Inhibition of Echinochloa crus-galli var. frumentacea seedling root elongation by chiral 1, 3, 5-triazines in the dark

2-z-Substituted benzylamino-4-substituted-amino-6-chloro-1,3, 5-triazines are herbicidal compounds showing leaf-burning and/or growth inhibition with concomitant greening and stunting. Effects of chiral 1,3,5-triazine compounds in a light-independent seedling root elongation test with Echinochloa crus-galli var. frumentacea Wight demonstrated an interaction between chirality and root growth inhibition. The test compounds inhibited root growth, and this inhibition was due to interference with a system or systems other than photosynthesis. 4-(R)-sec-butylamino-2-(α,α-dimethylbenzyl)amino-6-chloro-1,3, 5-triazine showed the highest inhibitory activity, and 4-methylamino-2-(R)-a-methylbenzylamino-6-chloro-1,3,5-triazine was second. The chiral requirement for a strong inhibition of root growth was the (R)-configuration, contrasting with the requirement for the (S)-configuration for an inhibition of photosystem II.     

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.     

乙烯利对草甘磷在空心莲子草中传导及生物活性的影响

在人工气候室培养空心莲子草,植株经草甘膦与乙烯利混合处理后,测定对植株的抑制作用和草甘膦的吸收与传导量。结果表明,加入乙烯利(100mg·L~(-1))后草甘膦(300mg·L~(-1))对地下根茎抑制率比对照提高了13.6个百分点。植株经乙烯利喷雾处理后,基芽、地下茎和根系中~(14)C-草甘膦含量分别是对照的3.56、1.75和2.35倍。放射性成像图显示,植株地下茎与根系中~(14)C-草甘膦传导量明显高于对照。     

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.     

Involvement of cytochrome P‐450 enzyme activity in the selectivity and safening action of pyrazosulfuron‐ethyl

To investigate the selectivity and safening action of the sulfonylurea herbicide pyrazosulfuron‐ethyl (PSE), pyrazosulfuron‐ethyl O‐demethylase (PSEOD) activity involving oxidative metabolism by cytochrome P‐450 was studied in rice (Oryza sativa L cv Nipponbare) and Cyperus serotinus Rottb. Cytochrome P‐450‐dependent activity was demonstrated by the use of the inducers 1,8‐naphthalic anhydride and ethanol, the herbicides PSE, bensulfuron‐methyl, dimepiperate and dymron, or the inhibitor piperonyl butoxide (PBO). Growth inhibition in C serotinus seedlings was more severe than that in rice seedlings. O‐Dealkylation activities of PSE were induced differently in rice and in C serotinus, with distinctly higher activity in rice seedlings. The induced PSEOD activities were slightly inhibited by PBO in rice seedlings, whereas they were strongly inhibited in C serotinus seedlings. Dimepiperate and dymron were effective safeners of rice against PSE treatment. Treatments with herbicide alone resulted in less induction of PSEOD activity compared with combined treatments of the herbicide and safener. PSEOD activity in rice seedlings induced with herbicide alone was strongly inhibited by PBO, whereas it was weakly inhibited in rice seedlings induced with combinations of PSE and two safeners. These results suggest that O‐demethylation by cytochrome P‐450 enzymes may be involved in the metabolism of PSE and may contribute to its selectivity and safening action. Furthermore, these results suggest the existence of a multiple form of cytochrome P‐450 in plants. © 2001 Society of Chemical Industry     

Regenerative capacity of rhizomes and tubers from two populations of Helianthus tuberosus L. (Jerusalem artichoke)

The regenerative responses of rhizomes and tubers from two populations of Helianthus tuberosus L. to burial and fragmentation were studied in field experiments. The regeneration of both populations varied with planting depth and stage of growth at which fragmentation occurred. Shoots of both populations emerged from rhizomes or tubers planted to depths of 30 cm. The percentage of tubers that regenerated was higher than that of rhizomes, particularly from deeper planting depths. The regeneration from rhizomes and tubers of a riverbank population was greater than that of a‘weedy’population. Rhizomes and tubers from both populations that had failed to produce shoots I year after planting were found to have decomposed completely. The significance of these results in relation to the distribution and control of H. tuberosus is discussed.     

