Growth characteristics,nutrient allocation and photosynthesis ofCarex species from floating fens

Summary The purpose of this study was to investigate various growth parameters, dry matter and nitrogen, phosphorus and potassium allocation and photosynthesis ofCarex acutiformis, C. rostrata andC. diandra growing in fens with, in this order, decreasing nutrient availability and decreasing aboveground productivity. Plants were grown from cuttings at optimum nutrient conditions in a growth chamber. Growth analysis at sequential harvests revealed that the species had no inherently different relative growth rates which could explain their different productivity, but that their LAR (LWR and SLA) decreased in the orderC. acutiformis, C. rostrata, C. diandra and their NAR increased in this order. All growth parameters decreased during plant growth even under the controlled conditions of the experiment.C. acutiformis allocated relatively much dry matter to the leaves,C. rostrata to the rhizomes andC. diandra to the roots. This may, in part, explain the higher aboveground biomass production ofC. acutiformis in the field. Nitrogen, but not phosphorus and potassium, allocation patterns were different for the three species.C. diandra, the species from the nitrogen-poorest site, had the highest leaf N content of the three species and also a higher chlorophyll content. Related to this, this species had the highest photosynthetic activity of whole plants both when collected from the field and when grown in the growth chamber. The nitrogen productivity was similar for the three species and the photosynthetic nitrogen use efficiency, determined forC. acutiformis andC. diandra, was similar for these two species.C. diandra had the most finely branched root system, i.e., the highest specific root length of the three species and its root surface area to leaf surface area ratio was also the highest. All three species showed higher nitrate reductase activity in the leaves than in the roots when grown on nutrient solution. The growth ofC. diandra at a relatively nutrient-poor site and a rather open low vegetation is assumed to be adapted to its habitat by a relatively high NAR made possible by a high rate of photosynthesis concurrent with a high leaf N content. The growth ofC. acutiformis at a relatively nutrient-rich site and a more dense and higher vegetation is adapted to its habitat by a high LAR.     

Defense of termitaria by termitophilous ants

Summary Mounds of Amitermes laurensis are frequently faided by meat ants Iridomyrmex sanguineus. Of eight ant species which often cohabit with the termites, Camponotus sp. B and C were considerably dependent on the termintaria for their nest sites and effectively protected it from the attacks by meat ants. Many termite colonies cohabiting with those two ant species were vigorous, suggesting that this ant-termite relationship is mutualistic; thus, the ants were provided nest sites and probably even food and the termites were protected from destructive natural enemies.     

Leaf architectural studies in the brassicaceae

The leaf architecture has been studied in 19 genera and 35 species of the Brassicaceae. The major venation pattern is pinnate craspedodromous with the exception ofAlyssum maritimum, Iberis amara, I. umbellata andMalcolmia maritima where it is pinnate-festooned brochidodromous. The number of secondary veins and their angle of divergence vary from species to species and even within the same species. Marginal ultimate venation is mostly looped occasionally incomplete. The areole size and shape is variable. The veinlets may be simple or once or twice dichotomously divided. The simple veinlets may be curved or hooked. The tracheids are either uni-, bi-, tri- or multiseriate and extraordinarily variable in size and shape. Isolated vein endings, isolated free vein endings, isolated tracheids and extension cells are observed. Myrosin cells have been observed inEruca vesicaria ssp.sativa andCochlearia cochlearioides.     

The process of population increase and patterns of resource utilization of two spider mites,Oligonychus ununguis (Jacobi) andPanonychus citri (McGregor), under experimental conditions (Acari: Tetranychidae)

Summary Pattern of population growth and characteristics of habitat utilization and of migration by two species of spider mites were studied under experimental conditions. The population growth ofOligonychus ununguis (Jacobi) on a chestnut occurred only on a single mite-release leaf over a long period, and few individuals moved away. Most of the 2nd progeny generation females of this species emigrated from the mite-release leaf as well as the sapling by means of ballooning threads. During this growth period, population density on the mite-release leaf levelled off, whereas that on the sapling increased. In contrast, the foundress ofPanonychus citri (McGregor) on citrus actively moved over several neighbouring leaves, and until the 2nd progeny generation females emerged, individuals were distributed over all the sapling leaves by means of walking. Emigration from the sapling was not observed until the 2nd progeny females emerged, and after that the mites emigrated by means of ballooning threads. The population density ofP. citri on the sapling levelled off and was rather decreased on the mite-release leaf at the time of mite emigration. Comparing the changing pattern of the relative degree of aggregation (m ^*/m) measured in two different units between these two species, the pattern ofm ^*/m in 1 cm² on the mite release leaf inO. ununguis resembled that of the unit of leaves on the sapling inP. citri. This result as well as behavioural observations indicate that migration ofO. ununguis is the movement from leaf to leaf and that ofP. citri from sapling to sapling. It is, therefore, concluded that the boundary of the microhabitat is a single leaf forO. ununguis but sapling or foliage forP. citri. This work was presented in Annual Meeting of Jap. Soc. Appl. Ent. Zool., 1981 in Okayama.     

