SPATIAL GROWTH OF CYNODON DACTYLON (L.) PERS.*

Summary. Small sprigs of Cynodon dactylon (L.) Pers., were planted and grown without competition from weeds and crops for 2 1/2 years. The plant spread by means of above-ground creeping stolons and subterranean rhizomes which could also emerge as aerial shoots, producing in their turn new stolons and rhizomes. Initially there was linear extension of stolons and rhizomes, following which gaps in the sod were filled by stolon branching and new shoots. There was no preferential direction of stolon elongation and established sods developed an approximately circular shape and expanded concentrically. The rate of increase in sod area was similar in both years of observation but radial extension was smaller in the second year than in young plants. The mean sod area was 25 m² after 2½ years of growth, and mean monthly area increment was 0·9 m². Growth almost stopped in the cold season and exceeded 2 m² per month in the summer. The plants had extended up to 3·9 m from the plant centre after 2 1/2 years. The number of flowering culms per sod, produced only in the warm season, was directly proportional to sod area; seeds were infertile in the Newe Ya'ar area. After 2½ years of growth about 70% of the rhizome dry weight was present in the upper 20 cm of soil. Few rhizomes penetrated deeper than 40 cm. More than 60% of the rhizomes were present within 1 m radius of the plant centre and 90% were present within 2 m radius. Croissance spatiale de Cynodon dactylon (L.) Pers.     

Johnsongrass (Sorghum halepense) growth characteristics as related to rhizome length

Growth characteristics of johnsongrass [Sorghum halepence(L) Pers] grown in the field from rhizomes 2.5, 5, 10, 15, 20, or 25 cm long were studied in a sandy loam soil for 2 years. Plant height, number of leaves per plant, number of tillers per plant, and fresh weight of new rhizomes and shoots were significantly dependent on the length of the planted rhizome 20, 40, 60, or 80 days after planting. All growth characteristics increased significantly as the length of planted rhizome increased from 2.5 cm to 10 cm to 25 cm Growth characteristics of Johnsongrass plants grown on rhizomes of adjacent lengths (differing by 5 cm) generally were not significantly different. Longer rhizomes (15, 20, or 25 cm) initiated new rhizome growth much earlier (about 20–30 days) than shorter rhizomes (2.5, 5, or 10 cm) Although all rhizome lengths showed a parallel growth potential, the lunger rhizomes were capable of more and faster growth, especially early after planting. It is suggested that Johnsongrass plants associated with longer rhizomes in the field as a result of limited tillage, coupled with their faster growth rate, are expected to interfere with crop production earlier than plants on shorter rhizomes unless controlled.     

Translocation of 14C-glyphosate in johnsongrass (Sorghum halepense L. Pers.) as affected by growth stage and rhizome length