Interaction between optical isomerism and plant pharmacological action,change of modes of action and chirality of 1-(α-methylbenzyl)-3-p-tolylurea

The optical isomers, (R)-1(α-methylbenzyl)-3-p-tolylurea ((R)-MBU) and (S)-1-(α-methylbenzyl)-3-p-tolylurea ((S)MBU), which are analogues of daimuron [1-(α,α-dimethylbenzyl)-3-p-tolylurea], a herbicide for Cyperaceae weeds and a safener for paddy rice, exhibited different biological responses. These two physiological properties of daimuron were observed separately in (R)-MBU and (S)-MBU. Only (R)-MBU had herbicidal activity against Cyperaceae weeds, while the (S)-isomer was a more effective safener against bensulfuron-methyl (BSM) injury of rice seedlings than was (R)-MBU. (S)-MBU promoted root growth of rice seedlings, but the (R)-enantiomer inhibited root growth. (S)-MBU was a more potent inhibitor than (R)-MBU on PS II reaction of spinach broken chloroplasts. Furthermore, (S)-MBU and (R)-MBU showed cross intergenus selective phytotoxicity among the Gramineae plants, Oryza sativa L. (rice, cv. Tsukinohikari, japonica), Triticum aestivum L. (wheat, cv. Norin No. 61) and Echinochloa crusgalli var. frumentacea Wight, on root growth inhibition in the dark.     

SPATIAL GROWTH OF SORGHUM HALEPENSE (L.) PERS.*

Summary. Small plants of Sorghum halepense (L.) Pers. were planted in the field and grown without competition from weeds and crops for 2½ years. The plant spread by means of subterranean rhizomes from which aerial shoots developed at increasing distances from the plant centre, and by tillering around these aerial shoots to form clumps. No preferential direction of expansion was detected and established patches developed an approximately circular shape. Aerial growth stopped completely in the cold season. During the warm season the mean area increment amounted to 1·3 m²/month and was similar in both years of observations. After 2½ years of growth, patches had extended up to 3·4 m from the initial sprig and had a mean area of 17 m². In the second summer of growth, shoot density reached 190/m² and mean seed production was 84 g, or 28 000 seeds per plant. About 80% of rhizome dry weight was present in the upper 20 cm of soil and rhizomes did not penetrate deeper than 40 cm. About 80% of rhizome dry weight was present within 1 m radius from the plant centre. Croissance dans l'espace de Sorghum halepense (L.) Pers.     

Suppression of Food Intake in Triatoma infestans by N-Substituted Methyl Maleamates

A series of methyl esters of N-substituted (Z)- and (E)-maleamic acids were synthesized and their effect on food intake measured on fifth-instar nymphs of Triatoma infestans. Suppression of food intake was found only for the (Z)-isomers. The initial reaction rate of the synthesized compounds with glutathione (GSH) was calculated from the reaction in vitro of the (Z)-isomers. No reaction was observed with the (E)-isomers. Good correlation between the suppression of food intake, measured by its ED₅₀ (effective dose that inhibited feeding of 50% of the population) and the initial reaction rate with GSH and the hydrophobic parameter π, was found. © of SCI.     

Studies in the growth of Pteridium aquilinum (L.) Kuhn. (bracken) 1. Regeneration of rhizome segments

The patterns of regeneration of Pteridium aquilinum (L.) Kuhn. (bracken) rhizome segments grown in pot culture are described. The overall capacity for regeneration was unaffected by the rhizome type planted, i.e., whether it consisted of only a length of frond-bearing ‘short shoote’ or whether this was attached to part of the main storage and exploratory ‘long shoot’. In all cases rhizomes extended, produced new lateral buds and developed fronds during the first summer. Regenerative capacity was also similar for segments with or without apical buds. Different patterns of growth were observed in plants grown from different types of segment: in particular, more new lateral buds were produced on rhizome segments originally lacking an apex. As rhizomes extended, the distance between successive lateral buds increased. The results are discussed in relation to the possible roles of correlative inhibition and patterns of translocation between fronds and rhizomes and to information on field populations.     

