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Shoot Length (shoot + length)

Distribution by Scientific Domains

Life Sciences	68%

Distribution within Life Sciences

Conservation Science	17%

Selected Abstracts

Varietal Differences in Development of Maize (Zea mays L.) Seedlings on Compacted Soils

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2001
L. O. Soyelu
Differences among open-pollinated tropical maize (Zea mays L.) varieties in seedling development and establishment on compacted soils were studied. Soil dry density was used as an index of compaction. Three soil compaction levels and 12 traits associated with development and establishment of maize seedlings were investigated. A control (without compaction) was also included. Varietal differences were observed for most traits measured. Genetic differences for seedling development on compacted soil were detected. Varietal differences contributed about three times the contribution of compaction to total variability in the traits. Better seedling development and performance were obtained in moderately compacted soil than in the control. Shoot length, shoot dry weight and per cent dry matter in roots were good indicators of the tolerance of maize seedlings to compaction. A physiological strategy for maize seedling establishment on compacted soil was proposed. The implications of the results for seed testing were also highlighted. It was concluded that consideration should be given to the genotype of maize destined for use in ecologies prone to high soil densities. All varieties of maize grown in an agroecological zone could be screened to identify genotypes tolerant of higher soil densities. The seeds could then be multiplied and distributed to farmers. Sortenunterschiede in der Entwicklung von Mais (Zea mays L.)-Sämlingen in verdichteten Böden Sortenunterschiede der Sämlingsentwicklung und des Aufwuchses wurden in verdichteten Böden bei fremdbestäubenden tropischen Mais (Zea mays L.)-Sorten untersucht. Die Bodentrockendichte wurde als Index für die Verdichtung verwendet. Drei Verdichtungsstärken und zwölf Behandlungen im Zusammenhang mit der Entwicklung und dem Anwuchs von Maissämlingen wurden untersucht. Eine Kontrolle (ohne Bodenverdichtung) wurde berücksichtigt. Sortenunterschiede wurden für die meisten Eigenschaften gemessen. Genetische Differenzen der Sämlingsentwicklung in verdichteten Böden konnten beobachtet werden. Sortendifferenzen trugen etwa dreifach im Vergleich zur Bodenverdichtung im Hinblick auf die Gesamtvariabilität der Eigenschaften bei. Bessere Sämlingentwicklung und Sämlingsleistung wurden an moderat verdichteten Böden im Vergleich zur Kontrolle beobachtet. Die Sprosslänge, das Sprosstrockengewicht und die Trockenmasse prozent in Wurzeln gaben gute Hinweise hinsichtlich der Toleranz der Maissämlinge gegenüber Bodenverdichtung. Eine physiologische Strategie für die Maissämlingsentwicklung in verdichteten Böden wird vorgeschlagen. Die Bedeutung der Ergebnisse für Samentestzwecke wurde betont. Es wird angenommen, dass Genotypen für den Anbau in ökologischen Bedingungen, die starke Bodenverdichtungen aufweisen, berücksichtigt werden sollten. Da viele Maissorten in agroökologischen Gebieten angebaut werden, sollten diese getestet werden, um Genotypen mit Toleranz gegenüber stärkerer Bodenverdichtung zu identifizieren. Diese Samen könnten dann vermehrt und an Landwirt abgegeben werden. [source]

The effect of soil compaction on germination and early growth of Eucalyptus albens and an exotic annual grass

AUSTRAL ECOLOGY, Issue 6 2009
ALISON K. SKINNER
Abstract Most agricultural land has been compacted to some degree by heavy machinery or livestock trampling. This legacy is expected to influence the success of tree seedling recruits in farmland areas where natural regeneration is being encouraged. We investigated the impact of soil compaction on seedlings of a woodland eucalypt (Eucalyptus albens) and an annual grass competitor (Vulpia myuros) in a laboratory experiment. Replicate soil cores were created at five bulk density levels; 1.0, 1.1, 1.2, 1.3 or 1.4 Mg m,3 with a soil water content of 20%. The depth of root penetration declined linearly with increasing bulk density, resulting in a decrease in root depth of around 75% in the most compacted soil compared with the least compacted soil for both species. Shoot length and primary root length did not vary between soil bulk density levels for either species, but seedlings responded to increasing levels of compaction with oblique (non-vertical) root growth. Results suggest that young seedlings of both E. albens and V. myuros will be more susceptible to surface drying in compacted than uncompacted soils and therefore face a greater risk of desiccation during the critical months following germination. Any competitive advantage that V. myuros may have over E. albens is not evident in differential response to soil compaction. [source]