Studies were conducted in the green house on ¹⁴C-methyllabelled glyphosate translocation in johnsongrass as affected by rhizome length and growth stage. The amount of ¹⁴C measured by the liquid scintillation technique in the rhizomes (2-8%) increased with rhizome length (10, 20 or 30 cm) and tended to increase with growth stage (15-30 cm tall, 45-60 cm tall, or at seedhead), but the amount of ¹⁴C per g fresh rhizome weight was almost similar in all cases. Of the total amount applied per plant (0·2 μCi) about 1/3 or less remained on the treated leaf area, while another 1/3 was a absorbed into the treated leaves. Autoradiographs showed that the ¹⁴C label moved to all plant parts, basipetally and acropetally. Migration du glyphosate ¹⁴ C chez le sorgho d'Alep (Sorghum halepense L. Pers.) en relation avec le stage de croissance et la longueur du rhizome Des recherches ont été effectuées en serru sur la migration du glyphosate marqué au ¹⁴C sur le méthyle, chez le sorgho d'Alep, en relation avec la longueur du rhizome et le stade de croissance. La quantité de ¹⁴C mesurée par la technique de scintillation liquide dans les rhizomes (2 à 8%) s'est accrue avec la longueur du rhizome (10, 20 ou 30 cm) et elle a eu tendance à augmenter avec le stade de croissance (Hauteur 15-30 cm, hauteur 45-60 cm ou épiaison), mais la quantité de ¹⁴C par gramme de poids frais de rhizome est restée Presque identique dans tous les cas. Environ 1/3, ou moins, de la quantitéà la surface des feuilles traitées par plante (0,2 μCi), est restéà la surface des feuilles traitées cependant qu'un autre 1/3 a été absorbé dans less feuilles traitées Les autoradiographies ont montré que le ¹⁴C marqueur a migré dans toutes les parties de la plante, dans le sens basipète et dans le sens acropète. Translokation von ¹⁴C-Glyphosat in Johnsongras (Sorghum halepense L. Pers.) in Abhängigkeit vom Wachstumsstadium der Pflanzen und der Rhizomlänge Im Gewächshaus wurden Versuche über die Translokation von ¹⁴C-Glyphosat in Johnsongras (Sorghum halepense L. Pers.) in Abhängigkeit vom Wachstumsstadium der Pflanzen und der Rhizomlänge durchgeführt. An den Rhizomen stieg der Gehalt von ¹⁴C(2–8%), gemessen mit der Flüssig-Szintillationstechnik, mit zunehmender Rhizomlänge (10, 20 oder 30 cm) an und nahm tendenziell auch mit fortschreitendem Pflanzenwachstum zu (15–30 cm und 45–60 cm Sprosslänge oder nach dem Rispenschieben); jedoch blieb die Menge pro g Rhizomfrischgewicht beinahe konstant. Von der insgesamt ausgebrachten Menge pro Pflanze (0.2 μCi) blieben bis zu 1/3 auf der behandelten Blättern absorbiert wurde. Die Autoradiographie zeigte, dass der ¹⁴C markierte Teil in alle Pflanzenteile sowohl basipetal wie auch akropetal transportiert wurde.     

Rhizome depth: the critical factor in winter survival of Sorghum halepense (L.) Pers. (Johnson grass)

Two biotypes of Sorghum halepense (L.) Pers., (Johnson grass) one which overwinters and one which does not overwinter from rhizomes at the northern limit of their North American ranges, were compared for rhizome production, rhizome survival and physiological tolerance to cold. The two biotypes differed in both the amount and depth of rhizome production under field conditions, with the non-overwintering biotype producing very few rhizomes 20 cm below the soil surface. Rhizome survival was clearly related to depth of burial for both biotypes. Survival was much reduced in the top 20 cm of soil and increased at greater depths to nearly 100% survival at depths of 40 to 50 cm. Differences in rhizome survival were apparent between the two biotypes and under the two climatic conditions tested, with greatly reduced survival of the overwintering biotype in the more extreme northern field plot. Similar levels of cold hardiness were observed in both hardened seedlings and rhizomes of the two biotypes. These levels were low and, in general, would not provide major protection against freezing temperatures. La profondeur des rhizomes; facteur critique de la siurvie hivernale de Sorghum halepense (L.) Pers. (Sorgho d'Alep) Deux biotypes de Sorghum halepense (L.) Pers. (Sorgho d'Alep), l'un capable et l'autre incapable d'hiverner à l'état de rhizomes à la limite septentrionale de leurs aires nord-américaines, ont été comparés pour leur production en rhizomes, la survie de ces rhizomes et la tolérance physiologique au froid. Les deux biotypes différaient à la fois par la quantité et le niveau de profondeur de leur production de rhizomes au champ :le biotype incapable d'hiverner produisait très peu de rhizomes à une profondeur de 20 cm. La survie des rhizomes était clairement reliée à la profondeur d'enfouissement pour les deux biotypes. La survie était réduite dans les premiers 20 cm de sol et augmentait avec la profondeur jusqu'à presque 100%à des profondeurs de 40 à 50 cm. Des différences de survie des rhizomes étaient apparentes entre les deux biotypes sous les deux conditions climatiques étudiées, le biotype capable d'hiverner présentant un taux de survie fortement réduit dans la parcelle expérimentale située le plus au Nord. Des niveaux similaires d'endurcissement au froid ont été observés dans des plantules et des rhizomes endurcis des deux biotypes. Ces niveaux étaient bas et en général ne fournissaient pas de protection majeure contre le gel. Tiefenlage der Rhizome: der kritische Faktor fur das Ueberleben von Sorghum halepense (L.) Pers. während des Winters Zwei Biotypen von Sorghum halepense (L.) Pers. von der nördlichen Grenze ihres Verbreitungsgebietes in N-Amerika wurden in Bezug auf Rhizomproduktion, Ueberleben ihrer Rhizome und physiologisch bedingte Kälteresistenz miteinander verglichen. Der eine der beiden Biotype überwintert nicht, der andere überwintert, d.h. reproduziert neues Wachstum aus den bestehen-den Rhizomen. Die beiden Typen zeigten unter Feldbedingungen Unterschiede in der Rhizom-bildung, sowohl bezüglich Menge und Tiefenlage der neubildung, wobei der nicht überwinternde Biotype sehr wenig Rhizome tiefer als 20 cm unter der Bodenorberfläche bildet. Das Ueberleben während des Winters war für beide Biotypen eindeutig mit der Tiefenlage der Rhizomasse korreliert. Die Uebelebensrate war in den obersten 20 cm sehr reduziert und nahm mit zunehmen der Tiefe bis zu fast 100% in 40–50 cm Tiefe zu. Es wurden eindeutige Unterschiede in der Ueberlebensrate zwischen den beiden Biotype unter den zwei untersuchten Klimabedingungen festgestellt, wobei ein stark verringertes Ueberle-benspotential des überwinternden Typs unter den extremeren nördlicheren Feldbedingungen beobachtet wurde. Abgehärtete Sämlinge und Rhizome beider Biotypen wiesen einen ähnlichen Grad von Kälteresistenz auf. Diese Resistenz war relativ gering und stellte in der Regel keinen genügenden Schutz gegen Frost dar.     