Spray Application in Plantation Crops

Abstract

The effects of intraspecific competition on the growth, development and resource‐allocation of Panicum repens was studied under greenhouse conditions. Evidence of severe intraspecific competition and adjustments to plant growth as a response to stress caused by competition, was seen from fairly early stages. An eight‐fold difference in initial plant density per pot, did not produce a significant difference in the dry weight accumulation between densities by 16‐weeks. Increase in plant density resulted in a very significant decrease in dry weight accumulation on a per plant basis, as expected. In general, dry weight partitioning into rhizomes and inflorescences increased with time at all densities, with a concomitant decrease in the percent dry weight partitioned into roots and shoots. Under low density conditions more dry weight was partitioned into inflorescences than at higher densities, indicating a shift in resource‐allocation with changing density. However, the expected shift of dry weight partitioning towards rhizome production at the highest densities was not evident. Allocation of resources to rhizomes did not vary with density. Even the lowest density plants which were not subjected to competitive stress, and the plants at the highest density, all allocated about one fifth of their dry weights to rhizomes. Plants under the highest density stress showed a very significant reduction in the number of tillers they produced and tiller dry weights, on both per pot and per plant basis. The study provides several insights into the highly adaptive and competitive nature of the grass weed, which contribute greatly to its success as a species.     

Studies on the depth distribution and on the germination and growth of Equisetum arvense L (field horsetail) from tubers

Soil core samples taken from a sandy loam soil at Woburn during January 1972, following spring beans during the previous year, indicated that half the rhizome dry weight of Equisetum arvense (L.) occurred in the uppermost 25 cm of soil and 10% between 75 and 100 cm. Tubers occurred relatively more deeply with half the number and three-quarters of the weight deeper than 50 cm. However, after a 2-year fallow 80% of the rhizomes and tubers were in the uppermost 25 cm of soil. In general, the weight of individual tubers increased with increasing depth in the soil. In pots in the glasshouse, tubers that were formed in one season lost weight when new shoots emerged in the following year; those formed during summer germinated readily in warmth indoors when detached in the autumn, but not until June of the following year in the field. Burial of tubers at a range of depths down to 25 cm did not affect the number of shoots emerging but emergence was delayed. Plants made more growth in neutral than in acid or basic soil, more in silty clay loam than in sandy loam and appeared well adapted to growth in soils with little nitrogen. In general, rhizome growth was less affected by variations in pH and nitrogen level than were shoots and tubers. Plants grown from tubers were suppressed greatly by wheat sown densely and given a moderate amount of nitrogen fertilizer but had negligible effect on the wheat. With fewer wheat plants given less nitrogen, the species partitioned more of its assimilate into tubers than when it was grown alone. The significance of tubers in the biology of the species is briefly discussed and areas meriting further study are highlighted.     

Colonization and infestation ability of Bolboschoenus maritimus Palla in rice paddies of the Camargue,France

Bolboschoenus maritimus is one of the major weed constraints for irrigated rice‐cropping systems in the Camargue, France. This perennial plant propagates mainly through the production of numerous tubers. Observations in both controlled conditions and on‐field studies were used to enhance the level of knowledge of the biology, functioning and infestation dynamics of B. maritimus, with a view to rationalize weed control practices. It was found that B. maritimus displayed a great potential to produce a large number of shoots, rhizomes and tubers. Its propagation in the field plots depended on the initial weed density and its spatial colonization did not show any preferred direction (isotropic). Further observations that were made in the paddy fields showed an interaction between the different cultural practices that were tested and the infestation dynamics of B. maritimus. Efficient control of B. maritimus infestation in the field should make use of the data reported here, based on three levels: (i) prevention of weed stem proliferation during the cropping season with specific herbicides; (ii) elimination of the tubers after the rice crop; and (iii) reduction of the tuber‐germinating ability.     

