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Internode Length (internode + length)
Selected AbstractsLocal forest environment largely affects below-ground growth, clonal diversity and fine-scale spatial genetic structure in the temperate deciduous forest herb Paris quadrifoliaMOLECULAR ECOLOGY, Issue 14 2005HANS JACQUEMYN Abstract Paris quadrifolia (herb Paris) is a long-lived, clonal woodland herb that shows strong differences in local population size and shoot density along an environmental gradient of soil and light conditions. This environmentally based structuring may be mediated by differences in clonal growth and seedling recruitment through sexual reproduction. To study the interrelationship between environmental conditions and spatial patterns of clonal growth, the spatial genetic structure of four P. quadrifolia populations growing in strongly contrasting sites was determined. In the first place, plant excavations were performed in order to (i) determine differences in below-ground growth of genets, (ii) investigate connectedness of ramets and (iii) determine total genet size. Although no differences in internode length were found among sites, clones in moist sites were much smaller (genets usually consisted of 1,3 interconnected shoots, most of them flowering) than genets in dry sites, which consisted of up to 15 interconnected shoots, the majority of which were vegetative. Further, amplified fragment length polymorphism (AFLP) markers were used. Clonal diversity was higher in populations located in moist and productive ash,poplar forests compared to those found in drier and less productive mixed forest sites (G/N: 0.27 and 0.14 and Simpson's D: 0.84 and 0.75, respectively). Patterns of spatial population genetic structure under dry conditions revealed several large clones dominating the entire population, whereas in moist sites many small genets were observed. Nevertheless, strong spatial genetic structure of the genet population was observed. Our results clearly demonstrate that patterns of clonal diversity and growth form of P. quadrifolia differ among environments. Limited seedling recruitment and large clone sizes due to higher connectedness of ramets explain the low clonal diversity in dry sites. In moist sites, higher levels of clonal diversity and small clone sizes indicate repeated seedling recruitment, whereas strong spatial genetic structure suggests limited seed dispersal within populations. [source] Red to far-red ratio correction in plant growth chambers , growth responses and influence of thermal load on garden peaPHYSIOLOGIA PLANTARUM, Issue 2 2007Ian G. Cummings Plant growth chambers are commonly used to minimize environmental variation but the light sources used vary considerably from natural light and from each other. Incandescent globes are often used to add more far-red light, with the aim of producing a more natural red to far-red ratio (R:FR), but also add to thermal load. High-intensity discharge lamps are often used to produce higher irradiances, more akin to natural light, but the thermal implications are rarely considered because air temperature is controlled. This paper examines the spectral properties and thermal implications of growth chamber light sources and takes a whole-plant physiology approach, by examining growth responses of a photoperiodic pea line (Pisum sativum L. cv. Torsdag) in the same growth chamber type under different light sources , in essence using plants to study the controlled environments rather than vice-versa. High R:FR delayed flowering and inhibited internode extension in pea. However, the addition of far-red-rich incandescent globes in the proportions provided in the growth chambers (400,500 W) did little to reduce R:FR, did not induce earlier flowering and actually further inhibited internode length. Leaflet size and yield were significantly reduced. While air temperature was maintained at 20°C in all experiments, radiant temperature was significantly higher under high irradiance and/or with incandescent added, and soil temperatures were elevated. Growth responses under these lights were similar to the effect caused by elevating the air temperature. An alternative method of controlling R:FR, without thermal load implications, using light-emitting diodes is described. [source] In vitro quantification of barley reaction to leaf stripePLANT BREEDING, Issue 5 2003M. I. E. Arabi Abstract An in vitro technique was used to quantify the infection level of leaf stripe in barley caused by Pyrenophora graminea. This pathogen penetrates rapidly through subcrown internodes during seed germination of susceptible cultivars. Quantification was based on the percentage of the pieces of subcrown internodes that produced fungal hyphae cultured on potato dextrose agar media. The disease severity was evaluated among five cultivars with different infection levels and numerical values for each cultivar were obtained. A significant correlation coefficient (r = 0.91, P < 0.02) was found among the in vitro and field assessments. In addition, the results were highly correlated (r = 0.94, P < 0.01) among the different in vitro experiments, indicating that this testing procedure is reliable. The method presented facilitates a rapid preselection under uniform conditions which is of importance from a breeder's point of view. Significant differences (P < 0.001) were found for the length of subcrown internodes between inoculated and non-inoculated plants with leaf stripe. Isolate SY3 was the most effective in reducing the subcrown internode length for all genotypes. [source] Counteractive