EFFECT OF GROWTH REGULATORS ON CYNODON DACTYLON (L.) PERS., SORGHUM HALEPENSE (L.) PERS,AND CYPERUS ROTUNDUS L.*

Summary. Plants of Cynodon dactylon (L.) Pers., Sorghum helepense (L.) Pers. and Cyperus rotundus L. were treated with the following growth regulators by dipping or foliar spraying: chlormequat, N-dimethylamino succinamic acid (B–995), MH, 2-chloroethane phosphonic acid (ethephon), flurecol and chlorflurecol. Effects varied from stimulation to inhibition of aerial growth, increases in shoot number, and kill of plants. The effect of combinations of foliar spraying with ethephon, MH, flurecol or chlorflurecol followed after 2 days by spraying with the herbicides dalapon or aminotriazole activated with ammonium thiocyanate, was investigated. The herbicides applied alone had no marked effect but combinations were generally more toxic. Ethephon stimulated growth of C. dactylon but combination with dalapon was phytotoxic. MH sprayed alone and combinations of flurecol or chlorflurecol with dalapon or aminotriazole were highly inhibitory to S. halepense. None of the treatments completely inhibited regrowth of C. rotundus. Effets de diverses substances de croissance sur Cynodon dactylon (L.) Pers., Sorghum halepense (L.) Pers. et Cyperus rotundus L. Résumé. Des plantes de Cynodon dactylon (L.) Pers., de Sorghum halepense (L.) Pers. et de Cyperus rotundus L. ont été traitées par trempage ou pulvérisation folaire avec les substances de croissance suivantes: chlorméquat, adde N-diméthylamine succinique (B-995), hydrazide maléique, acide 2-chloroéthane phosphonique (éthéphon), flurécol et chlorflurécol. Les effets furent variables, depuis la stimulation jusqu'à l'inhibition de la partie aérienne, l'accroissement du nombre de tiges et la mort de la plante. L'auteur a étudié l'effet de combinaisons de pulvérisations foliaires avec l'éthéphon, I'hydrazide malélque. le flurécol ou le chlorflurécol suivies deux jours plus tard de traitements au dalapon ou à l'aminotriazole activé avec le thyocyanate d'ammonium. Les herbicides appliqués seuls n'eurent pas un effet marqué mais les combinaisons furent en général plus toxiques. L'éthéphon stimule la croissance de Cynodon dactylon, mais la combinaison avec le dalapon fut phytotoxique. L'hydrazide maléique appliqué seul et les combinaisons de flurécol ou de chlorflurécol avec le dalapon ou I'aminotriazole furent hautement inhibiteurs pour Sorghum halepense. Aucun des traitements n'inhiba completement la repousse de Cyperus rotundus. Wirkung von Wackstunsregulatoren auf Cynodon dactylon (L.) Pers., Sorghum halepense (L.) Pers. und Cyperus rotundus L. Zusammenfassung. Pflanzen von Cyrwdon dactylon (L.) Pers., Sorghum halepense (L.) Pers. und Cyperus rotundus L. wurden durch Eintauchen oder Blattspritzung mit folgenden Wachslun Lsregulatoren behandelt: Chlormequat, B-995, MH, 2-Chlorächanphosphonsaure (Ethephon), Flurenol und Chlorflurenol. Die erzielten Effekte variierten zwischen Stimulierung und Hemmung des Sprosswachstums, Erhöhung der Zahl der Triebe und Abtötung der Pflanzen. Die Herbizide Dalapon und Aminotriazol, letzteres mit Ammoniumthiocyanat aktiviert, wurden zwei Tage nach Blattsprilzung mit Ethephon, MH, Flurenol oder Chlorflurrnol angewandt und der Effekt der Kombinationen untersucht. Die kombinierten Behandlungen erhöhten die Toxizität, hingegen blieb die Anwendung von Herbiziden allein ohne merkliche Wirkung. Ethephon stimulierte das Wachstum von C dactylon, aber eine Kombination mit Dalapon war phytotoxisch. MH allein sowie Kombinationen von Flurenol oder Chlorflurenol mit Dalapon oder Aminotriazol wirkten auf S. halepense stark hemmend. Keine dieser Behandlungen konnte das Wiederaustreiben von C. rotundus vollständig verhindern     

EFFECT OF DICAMBA ON OXYGEN UPTAKE AND CELL MEMBRANE PERMEABILITY IN LEAF TISSUE OF CYPERUS ROTUNDUS L.