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.     

The biology of African feather grass (Pennisetum macrourum Trin.) in Tasmania, II. Rhizome biology

The rhizome biology of Pennisetum macrourum was studied in a series of field and glasshouse experiments. The total available carbohydrate content of rhizomes remained between 15 and 22% of dry weight throughout the year, with fluctuations, related to the seasonal growth pattern. The percentage regeneration or rhizome fragments of one, two and four nodes buried at 15 cm was 13, 33 and 57, respectively. Thirty percent of 4-node rhizome fragments regenerated from a depth of 25 cm. In 11 desiecation experiment, regeneration of 3-node rhizome fragments occurred until rhizome moisture content was reduced to 14%, The time taken to reach this moisture content varied from 4 to 10 days depending on the temperature. The significance of these results for the control of P. macrourum is discussed.     

Control of Elymus repens by rhizome fragmentation and repeated mowing in a newly established white clover sward

Control of perennial weeds, such as Elymus repens, generally requires herbicides or intensive tillage. Alternative methods, such as mowing and competition from subsidiary crops, provide less efficient control. Fragmenting the rhizomes, with minimal soil disturbance and damage to the main crop, could potentially increase the efficacy and consistency of such control methods. This study's aim was to investigate whether fragmenting the rhizomes and mowing enhance the control of E. repens in a white clover sward. Six field experiments were conducted in 2012 and 2013 in Uppsala, Sweden, and Ås, Norway. The effect of cutting slits in the soil using a flat spade in a 10 × 10 cm or 20 × 20 cm grid and the effect of repeated mowing were investigated. Treatments were performed either during summer in a spring‐sown white clover sward (three experiments) or during autumn, post‐cereal harvest, in an under‐sown white clover sward (three experiments). When performed in autumn, rhizome fragmentation and mowing reduced E. repens shoot biomass, but not rhizome biomass or shoot number. In contrast, when performed in early summer, rhizome fragmentation also reduced the E. repens rhizome biomass by up to 60%, and repeated mowing reduced it by up to 95%. The combination of the two factors appeared to be additive. Seasonal differences in treatment effects may be due to rhizomes having fewer stored resources in spring than in early autumn. We conclude that rhizome fragmentation in a growing white clover sward could reduce the amount of E. repens rhizomes and that repeated mowing is an effective control method, but that great seasonal variation exists.     

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.     

Vascular blackening of wasabi rhizomes caused by <Emphasis Type="Italic">Pectobacterium carotovorum</Emphasis> subsp. <Emphasis Type="Italic">carotovorum</Emphasis>

Wasabi (Wasabia japonica) is grown for its highly-valued rhizome which is used as a condiment in Japanese food. Symptoms of vascular blackening in the rhizome were first observed in 2005 in plants grown in British Columbia, Canada. Microscopic observations and microbial isolation from infected tissues revealed that most of the xylem tracheid cells were blackened and bacteria were consistently associated with symptomatic plants. The bacterium most frequently recovered was identified as Pectobacterium carotovorum subsp. carotovorum (Pcc) using BioLog™ and sequencing of a specific ~510 bp IGS region. Pathogen-free plants obtained using meristem-tip micropropagation were inoculated with a wasabi isolate of Pcc. Vascular blackening symptoms developed in the rhizome after 8 weeks when the rhizome was first wounded by stabbing or cutting, or if the roots were pre-inoculated with Pythium species isolated from rhizome epidermal tissues, followed by inoculation with Pcc at 1 × 10⁸ cells ml⁻¹. Xylem tracheid cells were blackened and Pcc was reisolated from all diseased tissues. The highest frequency of rhizome vascular blackening occurred at 22°C and 27°C and these tissues occasionally succumbed to soft rot at higher temperatures, but not when inoculated tissues were incubated at 10°C. The rooting medium used by growers for vegetative propagation of wasabi was shown to contain Pcc but the pathogen was not recovered from the irrigation water. Entry of Pcc through wounds on wasabi rhizomes and the host tissue response result in symptoms of vascular blackening.     

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.     

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.