GROWTH,TUBER FORMATION AND SPREAD OF CYPERUS ROTUNDUS L. FROM SINGLE TUBERS*

Summary. Single tubers of Cyperus rotundus L. were planted at intervals over the year. Plant growth was slow and sprouting of tubers was inhibited at temperatures below 20°C, but tubers overwintered at temperatures above freezing point. In the warm season, plant growth and tuber formation rate closely followed air temperature and tubers were forming within 1 month from planting. No inflorescence appeared during the cool season. In autumn-planted C. rotundus grown in containers, the ratio of aerial to subterranean weight decreased from 1·1 in December to 0·2–0·4 in summer. The weight of tubers in mid-summer was about 10 times more than that present in December. Tubers formed at ail times of year and at various locations on plants sprouted readily in laboratory tests (76–100% sprouting). C. rotundus planted in March at wide spacings was grown in field conditions free of other plant competition for 20 months. Within 2 months the plants had spread to 90 cm. At the end of the first and the second summer of growth, the mean area of one plant was 7·6 m² and 56·7 m², respectively, and patches had expanded then by 2·8 m and 5·4 m, respectively, from the initial shoot. After 20 months of growth all tubers were present within the 0–40 cm soil depth, 60–70% of them in the 0–20 cm layer. About 30% of the tubers were within 1 m and 60% within 2 m of the plant centre. Under the patch centre there were about 1000 tubers per m² with 0·3 kg dry weight; in the upper 20 cm more than 3500 tubers weighing 0·9 kg were present per m³ of soil. Croissance, formation de tubercules et propagation de Cyperus rotundus L. issu de tubercules uniques     

Growth of Elymus repens (L.) Gould and Agrostis gigantea Roth. at different light intensities

Elymus repens (L.) Gould and Agrostis gigantea Roth. raised from rhizomes both responded to reduced light intensity by increased stem length, while the number of aerial shoots was reduced. The weight of the aerial parts was not influenced by a 50% reduction of the daylight intensity, but a further reduction of light caused a significant decrease in weight. The production of new rhizomes was more influenced by shading than were the aerial shoots. The consequence was an increase in the shoot/rhizome ratio. The food reserve per bud measured as inter-node weight in E. repens and A. gigantea was reduced only with intensive shading, and the vitality of the rhizomes appeared independent of light intensity. Intensive shading in early as compared to late summer caused a reduction in the number and weight of aerial shoots, but not in the weight of new rhizomes. Light intensities equal to those found in a spring wheat crop allowed more E. repens growth than light intensities equal to those in a spring oat crop. E. repens raised from seeds and grown at light intensities equal to those found in a cereal crop, showed insignificant rhizome production.     