Patterns of interspecific associations of stem gallers on willows

DIVERSITY AND DISTRIBUTIONS, Issue 6 2003
Jens-Peter Kopelke
Abstract., The pattern of interspecific associations of three stem-galling sawfly species (Euura atra, E. elaeagnos, E. purpureae) and three stem-galling gallmidge species (Rabdophaga sp. 3,5) was investigated on five willow taxa (Salix alba, S. fragilis, S. × rubens, S. elaeagnos, S. purpurea) at five natural sites in Central Europe. The willow species harboured specific species associations of two stem gallers, each pair consisting of one Euura and one Rabdophaga species. The stem gallers were patchily distributed and their densities varied significantly among willow host plant species, host plant individuals, and host plant sexes. Four of the six species showed a significant increase in galling rate with shoot length. The other two species were the sawfly and cecidomyiid pair that induce galls on S. purpurea. The preference of stem gallers to longer shoots was generally not related to higher larval performance in terms of survival. Only one species, Rabdophaga sp. 5, was found to be more abundant on male plants. The correlation of densities of the species pairs of stem gallers was independent of willow sexes. Species pairs of stem gallers co-occurring on the same willow species tended to attack different shoots within the same host plant individual. When species pairs co-occurred on shoots they were usually found in similar densities as when occurring alone on shoots. The stem-galling sawflies usually formed galls at the basal part of a shoot, whereas the gallmidge R. sp. 5 (R. sp. 3 and R. sp. 4 showed no clear tendency) preferred the middle or distal part of a shoot. This is interpreted with differences of their phenology and oviposition period. [source]

Post-gall induction performance of Adelges Abietis (L.) (Homoptera: Adelgidae) is influenced by clone, shoot length, and density of colonising gallicolae

ECOLOGICAL ENTOMOLOGY, Issue 1 2010
LEAH FLAHERTY
1. We evaluated the effect of clone (one susceptible and one resistant clone), shoot length, crown level, and gallicola density on post-gall induction performance of Adelges abietis. Galls that had been successfully induced by one fundatrix on a range of shoot sizes were selected, and the number of gallicolae that could colonise the gall was manipulated. 2. Post-induction gall development success was inversely related to shoot length and was higher on the susceptible clone than on the resistant clone. As gallicola density did not influence the proportion of galls that successfully completed development, reduced post-induction gall development on large shoots was not likely to be result of an insufficient stimulus from gallicolae. 3. Clone was the only factor that significantly influenced gall volume and galls were larger on the susceptible clone than on the resistant clone. As gall volume did not increase when more gallicolae attempted to colonise a gall, competition within a gall increased. Gallicola survival was inversely related to the number of colonising gallicolae. Our results suggest that gall size may be limiting at natural densities. 4. Previous studies report positive relationships between gall induction success and fundatrix density, and between gall size and fundatrix density. As each fundatrix produces one egg mass of gallicolae, this study suggests that there may be a trade-off between the successful induction of a large gall and subsequent survival of gallicolae. 5. In the present study, clone influenced all measures of post-gall induction performance. Performance was always higher on the susceptible than on the resistant clone. [source]

Host plant variation in plant-mediated indirect effects: moth boring-induced susceptibility of willows to a specialist leaf beetle

ECOLOGICAL ENTOMOLOGY, Issue 2 2008
SHUNSUKE UTSUMI
Abstract 1.,We examined the plant-mediated indirect effects of the stem-boring moth Endoclita excrescens (Lepidoptera: Hepialidae) on the leaf beetle Plagiodera versicolora (Coleoptera: Chrysomelidae) in three willow species, Salix gilgiana, S. eriocarpa, and S. serissaefolia. 2.,When the stem-boring moth larvae damaged stems in the previous year, willows were stimulated to produce vigorously growing lateral shoots on these stems. These new lateral shoots were significantly longer and the upper leaves had significantly higher nitrogen and water content than current-year shoots on unbored stems, although the carbon content and leaf dry mass were not different between lateral and current-year shoots. 3.,In the field, leaf beetle larvae and adults had significantly greater densities on lateral shoots of bored stems than on current-year shoots of unbored stems. A laboratory experiment showed that female beetles had significantly greater mass and fecundity when fed on leaves of newly-emerged lateral shoots. Thus, the stem-boring moth had a positive effect on the temporally and spatially separated leaf beetle by increasing resource availability by inducing compensatory regrowth. 4.,The strength of the indirect effects on the density and performance of the leaf beetle differed among willow species, because there was interspecific variation in host quality and herbivore-induced changes in plant traits. In particular, we suggest that the differences in magnitude of the changes among willow species in shoot length and leaf nitrogen content greatly affected the strength of the plant-regrowth mediated indirect effect, coupled with host-plant preference of the leaf beetle. [source]