Summary. The effect of the herbicidal compound dicamba (2-methoxy-3,6-dichlorobenzoic acid) on the rate of oxygen uptake and on cell membrane permeability of leaf tissues of purple nutsedge ( Cyprus rotundus L.) was studied. Dicamba induced noticeable alterations in both the pattern of oxygen consumption and in permeability of the cells following spraying of the foliar parts of the plants. A pronounced decrease in respiratory rate was observed 5 days after treatment with 10⁻³ M dicamba, but the rate of oxygen uptake rose to approximately the level of the control 10 days after application of the herbicide. Permeability of the cell membranes decreased 5 days after treatment of the leaves with 10⁻² M or 10⁻³ M dicamba. The results indicate that the early disruption of the cell membranes might be related to the mode of action of the herbicide.     

EFFECT OF MINIMUM SOIL TEMPERATURE ON DIFFERENTIAL DISTRIBUTION OF CYPERUS ROTUNDUS AND C. ESCULENTUS IN THE UNITED STATES*

Summary. The response of tubers to low temperatures was investigated to gain insight into a physiological basis for the differential distribution of Cyperus esculentus L. (yellow nutsedge) and C. rotundus L. (purple nutsedge) in the United States. Only C. esculentus tubers survived the winter of 1968–69 in the field at Urbana, Illinois. Less than 10% of C. rotundus tubers survived at 2°C for 12 weeks, whereas more than 95% of C. esculentus tubers survived this treatment. Exposures to -2°C for 4 h or longer killed 50% of C. rotundus tubers, whereas - 6·5°C was required to kill 50% of C esculentus tubers. C. rotundus distribution is restricted to regions where the soil seldom freezes, whereas C. esculentus is distributed in regions where the soil temperatures often get below freezing. Survival of C. esculentus tubers in soil which frequently freezes may account for its wide distribution. Death of C. rotundus tubers in soils which freeze apparently is the reason why the species is restricted to the southeastern and southwestern regions of the U.S.A. L'Influence de la température du sol sur la répartition différentielle de Cyperus rotundus et de Cyperus esculentus aux Etats-Unis     

EFFECTS OF DESICCATION AND TEMPERATURE ON SURVIVAL OF CYPERUS ESCULENTUS TUBERS AND CYNODON DACTYLON RHIZOMES

Summary. The effects of all combinations of five desiccation treatments, two temperatures and three durations of desiccation on the survival of Cyperus esculentus tubers and two-node Cynodon dactylon rhizome fragments were examined in laboratory and glasshouse experiments.
Cyperus esculentus tuber survival was greater at 22°C than at 4°C. Duration of desiccation did not influence tuber survival, except at the lower temperature.
Survival of Cynodon dactylon rhizome fragments was greatly influenced by desiccation treatment, duration of desiccation and the interaction of these two factors. No buds survived when rhizomes reached 50% of their original weight, indicating good tolerance of desiccation since the original dry-matter content of rhizomes in this experiment was 41·2%.     

小麦条锈病病害流行空间动态电算模拟的初步探讨Ⅱ.椭圆形传播

 针对小麦条锈病的近距离传播,在已有的单项传播、圆形传播研究的基础上,本研究提出模拟某一较短时间(数小时)内多风向、变风速共同作用所致的子代病害椭圆形传播模型。它是统计该段时间内的主风向及相应的侧方向风和反方向风,以其风速之比确定椭圆形分布的长短轴半径的比例以及分布中心在长轴上的位置,建立一种偏心椭圆锥体模型。其横截面为一个个椭圆,椭圆轨迹可模拟病害的等密度曲线,高度代表病情,锥体体积可模拟病害总量。
把组建的子模型已有的时间动态模型串联或结合起来,组建了病害时空动态综合模型"XRZD-2"。     

小麦条锈病病害流行空间动态电算模拟的初步探讨——Ⅰ.圆形传播

 在国内已发表的两个小麦条锈病流行电算模拟模型的基础上,将研究的病害传播范围等分成一定大小的正方形小区,并以其为空间传播的计量单元,确定各小区的方位和间距。利用Mackenzie的病害直线传播梯度模型,通过试验建立回归预测式求得b值。并根据子代病叶总数与子代发病中心病情的定量关系,求出中心点病情a。再经过随机数转换和重叠侵染转换,与已有的日传染率、潜育期模型相结合,组建了"XRZD-1"电子计算机模拟模型。通过多次循环可以推算和打印出逐日的各小区病害数量及形象化图形。实现了病害时间动态和空间动态的协同模拟。     