DEVELOPMENT OF CYNODON DACTYLON (L.) PERS.*

Summary. Early development of Cynodon dactylon (L.) Pers, was studied on one-node rhizome fragments planted at successive dates over a year. Aerial growth followed the changes in external temperature; in the cool season tops grew very slowly but remained alive. New rhizomes were formed only at temperatures exceeding 15–20°C. Flowering occurred in the warm season from May onwards. No relationship was found between flowering and rhizome formation. The age of plants forming new rhizomes decreased from 5 months for the January planting to less than 2 months for the May-September plantings. Rhizome bud germination was maximal between 23 and 35°C, slow below 20°C and inhibited at 10°C. The weight ratio of tops to subterranean parts of established plants was near 1 in winter, declined in March-April and remained at 0·5–0·6 from May onwards. An established sward of C. dactylon was sampled from September to November of the following year. Dry weight was lowest from January to mid-April, rose in spring and decreased in late summer. Almost no rhizomes were found deeper than 45 cm. Underground parts from the 0–15, 15–30 and 30–45 cm horizons constituted 62, 26 and 12% of the total weight, respectively; rhizomes formed more than 90% of the total underground dry weight. In the warm season the dry weight of the subterranean organs amounted to 2, 0·7 and 0·4 kg/m³ of soil in the three horizons, respectively. Percent dry matter in tops and subterranean parts was about 35–45% in the winter and 50–65% in the warm season. Up to 2% reducing sugars was found in various parts of the plants. The water-soluble sugar content of rhizomes was high in November-December, decreased in late winter, rose again in spring, and decreased in late summer. Percent germination of rhizome buds fluctuated greatly during the year, but complete dormancy was never recorded. Newly-formed rhizomes showed a high germinative capacity. Similar germination percentages were found on fragments with one node and those with several nodes. Développement du Cynodon dactylon (L.) Pers.     

Regeneration of yarrow (Achillea millefolium L.) rhizome fragments of different length from various depths in the soil

The regenerative response of the rhizomes of Achillea millefolium L. to fragmentation and burial was studied in field experiments on three different soils. The percentage of buds producing shoots (estimated from surviving rhizome fragments) from 4 cm (1·6 nodes), 8 cm (3·8 nodes) and 16 cm (6·7 nodes) rhizome fragments was 63, 44 and 32 respectively averaged over all soils and depths of 5, 10 and 15 cm. The depth at which 50% of the fragments failed to produce an emerged shoot (LD₅₀ depth) was 9·3, 12·4 and 17·9 cm for 4-, 8- and 16-cm fragments respectively averaged over all soils. No fragments survived on the soil surface. The time of emergence of the first shoots was delayed and the rate of emergence and ultimate shoot population reduced with increasing depth of burial. Dry-matter production by aerial shoots and new rhizomes decreased linearly with depth of burial of the rhizome fragments. Soil type had no effect on the regeneration of the fragments. The significance of the results for the control of A. millefolium is discussed.     

PHYSIOLOGICAL EFFECTS OF DALAPON IN CYNODON DACTYLON (L.) PERS.*

Summary. Studies on the physiological effects of dalapon in Cynodon dactylon (L.) Pers. were carried out. Field and glasshouse experiments showed that dalapon is freely translocated in the aerial organs and from these to the rhizomes. No transformation of the herbicide was detected during 72 h following application. In rhizomes as well as in stolons, dalapon caused growth inhibition and necrosis of buds while root growth was apparently not affected. This differential susceptibility was confirmed by culturing node explants in nutrient solution containing dalapon. Although dalapon killed aerial organs, most rhizomes were capable of recovery even when a high dose was applied. These results are discussed. Effets physiologiqius du dalapon sur Cynodon dactylon (L.) Pers.     