Interactions between cottonwood and beavers positively affect sawfly abundance

ECOLOGICAL ENTOMOLOGY, Issue 4 2006
JOSEPH K. BAILEY
Abstract 1.,Cottonwood (Populus spp.) are the dominant tree type in riparian forests of the western U.S.A. In these riparian forests, the beaver (Castor canadensis) is a major ecosystem engineer that commonly browses cottonwood, resulting in distinct changes to plant architecture. Here the hypothesis that beaver herbivory indirectly affects the distribution of a keystone leaf-galling sawfly through architectural changes in cottonwood was examined. 2.,It was found that: (a) beaver herbivory of cottonwood results in an increase in average shoot length over unbrowsed cottonwood; (b) sawfly galls were up to 7,14 times more abundant on browsed cottonwood than unbrowsed cottonwood; and (c) sawfly gall abundance was correlated positively with changes in shoot length after beaver herbivory. Together these data show that the individual and combined effects of cottonwood and beaver herbivory increase shoot length, positively affecting sawfly abundance. 3.,Because herbivores are a ubiquitous component of most ecosystems, we argue that the indirect effects of herbivory on plant quality, and subsequently other herbivores, may be as important as environmental variation. [source]

Long-term ozone effects on vegetation, microbial community and methane dynamics of boreal peatland microcosms in open-field conditions

GLOBAL CHANGE BIOLOGY, Issue 8 2008
SAMI K. MÖRSKY
Abstract To study the effects of elevated ozone concentration on methane dynamics and a sedge species, Eriophorum vaginatum, we exposed peatland microcosms, isolated by coring from an oligotrophic pine fen, to double ambient ozone concentration in an open-air ozone exposure field for four growing seasons. The field consists of eight circular plots of which four were fumigated with elevated ozone concentration and four were ambient controls. At the latter part of the first growing season (week 33, 2003), the methane emission was 159±14 mg CH4 m,2 day,1 (mean±SE) in the ozone treatment and 214±8 mg CH4 m,2 day,1 under the ambient control. However, towards the end of the experiment the ozone treatment slightly, but consistently, enhanced the methane emission. At the end of the third growing season (2005), microbial biomass (estimated by phospholipid fatty acid biomarkers) was higher in peat exposed to ozone (1975±108 nmol g,1 dw) than in peat of the control microcosms (1589±115 nmol g,1 dw). The concentrations of organic acids in peat pore water showed a similar trend. Elevated ozone did not affect the shoot length or the structure of the sedge E. vaginatum leaves but it slightly increased the total number of sedge leaves towards the end of the experiment. Our results indicate that elevated ozone concentration enhances the general growth conditions of microbes in peat by increasing their substrate availability. However, the methane production did not reflect the increase in the concentration of organic acids, probably because hydrogenotrophic methane production dominated in the peat studied. Although, we used isolated peatland microcosms with limited size as study material, we did not find experimental factors that could have hampered the basic conclusions on the effects of ozone. [source]

Assessment of Growth, Physiological and Biochemical Parameters and Activities of Antioxidative Enzymes in Salinity Tolerant and Sensitive Basmati Rice Varieties

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 6 2007
M. P. Singh
Abstract This investigation was undertaken to compare the level of salinity tolerance of the newly bred CSR-30 basmati rice variety with that of the salinity sensitive HBC-19 and Pokkali rice varieties. Twenty-one-day-old hydroponically raised seedlings at 6 and 12 dS m,1 were investigated for growth, photosynthetic rate, chlorophyll content, ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) activity, relative water content (RWC), membrane stability index (MSI), lipid peroxidation, Na/K ratio and activities and gene expression of various isoforms of antioxidative enzymes. Salinity stress led to reduction in shoot length, leaf area, dry weight, RWC, MSI, rate of photosynthesis, chlorophyll content and Rubisco activity in all the three rice varieties. The levels of reduction in these parameters were maximal in HBC-19 followed by those in CSR-30 and Pokkali respectively. Cumulative superoxide dismutase (SOD) activity increased in Pokkali and CSR-30 in consonance with increase in salinity stress while it decreased in HBC-19. The Mn-SOD activity however, was enhanced in all three varieties in the presence of salinity stress while the activities of Fe-SOD, Cu/Zn-SOD and ascorbate peroxidase were decreased in HBC-19 when compared with CSR-30 and Pokkali. The activity of catalase (CAT) was higher in HBC-19 when compared with its activity in CSR-30 and Pokkali. The levels of gene expressions of the three isoforms of SOD ascertained by reverse transcriptase polymerase chain reaction were not necessarily indicative of the activities of the corresponding enzymes. Thus, despite the maximal enhancement in gene expression of Fe-SOD in HBC-19 in response to salinity stress, the activity of this enzyme in HBC-19 remained low. Similarly, despite a marginal increase in gene expression of Cu-Zn SOD in the three varieties, its activity was significantly higher in Pokkali and CSR-30 when compared with that in HBC-19. A significant enhancement in the activity of CAT at 12 dS m,1 in HBC-19 when compared with CSR-30 and Pokkali might confer a degree of tolerance to H2O2 stress in this variety in the presence of higher levels of NaCl at the seedling stage. [source]