Daily patterns of abundance and temporal distributions of feeding, mating and oviposition of the dipteran leaf miner, Agromyza frontella

Observations of adult Agromyza frontella (Rondani) (Diptera: Agromyzidae) in alfalfa, Medicago sativa L. (cv. Saranac), fields in two regions of Quebec, Canada, demonstrated that males were most abundant on alfalfa plants early in the morning and in the late afternoon/early evening, which coincided with the occurrence of bimodal mating activity. Male abundance and incidence of mating were usually negatively correlated with air temperature, solar insolation and wind speed and positively correlated with relative humidity. The daily pattern of female abundance on alfalfa varied less than that of males. Females fed and oviposited throughout the day, and the frequency of these activities were usually positively correlated with air temperature and solar insolation and negatively correlated with relative humidity. Possible reasons for the sexual dimorphism in the daily activity patterns of this leaf miner, and their significance for individual fitness, are discussed.

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Résumé L'observation visuelle des adultes de la mineuse virgule de la luzerne, A. frontella, dans des champs de luzerne de deux regions differentes du Québec, ont démontré que les mâles étaient plus nombreux sur les plantes tôt le matin, vers la find de l'après — midi et tôt en soirée, ce qui a coincidé avec l'occurence bimodale de l'accouplement. L'abondance diurne des femelles variait moins que celle des mâles et les femelles se nourrissaient activement pendant toute la journée. La fréquence de l'alimentation et de la ponte chez les femelles (les mâles n'étant observé que très rarement en train de se nourrir) étaient corrélées positivement à la température ambiante de l'air de méme qu'à l'insolation mais étaient négativement corrélées à l'humidité relative. Contrairement aux femelles, l'abondance des mâles et l'incidence de l'accouplement étaient habituellement corrélées négativement à la température ambiante de l'air, à l'insolation et à la vitesse du vent alors qu'elles étaient positivement corrélées à l'humidité relative. Plusieurs hypothèses pouvant expliquer le dimorphisme sexuelle des activitées diurnes de cette mineuse ainsi que leurs implications quant à la fitness, des individus, sont discutés.

     

Soil and plant water relations in a crested wheatgrass pasture: response to spring grazing by cattle

Summary Few field studies have attempted to relate effects of actual livestock grazing on soil and plant water status. The present study was initiated to determine the effects of periodic defoliations by cattle during spring on soil moisture and plant water status in a crested wheatgrass (Agropyron cristatum (L.) Gaertn. and A. desertorum (Fisch. ex Link) Schult.) pasture in central Utah. Soil moisture in the top 130 cm of the soil profile was depleted more rapidly in ungrazed plots than in grazed plots during spring and early summer. Soil moisture depletion was more rapid in grazed plots in one paddock after 1 July due to differential regrowth, but there was no difference in soil water depletion between plots in another paddock during the same period. This difference in soil water depletion between paddocks was related to a difference in date of grazing. Although more water had been extracted from the 60 cm to 130 cm depths in ungrazed plots by late September, cumulative soil moisture depletion over the entire 193 cm profile was similar in grazed and ungrazed plots. Prior to 1 July, grazing had no effect on predawn leaf water potentials as estimated by a pressure chamber technique; however, after 1 July, predawn leaf water potentials were lower for ungrazed plants. Midday leaf water potentials were lower for grazed plants before 1 July, but did not differ between grazed and ungrazed plants after 1 July. A 4- to 8-day difference in date of defoliation did not affect either predawn or midday leaf water potentials. The observed differences in water use patterns during spring and early-summer may be important in influencing growth and competitive interactions in crested wheatgrass communities that are subject to grazing by domestic livestock.     