Fate of glyphosate in Agropyron repens (L.) Beauv. growing under low temperature conditions

Absorption, translocation and distribution of ¹⁴C-glyphosate were examined in Agropyron repens (L.) Beauv. plants growing under field conditions in the autumn. Glyphosate absorption did not increase beyond 3 days after application, whereas translocation to the rhizomes continued up to 7 days after application. The translocated glyphosate accumulated more in new rhizomes than in older parts of the rhizomes. Ten per cent of the glyphosate translocated out of the treated shoot was recovered in younger shoots 7 days after application. Plants harvested the following spring contained less than 20% of the glyphosate originally applied. Although a growth cabinet experiment indicated that 34% of the glyphosate in the rhizomes of treated plants could be remobi-lized into new aerial shoots, considerably less was recovered in new, aerial shoots in the spring in the field-grown plants. Freezing experiments showed that glyphosate translocation to the rhizomes was only prevented when cold treatment caused visible damage to A. repens foliage.     

Effect of 2-chloroethylphosphonic acid on the morphology and apical dominance of Agropyron repens

2-Chloroethylphosphonic acid applied to foliage or soil released dormant buds from apical dominance in aerial shoots and rhizomes of Agropyron repens. The aerial shoots had scale-like leaves and shortened internodes with adventitious roots at the nodes. The treated plants had a dwarf appearance and had increased peroxidase activity.     

Control of Sorghum halepense (L.) Pers. in cotton with post-emergence herbicides and trifluralin

A field experiment was conducted in 1981 and 1982 to evaluate five post-emergence herbicides applied alone or following a preplant incorporated application of trifluralin for the control of Sorghum halepense (L.) Pers. in cotton (Gossypium hirsutum). One application of the methyl ester of haloxyfop [methyl 2- (4- ((3-chloro-5-trifluoromethyl)-2-pyridinyl)oxy)phenoxy)pro-panoate], trifluralin plus the ethyl ester of DPX-Y6202 [ethyl[2-[-4-(6-chloro-2-quinoxalinyl)oxy]phenoxy]propionate], the butyl ester of fluazifop and trifluralin plus haloxyfop resulted in over 90% control of S. halepense just prior to harvest in 1981 and 1982. Sorghum halepense control was similar whether the post-emergence herbicides were applied alone or following preplant incorporated trifluralin at 0.8 kg ha^?1. La lutte contre Sorghum halepense (L.) Pers. en culture de cotonnier moyennant des herbicides de post-levée et la trifluraline Une expérience a été installée en plein champ en 1981 et 1982 dans le but d'évaluer cinq herbicides de post-levée, appliqués seuls ou suite à la trifluraline incorporée avant le semis, dans la lutte contre Sorghum halepense (L.) Pers. en culture de cotonnier (Gossypium hirsutum). Une seule application de l'haloxyfop ester de méthyle [méthyle 2-(4-((3-chloro-5- (trifluorométhyle)-2-pyridinyle) oxy)phénoxy)propanoate], de trifluraline + DPX-Y6202 ester d'éthyle (éthyle[2-[4-(6-chloro-2-quinoxalinyle)oxy]phénoxy)propionate), de l'ester butylique du fluazifop et de trifluraline + haloxyfop a permis en 1981 et 1982 une bonne maîtrise (90%) de S. halepense juste avant la récolte. La maîtrise de Sorghum halepenseétait semblable, que les herbicides de postlevée aient été précédés ou non d'une application de trifluraline à 0,8 kg ha^?1 incorporée avant le semis. Bekämpfung von Sorghum halepense (L.) Pers. in Baumwolle mit Nachauflaufherbiziden und Trifluralin In den Jahren 1981 und 1982 wurden Feldversuche zur Bekämpfung von Sorghum halepense (L.) Pers. in Baumwolle (Gossypium hirsutum) mit fünf Nachauflaufherbiziden durchgeführt. Die Herbizide wurden allein oder nach einer vor der Baumwollsaat erfolgten Einarbeitung von Trifluralin appliziert. Eine Applikation des Methylesters von Haloxyfop [Methyl-2-(4-((3-chloro-5-(trifluormethyl)-2-pyridinyl)oxy)phenoxy)propanoat]. Von Trifluralin + Aethylester von DPX-Y 6202 [Aethyl[2-[-4-(6-chlor-2-quinoxalinyl)oxy)phenoxy)propionat], des Butylesters von Fluazifop und Trifluralin + Haloxyfop ergaben in beiden Jahren kurz vor der Ernte eine über 90 ige Kontrolle von S. halepense. Der Bekämpfungserfolg war ähnlich, gleichgültig ob die Herbizide allein oder nach der Einarbeitung von Trifluralin (0,8 kg ha^?1) appliziert worden waren.     