Indices of Drought Tolerance in Wheat Genotypes at Early Stages of Plant Growth

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 1 2004
S. S. Dhanda
Abstract Thirty diverse genotypes of bread wheat were evaluated for seed vigour index, germination percentage, root length, shoot length, root-to-shoot length ratio, coleoptile length and osmotic membrane stability under laboratory conditions. Considerable variation was observed for all the characters. Discrimination among the genotypes on the basis of mean values was better under normal than under moisture stress conditions, indicating suppression of variability under moisture stress conditions. Comparison of mean performance under normal and osmotic stress conditions indicated that the seed vigour index was the most sensitive trait, followed by shoot length, germination percentage and root length. The root-to-shoot length ratio, however, increased under osmotic stress. The magnitude of genetic components of variance and heritability were, in general, lower under osmotic stress than under normal conditions. All the characters except germination percentage, shoot length and coleoptile length showed considerable genetic variability. Heritability in the broad sense was also moderate to high for all the characters under both environments. Due to high heritability and genetic advance great benefit from selection can be expected for the osmotic membrane stability of leaf segments and root-to-shoot length ratio. Moderate progress can be expected from root length and seed vigour index. Correlation studies indicated that the osmotic membrane stability of the leaf segment was the most important trait, followed by root-to-shoot ratio and root length on the basis of their relationships with other traits. [source]

Allelopathic Effects of Parthenium hysterophorus Extracts on Seed Germination and Seedling Growth of Eragrostis tef

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 5 2002
T. Tefera
The present study was conducted to investigate the allelopathic effects of Parthenium hysterophorus weed on seed germination and seedling growth of tef. Flower, stem, root and leaf aqueous extracts of Parthenium at 0, 1, 5, and 10 % concentrations were applied to determine their effect on tef seed germination and seedling growth under laboratory conditions. Increasing concentrations of aqueous extracts of Parthenium from leaf and flower inhibited seed germination and complete failure of seed germination was recorded when the extract concentration from the leaf part was 10 %. In contrast, aqueous extracts from stem and root had no effect on tef seed germination. Roots appeared more sensitive to allelopathic effect than shoots. Extracts from flower, root and stem had a stimulatory effect on shoot length at all concentration levels, as against an inhibitory effect of leaf extracts. Root extracts at low concentration (1 %) greatly promoted root length but aqueous extracts from leaf and flower inhibited root length. [source]

Response of Faidherbia albida (Del.) A. Chev., Acacia nigrescens Oliver. and Acacia nilotica (L.) Willd ex Del. seedlings to simulated cotyledon and shoot herbivory in a semi-arid savanna in Zimbabwe