匐柄霉对大丽轮枝菌生长及微菌核形成的影响

在离体条件下及棉花植株内测试了匐柄霉对大丽轮枝菌的抑制作用。结果表明,在离体条件下,匐柄霉菌的菌丝体或其培养滤液,对大丽轮枝菌的生长和微菌核形成均有影响。将形态发生变异,不能形成微菌核的大丽轮枝菌菌株转移至ＰＤＡ培养基后,其微菌核形成能力不再恢复。匐柄霉培养滤液的抑菌物质受热不稳定,１００℃处理１０分钟后活性丧失。抑菌物质经硫酸铵、乙醇沉淀初步测定,属非蛋白次生代谢产物。匐柄霉经接种可进入棉株体内,定殖率为７５％～１００％,分布于棉苗根、茎的维管束组织中。与轮枝菌先后或同时混合接种,匐柄霉可减轻棉花黄萎病的症状,以棉苗栽种前用匐柄霉菌分生孢子悬浮液沾根处理效果最明显。     

A COMPARISON OF THE GROWTH AND COMPETITION BEHAVIOUR OF SEEDLINGS AND PLANTS FROM RHIZOMES OF AGROPYRON REPENS (L.) BEAUV. AND AGROSTIS GIGANTEA ROTH

Summary. Seedlings and plants derived from single-node rhizome fragments of Agropyron repens and Agrostis gigantea were grown in au unheated glasshouse, separately or together with wheat ( cv. Kolibri), in sandy loam soil in well-spaced pots, adequately watered and moderately fertilized. Samples of crop and weeds were taken for growth analysis in mid- May, late June and early August (when the wheat was ripe).
On average, wheat decreased the weight of weed shoots by 84% and of rhizomes by 77%, but the weeds decreased the weight of wheat shoots by only 7% and of grain by 13%. Without wheat, seedlings of both weed species had, by late June, grown as much as plants from rhizomes, but with wheat, the weed seedlings were throughout most of the experiment more susceptible to competition than were plants from rhizomes. There was no simple relationship between the final dry weights of the weeds and the amount they decreased wheat yield: although Agropyron seedlings in competition with wheat were much lighter than Agrostis from rhizomes, they decreased grain yield of wheat as much, suggesting that they competed more intensely for a limiting factor, possibly nitrogen.
It is concluded that the faster initial growth rate of wheat seedlings relative to the weeds from rhizomes and a larger initial seed reserve relative to the weed seedlings enabled the wheat to dominate the weeds.
Comparaison de la croissance et comportement compétitif de plantules et de plantes issues de rhizomes d'Agropyron repens ( L.) Beauv. et d' Agrostis gigantea Roth     

引起马铃薯软腐的菊欧氏杆菌的生物型和血清型

 从全国23个省、市、自治区的46份马铃薯块标本中分离到25株菊欧氏杆菌(Erwinia carysanthemi).经58项细菌学性状的研究,发现它们在酒石酸钠,乳酸钠,丙酸钠,菊糖,蜜二糖,D—山梨醇等项反应中有差别.据此将这25个菌株分为3个生物型,其中生物型Ⅰ是来自江苏的10个菌株;生物型Ⅱ是来自四川仁寿县和彭县的,也是10个菌株;生物型Ⅲ共4个菌株来自河北和内蒙。生物型Ⅰ和Ⅱ与Dickey系统中的生物型Ⅱ相似,而生物型Ⅲ则与任何已划分的生物型都有一定差异.     

MORPHOLOGICAL,ANATOMICAL AND BIOCHEMICAL EFFECTS OF PROPACHLOR ON SEEDLING GROWTH*

Summary. The root and shoot growth of oat (Avena saliva L.) and squash (Cucurbita maxima Duchesne) was reduced in proportion to propachlor concentration. Corn (Zea mays L.) root growth was inhibited only by concentrations of 16 ppm and higher. Cell division in onion (Allium cepa L.) root tips was reduced by propachlor and totally inhibited by 16 ppm. Auxin-induced cell elongation of oat coleoptiles was inhibited in proportion to propachlor concentration. Propachlor treatment prevented the normal senescence of squash cotyledons by inhibiting the autolysis of proteinaceous and lipid reserves. Effets morphologiques, anatomiques et biochimiques du propachlore sur la croissance des plantules Riisumi.     