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     

Can the riparian invader,Arundo donax,benefit from clonal integration?

Resource sharing through rhizomes of clonal plants supplements locally available nutrients to enhance recruitment and growth in resource‐limited environments. We investigated whether Arundo donax, an invasive clonal plant, can benefit from clonal integration. Sharing resources between ramets can facilitate resprouting from mowing, fire and herbicide treatments, but it is unknown whether clonal integration contributes to A. donax invasion success. Our first objective was to determine whether A. donax rhizomes transported water between ramets. Hydrogen isotopic–enriched water was applied on three 1 m diameter areas, and rhizome and soil samples were collected beyond the watering zone after 5, 24 and 48 h of the last watering. Logistic modelling indicated that water was able to move laterally at least 3.5 m. The second objective was to determine whether clonal integration enhanced growth and survival of A. donax ramets. We compared growth‐related responses in paired 1 m² plots with severed and intact rhizomes. In the first 19 days, rhizome severing nearly doubled ramet density, while by 77 days, the intact rhizomes produced 67% taller stems with 49% greater diameter and showed higher survival rate after flooding. This study provides initial evidence that physiological integration could be an important mechanism in A. donax, which can enhance its competitive abilities, accelerate rates of encroachment and strengthen its capability to recolonise disturbed areas. Our results highlight an important consideration of clonal invasive species in weed management.     

The effect of temperature on sprouting and early establishment of Cynodon dactylon

Bud-sprouting dynamics, sprouting base temperature and reserve mobilization of rhizomes and stolons of Cynodon dactylon (L.) Pers. were characterized in a laboratory experiment under dark conditions. In addition, the dynamics of sprout emergence were determined during 2 years under field conditions. In the laboratory experiment, buds from the vegetative structures did not sprout at temperatures below 7^C. The rate of sprouting increased with temperature within the range 11–33^C, and a base temperature of 7.71^C was determined for bud sprouting of rhizome and stolons of the weed. An exponential model is proposed relating the percentage of sprout emergence in the field to accumulated thermal units, calculated as the sum of the daily mean air temperature above the base temperature of bud sprouting. This model satisfactorily predicted the dynamics of C. dactylon sprout emergence in sunflower (Helianthus annuus L.) crop fields. The efficiency of carbohydrate reserve use during sprout growth was highly dependent on temperature and type of vegetative structure The efficiency was maximum at 20^C and was higher for rhizomes than for stolons. The main factors influencing bud sprouting and early weed establishment are discussed.     

Preliminary studies on two Diaspididae (Hemiptera) species feeding on Johnsongrass (<Emphasis Type="BoldItalic">Sorghum halepense</Emphasis>) in Turkey

The scale insects Acanthomytilus sacchari (Hall) and Duplachionaspis erianthi Borchsenius (Hemiptera, Diaspididae) are newly recorded as indigenous insects from Turkey. Both A. sacchari and D. erianthi were found to feed only on rhizomes of Johnsongrass. A field study was conducted to determine host ranges and feeding effects of these scale insects on Johnsongrass, Sorghum halepense (L.) Pers. No feeding of these species was observed on Zea mays L. (maize), Sorghum sudanense Staph. (sorghum), Aegilops triuncialis L. (barbed goatgrass), Avena fatua L. (wild oat), A. sterilis (sterile oat), Bromus tectorum L. (downy brome), Cynodon dactylon (L.) Pers. (bermudagrass), Phragmites australis (Cav.) Trin. ex Steudel (common reed), Poa bulbosa L. (bulbous bluegrass), or Secale montanum Guss. (wild rye). The mean infestation rates of the scale insects on Johnsongrass in southeastern Anatolia were 11.47% and 1.64% for A. sacchari and D. erianthi, respectively. Further investigations are required to clarify their biology and damage to Johnsongrass under field conditions.     