biomass allocation responses to drought and damage in the perennial herb Convolvulus demissusAUSTRAL ECOLOGY, Issue 5 2010IVÁN M. QUEZADA Abstract Herbivory and water shortage are key ecological factors affecting plant performance. While plant compensatory responses to herbivory include reallocation of biomass from below-ground to above-ground structures, plant responses to reduced soil moisture involve increased biomass allocation to roots and a reduction in the number and size of leaves. In a greenhouse study we evaluated the effects of experimental drought and leaf damage on biomass allocation in Convolvulus demissus (Convolvulaceae), a perennial herb distributed in central Chile, where it experiences summer drought typical of Mediterranean ecosystems and defoliation by leaf beetles and livestock. The number of leaves and internode length were unaffected by the experimental treatments. The rest of plant traits showed interaction of effects. We detected that drought counteracted some plant responses to damage. Thus, only in the control watering environment was it observed that damaged plants produced more stems, even after correcting for main stem length (index of architecture). In the cases of shoot : root ratio, relative shoot biomass and relative root biomass we found that the damage treatment counteracted plant responses to drought. Thus, while undamaged plants under water shortage showed a significant increase in root relative biomass and a significant reduction in both shoot : root ratio and relative shoot biomass, none of these responses to drought was observed in damaged plants. Total plant biomass increased in response to simulated herbivory, apparently due to greater shoot size, and in response to drought, presumably due to greater root size. However, damaged plants under experimental drought had the same total biomass as control plants. Overall, our results showed counteractive biomass allocation responses to drought and damage in C. demissus. Further research must address the fitness consequences under field conditions of the patterns found. This would be of particular importance because both current and expected climatic trends for central Chile indicate increased aridity. [source] Ecological play in the coevolutionary theatre: genetic and environmental determinants of attack by a specialist weevil on milkweedJOURNAL OF ECOLOGY, Issue 6 2003Anurag A. Agrawal Summary 1We studied the genetic and environmental determinants of attack by the specialist stem-attacking weevil, Rhyssomatus lineaticollis on Asclepias syriaca. 2In natural populations, the extent of stem damage and oviposition were positively correlated with stem width, but not stem height. We hypothesized that both genotypic and environmental factors influencing stem morphology would affect attack by weevils. 3In a common garden study with 21 full-sib families of milkweed, both phenotypic and genetic correlations indicated that weevils impose more damage and lay more eggs on thicker stemmed plants. 4Of three other putative resistance traits, only latex production showed a negative genetic correlation with weevil attack. 5When neighbouring grasses were clipped to reduce light competition, focal milkweed plants received up to 2.6 times the photosynthetically active radiation and 1.6 times the red to far red ratio of light compared with plants with intact grass neighbours. Focal milkweed plants were therefore released from the classic neighbour avoidance response and had 20% shorter internode lengths, were 30% shorter, and had 90% thicker stems compared with controls. 6Clipping of grass neighbours resulted in nearly 2.7 times the damage and oviposition by stem weevils, thus supporting the hypothesis of an environmental or trait-mediated indirect influence on resistance. 7Although attack of plants by weevils strongly increases the probability of stem mortality, thicker stems experience lower mortality, thus counteracting the selective impact of weevil-induced plant mortality. 8The determinants of attack on milkweeds include both genetic variation for stem thickness and an indirect environmental influence of plant neighbours. If milkweeds and weevils are coevolving, the interaction is diffuse because the ecological neighbourhood is likely to modify the patterns of reciprocal natural selection. [source] Age-related myelin dynamics revealed by increased oligodendrogenesis and short internodesAGING CELL, Issue 2 2009Jurate Lasiene Summary Aging is associated with many functional and morphological central nervous system changes. It is important to distinguish between changes created by normal aging and those caused by disease. In the present study we characterized myelin changes within the murine rubrospinal tract and found that internode lengths significantly decrease as a function of age which suggests active remyelination. We also analyzed the proliferation, distribution and phenotypic fate of dividing cells with Bromodeoxyuridine (5-bromo-2-deoxyuridine, BrdU). The data reveal a decrease in glial cell proliferation from 1 to 6, 14 and 21 months of age in gray matter 4 weeks post-BrdU injections. However, we found an increase in gliogenesis at 21st month in white matter of the spinal cord. Half of newly generated cells expressed NG2. Most cells were positive for the early oligodendrocyte marker Olig2 and a few also expressed CC1. Very few cells ever became positive for the astrocytic markers S100, or GFAP. These data demonstrate ongoing oligodendrogenesis and myelinogenesis as a function of age in the spinal cord. [source] | ||||||||||