THE EFFECT OF COMPETITION FROM CEREAL CROPS ON THE GERMINATION AND GROWTH OF AVENA FATUA L. IN A NATURALLY-INFESTED FIELD

Summary. The effect of winter wheat, winter rye, winter barley, spring barley, and fallow cultivated as for a winter cereal, on germination and growth of wild oats ( A. fatua ) was investigated on a naturally-infested field. Treatments were continued for 2 years on the same plots and in the third year all plots were cropped with spring barley. Wild oats were not allowed to shed seeds.
A. fatua was controlled by a dense crop of an autumn-sown cereal. The crop genus was unimportant provided it grew well on the site; its effectiveness depended on its density when the wild oats germinated in spring. Winter wheat and winter rye were equally effective. Even in a light crop of barley, wild oats grew much less vigorously than on the fallow plots. Beyond a certain crop density dependent on soil fertility, further increase in crop did not decrease the size of wild oats. The heaviest crop did not completely suppress the wild oats.
The crop affected the wild oats mainly by decreasing growth of the seedlings, but under winter wheat and winter rye some wild oat seeds may have remained dormant, germinating in the spring barley in the third year, perhaps because the crops decreased the soil moisture content. Nitrogenous fertilizer increased the weight of both crops and wild oats. Barley was more severely affected by soil acidity than wild oats and on acid areas of barley plots the wild oats were larger than where the pH was higher. In wheat and rye which were scarcely affected by soil acidity the size of the wild oat plants was unaffected by soil pH.
L'effet du competition des céréales sur la germination et le développement d' Avena fatua dans un champ naturellement infesté .     

VARIATION IN GROWTH OF SEEDLINGS AND CLONES OF AGROPYRON REPENS (L) BEAUV.

Summary. The growth of Agropyron repens seedlings, or of clones derived from them, raised from seeds collected from different areas was compared; the growth of seedlings raised from seeds from single spikes and from seeds of a cross of two clones was also compared.
The number and length of shoots and the amount of rhizome produced differed between seedlings from different areas. Seedlings with a large weight of rhizomes often had a small weight of shoots. Many of the differences found between seedlings from different areas were confirmed by comparing clones established from some of them. Comparisons of both seedlings and clones showed that the percentage of shoots that developed spikes differed between genotypes; clones with the least weight of rhizome tended to have most weight of spikes. Large variations also occurred between clones established from seedlings from a given area, particularly in the way their dry weight was partitioned between primary and secondary shoots and in the time the spikes emerged.
The amount of rhizome per seedling varied greatly between seedlings from seeds from single spikes and from seeds from a cross of two clones. There was some evidence of a negative correlation between per cent shoot and per cent rhizome dry weight with seedlings from single spikes and between number of shoots and number of rhizomes per seedling with seedlings from a cross of two clones.
Variation en croissance de plantules issues de semences et de clones d' Agropyron repens (L) Beauv.     

EFFECTS OF LIGHT INTENSITY, PHOTOPERIOD AND NITROGEN ON THE GROWTH OF SEEDLINGS OF AGROPYRON REPENS (L.) BEAUV. AND AGROSTIS GIGANTEA ROTH

Summary. Seeding of Agropyron repens (L.) Beauv. und Agrostis gigantea Roth were grown in two photoperiods and with amounts of nitrogen. On two occasions plants transferred between photoperiods.
The early growth of the seedlings was increased most by increasing the light intensity, but later nitrogen had the greatest effect. In short photoperiods, plants of both species were decumbent and had many more shoots than in long photoperiods. At the end of the experiment, plants of both species responded more to nitrogen in bright than in dim light, and the dry weight of Agropyron was increased more than that of Agrostis by increased photoperiod and nitrogen.
Agropyron initiated rhizomes sooner than Agrostis ; it had fewer rhizomes but they were longer and thicker and weighed more. Brighter light, longer photoperiod and nitrogen all increased rhizome weight. Photoperiod did this mainly by producing more rhizomes, light by increasing thickness or density, and nitrogen by both. The effects of photoperiod and nitrogen on the rhizome dry weight of Agropyron , but not of Agrostis , were additive.
Transferring plants from short to long photoperiods or from long to short, respectively increased or decreased total growth, but had an opposite effect on the rhizomes.     