Sorghum halepense (L.) Pers. control with foliar-applied herbicides in conventional and no-tillage soyabeans*

Separate field experiments were conducted to evaluate Sorghum halepense (L.) Pers. (johnson-grass) control with foliar-applied herbicides in soyabeans (Glycine max (L.) Merr. cv. Williams) grown in tilled (mould board plough) or no-tillage fields. Fluazifop-butyl, sethoxydim, CGA-82725 and mefluidide were applied post-emergence to 45-cm high S. halepense and glyphosate was applied with a wick bar to 90-cm high S. halepense in the conventional and no-tillage studies. HOE-00581 {ethyl 2-[4-[(6-chloro-2-benzoazolyl)oxyl]-phenoxy]propanoate} was applied to 45-cm high S. halepense only in the no-tillage studies. Fluazifop-butyl, sethoxydim, CGA-82725, HOE-00581 (no-tillage only) and glyphosate provided good control of S. halepense in conventional and no-tillage soyabeans and generally increased soyabean yields compared to weedy controls, when low precipitation was not limiting yields. Mefluidide at 0.3 kg ai ha^?1 provided the least S. halepense control in the conventional and no-tillage studies. The studies were not designed to compare S. halepense control in the two tillage systems; however, these data show that tillage to disrupt S. halepense rhizomes was not required to obtain good control of S. halepense with foliar applications of fluazifop-butyl, sethoxydim, CGA-82725, HOE-00581 and glyphosate. La lutte contre Sorghum halepense (L.) Pers. utilisant des herbicides foliaires dans le soja en culture classique et en non-culture Plusieurs essais ont été installés sur le terrain dans le but d'évaluer des herbicides foliaires pour la destruction de Sorghum halepense (L.) Pers. dans le soja (Glycine max (L.) Merr. var. Williams) cultivé en terre labourée et en non-culture. Le fluazifop-butyle, le séthoxydime, le CGA-82725 et le méfluidide ont été appliqués en postlevée sur S. halepense haut de 45 cm et le glyphosate a été appliqué sur S. halepense haut de 90 cm, utilisant un frotteur, dans les deux sytèmes de culture. HOE-00581 (éthyle 2-[4-[(6-chloro-2-benzoazolyl)oxyl]phénoxy]propanoate) a été appliqué sur S. halepense haut de 45 cm uniquement dans les systèmes de·non-culture. Le fluazifop-butyle, le séthoxydime, le CGA-82725, le HOE-00581 et le glyphosate ont bien maitriséS. halepense dans les deux systèmes de culture du soja, tout en augmentant les rendements de soja par rapport au témoin enherbé, là où une précipitation insuffisante n'est pas intervenue. Le méfluidide à 0,3 kg ai ha^?1 a donné la plus faible destruction de S. halepense en culture classique et en non-culture. Une comparaison de la destruction de S. halepense dans les deux systèmes de culture n'était pas le but principal de ces travaux; cependant ces données font voir qu'un labourage pour briser les rhizomes de S. halepense n'est pas de rigueur pour obtenir une bonne maîtrise de l'adventice par des applications foliaires de fluazifop-butyle, séthoxydime, CGA-82725, HOE-00581 et glyphosate. Sorghum halepense (L.) Pers. Bekämpfung mit blattwirksamen Herbiziden in Soyakulturen mit und ohne Bodenbearbeitung Es wurden separate Feldversuche zur Bekämpfung von Sorghum halepense (L.) Pers. mit blattwirksamen Herbiziden in Soyakulturen (Glycinemax (L.) Merr. cv. Williams), ohne und mit Bodenbearbeitung (Mouldboard Pflug), ausgeführt. Fluazifop-Butyl, Sethoxydim, CGA-82725 und Mefluidid wurden postemergent auf 45 cm hohe und Glyphosat mit einem Docht-Streichgerät (wick bar) auf 90 cm hohe S. halepense appliziert; diese Produkte kamen in den Feldern mit und ohne Bodenbearbeitung zur Anwendung. HOE-00581 {Aethyl 2-[4-[(6-chlor-2-benzoazolyl)oxyl]phenoxy]propanoat} wurde nur auf den Parzellen ohne Bodenbearbeitung auf 45 cm hohe S. halepense appliziert. Fluazifop-Butyl, Sethoxydim, CGA-82725, HOE-00581 (Ohne Bodenbearbeitung) und Glyphosat erzielten in bearbeiteten und unbearbeiteten Feldern eine gute Bekämpfung von S. halepense und bewirkten im allgemeinen eine Erhöhung der Ernteerträge, sofern nicht geringe Niederschläge als limitierender Faktor auftraten. Mefluidid (0,3 kg ai ha^?1) ergab die geringste Wirkung in bearbeiteten und unbearbeiteten Feldern. Diese Versuche waren nicht geplant um den Erfolg der S. halepense Bekämpfung unter den zwei Anbaubedingungen (mit resp. ohne Bodenbearbeitung) miteinander zu vergleichen; immerhin zeigen die Ergebnisse, dass eine Bodenbearbeitung zur Zerkleinerung der S. halepense-Rhizome nicht notwendig ist, um gute Effekte mit Fluazifop-Butyl, Sethoydim, CGA-82725, HOE-00581 und Glyphosat zuerzielen.     