Effects of fungal endophytes on the seed and seedling biology of Lolium perenne and Festuca arundinacea

Summary Many grasses are infected by endophytic fungi that grow intercellularly in leaves, stems, and flowers and are transmitted maternally by hyphal growth into ovules and seeds. The seed biology and seedling growth of endophyte-infected and uninfected perennial ryegrass (Lolium perenne) and tall fescue (Festuca arundinacea) were investigated under controlled environmental conditions. The percentage of filled seeds produced by infected tall fescue was over twice of uninfected tall fescue; infected and uninfected perennial reegrass had similar percentages. Weights of seeds from infected and uninfected plants were similar in both species. Seeds from infected plants of both species exhibited a higher rate of germination than seeds from uninfected plants. Shoot growth in the greenhouse was compared by making three sequential harvests of above-ground plant parts from infected and uninfected plants of both species. Infected perennial ryegrass plants produced significantly more biomass and tillers than uninfected plants after 6 and 10 weeks of growth and significantly more biomass after 14 weeks of growth. Infected tall fescue plants produced significantly more biomass and tillers than uninfected plants after 10 and 14 weeks of growth. The physiological mechanism of enhancement of growth is not known. The results of this study suggest that infected plants may have a selective advantage in populations with uninfected members.     

Changes at panicle emergence in the water relations of a wetland and a dryland Japonica rice cultivar under wetland conditions

The diurnal and seasonal changes in plant water relations of two Japonica rice ( Oryza sativa L.) cultivars, Nipponbare and Tachiminori, were studied under flooded conditions at Kyoto University. The dryland cv. Tachiminori maintained higher predawn and midday leaf osmotic potentials relative to the wetland cv. Nipponbare during the vegetative stage, but the ranking was reversed after flowering. The relationship between leaf water potential and leaf osmotic potential showed that prior to panicle emergence Nipponbare was able to adjust osmotically to maintain turgor, whereas after heading there was little turgor maintenance. Tachiminori showed little difference in osmotic adjustment before and after panicle emergence. Fertilizer treatment during panicle development also helped to maintain the degree of osmotic adjustment in both cultivars.     

Pinus radiata D. Don in Chile. Fertilization trials with copper

Summary YoungPinus radiata D. Don were fertilized with copper oxychloride and copper sulfate on a random block basis with four replicates. Roots, needles, stems and shoot apices were analyzed separately for Cu, Fe, Mn and Zn contents at different times from fertilization. The results showed a rapid plant copper absorption, no effects being found on the Fe, Mn and Zn content. The dynamic internal distribution of copper among different plant parts is shown. The treatments applied did not cause any phenotypical alteration nor phytotoxicity in the plants, and no significant effect of the fertilizer chemicals on each other.     

Effects of salinity and varying boron concentrations on boron uptake and growth of wheat

Summary Two sandculture experiments were conducted with wheat (Triticum aestivum) to determine the effects of (1) osmotic potential (Ψ_π) and (2) fluctuating boron (B) concentrations on B availability (toxicity), shoot growth and leaf concentrations of B of wheat. The first experiment consisted of growing wheat to the spike emergence stage in sandcultures irrigated with a complete nutrient solution containing 1.0, 7.5, and 15.0 mg Bl⁻¹ and having Ψ_π values of −0.02, −0.07, −0.12, and −0.17 MPa produced by CaCl₂−NaCl additions. Statistically, shoot weight was independently influenced by the B and Ψ_π treatments but not by their interaction. Only the B treatment had a significant effect on leaf boron concentrations; the B x Ψ_π interaction was nonsignificant with respect to leaf B concentrations. The second experiment was designed to determine if growth and B uptake of wheat responds to the time integrated mean (TIM) concentration of B. This experiment consisted of four fixed-B concentrations and four fluctuating-B concentrations designed to produce two TIM concentrations (3.9 and 7.4 mg Bl⁻¹) approached low to high and vice versa. With respect to shoot weight, there was no statistical difference among treatments having the same TIM concentration during the 10 week experiment. However, shoot B concentrations differed greatly; they were higher when the B concentration was progressively increased over the 10 week period. Leaf B concentrations (Y leaf at flowering), while not as high as the shoot B concentrations, were also higher under the treatment of increasing B concentration, indicating B uptake rates are higher for mature plants than for seedlings.