GROWTH AND SPRAY RETENTION OF WILD OAT AND FLAX IN RELATION TO HERBICIDAL SELECTIVITY*

Summary. The growth of wild oat (Avena fatua L.) was accompanied by an increase in the amount of spray retained per plant and per unit weight of plant, probably because the projected area (plan view) increased as the plant became larger. Flax (Linum usitatissimum L.) retained a fairly constant volume of spray per plant from the 8-leaf to the 35–40-leaf stages, so that the spray retained per unit plant weight decreased considerably as the plants grew. This was related to the decrease in projected area as a proportion of the whole. There was also a difference in retentivity between the cotyledons and true leaves; the cotyledons retained ten to twenty times more spray per unit weight. These results suggest that maximum selectivity would be achieved by spraying at an advanced stage of growth. Wild oat at the 3-leaf stage retained more than half the aqueous spray in the two leaf axils, while flax retained most on the cotyledons. Distribution was shown to be a probable reason for selectivity. Addition of a surfactant greatly increased retention by both species, but although the effect of a spray on wild oat might thereby be increased, under certain conditions injury to flax might be increased and the margin of selectivity reduced. Croissance et retention des bouillies herbicides par la folle-avoine et le lin en rapport avec la sélectivité     

新疆克里雅河绿洲形成、演变与综合整治

该文以新疆克里雅河实例，阐述了绿洲形成的年代，分布及主要类型，并根据现代环境、社会特征及绿洲的实际利用状况，论述及预测了克里雅河沿岸绿洲的发展趋势，对克里雅河绿洲的整治与合理利用提出了意见。     

新疆克里雅河绿洲形成、演变与综合整治

该文以新疆克里雅河实例，阐述了绿洲形成的年代，分布及主要类型，并根据现代环境、社会特征及绿洲的实际利用状况，论述及预测了克里雅河沿岸绿洲的发展趋势，对克里雅河绿洲的整治与合理利用提出了意见。     

STUDIES ON THE GROWTH OF SEEDLINGS OF AGROPYRON REPENS (L.) BEAUV AND AGROSTIS GIGANTEA ROTH.

Summary. The growth of seedlings of Agropyron repens (L.) Beauv. and Agrostis gigantea Roth, in pots was studied in two experiments in 1968 and 1969. In Experiment 1 their growth was compared with that of wheat and in Experiment 2 they were grown in sandy loam (Woburn) and silt loam (Rothamsted) soil at four levels of nitrogen. Both species grew faster than wheat, mainly because they had a larger leaf area ratio. Tillering began earlier in wheat, but continued longer in the grasses, which eventually had many more shoots. Ears emerged in the order: wheat before Agropyron before Agrostis. Although Agrostis had much lighter seeds than Agropyron, it grew faster, but Agropyron initiated rhizomes sooner, usually when it had 1–2 tillers and 4 leaves. Agrostis did not initiate rhizomes until it had at least 10 tillers and 6 leaves. In Experiment 2 the seedlings at first grew more in Woburn than in Rothamsted soil but later more in Rothamsted than in Woburn soil. There was no evidence of a species/soil interaction but nitrogen had more effect on both species in Woburn than in Rothamsted soil. Neither soil type nor nitrogen affected the time at which rhizomes were initiated. Etude de la croissance de plantules d'Agropyron repens (L.) Beauv. et d'Agrostis gigantea Roth. Résumé. La croissance de plantules A'Agropyron repens (L.) Beauv. et d'Agrostis gigantea Roth, cultivdes en pots a étéétudiée au cours de deux expériences en 1968 et 1969. Dans la premiére experience, leur croissance fut compareée à celle du blé et dans une seconde experiénce, ces deux espéces furent cultivées sur un sol sablo-limoneux (Woburn) et sur un sol argilo-limoneux (Rothamsted) á quatre niveaux d'azote. Les deux mauvaises herbes poussérent plus vite que le blé, principalement en raison de leur rapport plus éalevé de surface foliaire. Le tallage commenga plus tot chez le bié, mais se poursuivit plus longtemps chez les deux mauvaises herbes qui, en fin de compte, eurent plus de tiges. L'épiaison se produisit dans l'ordre suivant: bléa, Agropyron, Agrostis. Bien que I'Agrostis ait des semences plus petites que I'Agropyron, il poussa plus vite, mais I'Agropyron émit des rhizomes plus tôt, habituellement au stade 1 à 2 talles et 4 feuilles. L'Agrostis n'émit pas de rhizome avant d'atteindre au moins le stade 10 talles et 6 feuilles. Dans la deuxième experience, les plantules poussérent d'abord plus dans le sol de Woburn que dans celui de Rothamsted mais, plus tard, plus dans le sol de Rothamsted que dans Celui de Woburn. II ne fut pas décelé d'interaction entre le sol et les espéces, mais I'azote fit un effet plus marqué sur les deux espéces dans le sol de Woburn que dans celui de Rothamsted. Ni le type de sol, ni le niveau d'azote n'eurent d'influence sur l'époque à laquelle les rhizomes commencérent de croître. Untersuchungen zum Wachstum von Keirnpjlanzen von Agropyron repens (L.) Beauv. Und Agrostis gigantea Roih. Zusammenfassung. Das Wachstum von Keimpfianzen von Agropyron repens (L.) Beauv. und Agrostis gigantea Roth, in Töpfen wurde 1968 und 1969 in zwei Versuchen untersucht. In Versuch II wurde das Wachstum mit dem von Weizen verglichen. In Versuch II wurden sie in sandigen Lehmboden (Woburn) und Silt-Lehm-(Rothamsted) Boden bei vier Stickstoffstufen angezogen. Beide Arten wuchsen in erster Linie wegen ihres grösseren Blattflächenanteils schneller als Weizen. Die Bestockung begann fruher bei Weizen, zog sich jedoch bei den Gräsern, die schliesslich wesentlich mehr Halme hatten, langer hin. Ahrenschieben erfolgte am frühesten bei Weizen, dann bei Agropyron und schliesslich bei Agrostis. Obgleich Agrostis viel leichtere Samen hatte als Agropyron, wuchs es schneller, doch entwickelte Agropyron fruher Rhizome, nornialerweise bei 1–2 Bestockungstriebe und 4 Blättern. Agrostis entwickelte Rhizome nicht ehe es mindestens 10 Bestockungstriebe und 6 Blätter hatte. In Versuch II wuchsen die Keimpflanzen zunächst besser in Woburn- als in Rothamsted-Boden, später wieder besser in Rothamsted als in Woburn-Boden. Es gab keine Anhalts-punkte für eine Interaktion zwisehen den Arten und dem Boden, doch wirkte Stickstoff bei beiden Arten besser in Woburn- als in Rothamsted-Boden. Weder Bodentyp noch Stickstoffmenge beeinflussten den Beginn der Rhizombfldung.     