Seasonal variation in sprouting capacity from intact rhizome systems of three perennial weeds

The three rhizomatous perennials Elytrigia repens, Equisetum arvense and Tussilago farfara are all problematic in Scandinavian agriculture, due to their low susceptibility to soil cultivation. While repeated soil tillage is a fundamental part of the integrated control of these species, it is highly energy consuming and inefficient during periods when little sprout regrowth occurs. Substituting cultivation with mowing will reduce the environmental impact and labour costs, but its efficiency will still depend on the capacity of plants to sprout. Therefore, we studied the seasonal pattern in emergence and rhizome biomass allocation from July to April in six populations for each of the species. Plants were grown outdoors in pots buried in soil and exhumed at regular intervals in a two‐year experiment. In all three species, biomass allocation to rhizomes continued until late in the autumn. Emergence was severely impaired in E. arvense and T. farfara in September–October, while in E. repens, there was no such reduction in the number of emerged shoots. However, in the latter species, the shoot/rhizome ratio decreased and remained low until the plants had been exposed to a period of low temperatures. The increase in shoot/rhizome ratio for E. repens coincided with the resumed capacity to emerge for E. arvense and T. farfara. These results imply that there is no need to repeat a defoliation of E. arvense and T. farfara, if carried out in September–October. However, removal of the aerial plant parts early in the autumn is important to interrupt the upload of storage compounds to the rhizome systems of all species.     

Rhizome-induction activity of chiral 2-α-methylbenzylamino-4-alkylamino-6-chloro-1, 3, 5-triazines in Cyperus serotinus Rottb.

A cytokinin-like effect of chiral 2-α-methylbenzylamino-4-alkylamino-6-chloro-1,3,5-triazines was found using a rhizome-inducing assay with Cyperus serotinus Rottb. tubers. C. serotinus tubers germinated in distilled water yielded plantlets with roots and leaves. Secondary rhizomes were normally not observed within the regular 14-day incubation time in water culture, whereas after increasing incubation periods a very short rhizome appeared (controls). 6-Benzylaminopurine (BA) significantly stimulated rhizome induction, while other plant hormones were inactive. The (R)-isomers of the 1, 3, 5-triazine compounds also stimulated induction of the rhizomes, whereas the (S)-isomers did not. The described rhizome induction system seems to be suitable as a cytokinin bioassay. The (R)-1, 3, 5-triazine compounds showing rhizome-inducing activity (RI activity) inhibited root formation and plant growth at high concentrations with symptoms which were very similar to those of BA. Therefore, the (R)-isomers appear to act as cytokinins in the rhizome induction assay.