological record. It is likely that earlier hominid groups also may have had relatively rich tool-using behavioral repertoires similar to that seen in modern chimpanzees (McGrew, 1992), such tools may have been made of perishable materials or minimally modified and thus difficult to identify. This review will focus on the earliest archaeological traces and the spread of hominids out of Africa and into Eurasia.     

Spatial and temporal patterns of morel fruiting

The biotic and abiotic factors conditioning morel fruit body production are incompletely known. We examined spatial and temporal patterns of Morchella esculenta fruiting over five years in a wooded site in Missouri, USA. Fruiting onset was inversely correlated with spring air and soil temperatures, whereas abundance was positively correlated with rain events (>10 mm) during the 30 d preceding fruiting. The two years with the greatest fruiting had the shortest fruiting seasons (6–7 d). Fruiting season length was positively correlated with soil warming, suggesting that a narrow range of optimum soil temperatures favour the explosive production of fruit bodies. All woody stems of at least 1 cm diam were mapped and stem diameter and crown condition were noted. Morel fruit bodies were significantly closer to stems of Carya spp., Tilia americana and Ulmus americana than predicted by the frequencies of these woody species or their contribution to the total basal area on the site. Although intra-annual clustering of fruit bodies was often observed, inter-annual clustering was not. The spatial pattern of M. esculenta fruiting appears to be associated with vegetation pattern, whereas the onset and abundance of fruiting are determined by the interaction of spring temperatures with availability of supporting precipitation.