EFFECT OF GROWTH REGULATORS AND HERBICIDES ON NORMAL AND WOUND PERIDERM ONTOGENY IN FRAXINUS PENNSYLVANICA SEEDLINGS*

Summary. IAA, GA, kinetin, 2,4-D and naptalam were applied at 100 or 1000 ppm in lanolin to wounds made at the top of the hypocotyl of Fraxinus pennsylvanica Marsh. seedlings. Formation of normal periderm was prevented in the hypocotyl below the wounded tissue by 1000 ppm IAA or naptalam and 100 or 1000 ppm 2,4-D. IAA or naptalam at 100 ppm and GA or kinetin at 100 or 1000 ppm retarded normal periderm development. Wound periderm development was prevented only by 1000 ppm 2,4-D. Wound-stimulated development of normal periderm in tissues near the wound was prevented by 1000 ppm kinetin and 100 or 1000 ppm 2,4-D. Anomalous growths which appeared morphologically similar to nascent roots developed in the wounded hypocotyl section of seedlings treated with 1000 ppm naptalam and 100 or 1000 ppm 2,4-D. Identical growths were found in unwounded portions of the hypocotyl of seedlings treated with 100 or 1000 ppm 2,4-D. The data emphasize differences in physiological control of normal and wound periderm development. Effets de substances de croissance et d'herbicides sur l'onlogénie du pérderme normal ou blessé dans des plantules de Fraxinus pennsylvanica.     

油茶炭疽病的发生与蔓延

四年来,作者对油茶炭疽病的侵染途径、传播方式、发病的阶段性、特点和具体条件职及病害蔓延等規律进行了研究。 結果指出,病菌侵染途径以伤口为主,也可能从自然孔道侵害果实。潛育期随气温上升而縮短,15℃至28℃时,潛育期由15天缩短为5天。分生孢子借助雨滴、风夹雨进行传播,干燥气流不能传菌。林間象(虫甲)、螞蚁不是传病的主要媒介。病害发生具有鮮明的季节性。果实发病期长,自4月至10月。病害有初期、中期、盛期和末期四个时期。感病宿主存在、菌源量积累和高温降雨为病害发生、发展的决定性因素。病害发展有間歇期和消长期。植株发病类型有:早发型、中发型、后发型及突发型四种。病果类型有:内侵型、邻侵型和外侵型三种。油茶炭疽病的逐年蔓延速度在一年内为36.5—50.0％;二年内为51.9—60.3％;三年内为55.8—61.8％。