AFRICAN JOURNAL OF ECOLOGY, Issue 2 2010
Sijabulile Dube
Abstract Woody plant seedling establishment is constrained by herbivory in many semi-arid savannas. We clipped shoots and cotyledons of three woody species 5-day (=,early') or 28-day (= ,late') post-emergence to simulate herbivory. Seedlings had shoot apex, one or two cotyledon(s) removed, or were retained intact. Survival rates were ,80%, ,40% and ,20% for Acacia nilotica, Acacia nigrescens and Faidherbia albida respectively. F. albida mobilized stored cotyledon reserves faster and consequently shed the cotyledons earlier than the two Acacia species. Cotyledons were shed off as late as 70 days post-emergence with 5-day shedding earlier than 28-day and cotyledon life-span decreasing with intensity of defoliation. Shoot apex removal 28-day resulted in higher compensatory growth than 5-day in all three species. Cotyledon removal had no effect on shoot length, while shoot apex removal reduced shoot length. In F. albida root growth was stimulated by shoot apex removal. We conclude that potential tolerance to herbivory in terms of seedling survival was of the order A. nilotica > A. nigrescens > F. albida, timing of shoot apex and cotyledon removal influenced seedling growth in terms of biomass and that shoot apex removal stimulated compensatory growth which is critical to seedling survival. Résumé L'établissement de jeunes plants ligneux est contrarié par l'herbivorie dans de nombreuses savanes semi arides. Nous avons coupé les pousses et les cotylédons de trois espèces ligneuses à 5-j (= tôt) ou à 28 j (= tard) après leur émergence pour simuler l'herbivorie. On coupait l'apex de la tige et un ou deux cotylédons, ou on les laissait intacts. Le taux de survie était , 80%, , 40% et , 20% pour Acacia nilotica, Acacia nigrescensetFaidherbia albida respectivement. F. albida mobilisait plus rapidement les réserves stockées dans les cotylédons et par conséquent perdait les cotylédons plus tôt que les deux espèces d'acacia. Les cotylédons étaient perdus jusqu'à 70 jours après leur apparition, les 5-j les perdant plus tôt que les 28-j, et la durée de vie des cotylédons diminuait avec l'intensité de la défoliation. L'enlèvement des cotylédons n'avait pas d'effet sur la longueur de la pousse, tandis que celui de l'apex la réduisait. Chez F. albida, la croissance des racines était stimulée par l'enlèvement de l'apex. Nous concluons que la tolérance potentielle à l'herbivorie, en termes de survie des jeunes plants, suit cet ordre-ci : A. nilotica > A. nigrescens > F. albida; que le moment de l'enlèvement du bourgeon apical et des cotylédons influence la croissance des jeunes plants en termes de biomasse; et que l'enlèvement du bourgeon apical stimule une croissance compensatoire qui est critique pour la survie du jeune plant. [source]

Strong evidence for a fire blight resistance gene of Malus robusta located on linkage group 3

PLANT BREEDING, Issue 5 2007
A. Peil
Abstract Fire blight (FB), caused by the Gram-negative bacterium Erwinia amylovora is a dangerous disease on pome fruit, including apple. The FB-susceptible cultivar ,Idared' was crossed with the resistant wild species clone Malus × robusta 5. A segregating population of 146 progeny has been tested by artificial shoot inoculation for susceptibility to FB. Progeny were infected from 0% to 100% of the shoot length. To identify chromosomal regions or loci responsible for resistance to FB of Malus × robusta 5, a set of microsatellite markers (simple sequence repeat, SSRs) was chosen covering all linkage groups of apple. Up to eight different microsatellites were bulked to one mutliplex PCR using four different labels and a fifth label for a size standard. Fifty-nine microsatellite markers out of 72 SSRs were polymorphic. Fifty-four of 66 loci detected could be mapped and were useful for the detection of related resistant loci. Alleles of microsatellites Hi03d06, CH03g07 and CH03e03 originating from the resistant donor M. robusta were associated with resistance to Erwinia amylovora. Up to eighty percent of the phenotypic variation could be explained by the interval spanned by SSRs CH03g07 and CH03e03, indicating the presence of a major resistance gene. All three microsatellites are located on the distal part of linkage group 3, spanning 15 cM. The SSR marker CH03e03 can be regarded as diagnostic marker for FB resistance. Only seven progeny expressing allele b (184 bp) of CH03e03 showed blighted shoot lengths of more than 30% and only nine progeny lacking allele b showed blighted shoot lengths of <30%. By setting a threshold of 30% shoot necrosis for resistance to FB, the 146 individuals segregate into 71 susceptible and 75 resistant plants, and resistance to FB maps 9 cM away from marker CH03e03. [source]

Influence of imidacloprid seed treatments on rice germination and early seedling growth

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2008
Mark M Stevens
Abstract BACKGROUND: Seed treatments with the chloronicotinyl insecticide imidacloprid (Gaucho® 600 FS) were evaluated to determine whether differences in concentration and exposure regime influence the germination and early growth of rice. RESULTS: Continuous exposure to imidacloprid (4 days at 2000 mg AI L,1) significantly (P < 0.001) reduced normal germination by an average of 18% across the 15 cultivars examined. Nine days after sowing, plants showed no adverse effects from continuous imidacloprid treatment during germination, with shoot lengths and root system dry weights equalling, or occasionally exceeding (P < 0.05), those of untreated plants. Short-term imidacloprid exposure (2 h at 2000 mg L,1) at initial seed wetting did not affect germination (P > 0.05), and short-term (1 h) exposure of 48 h pregerminated seed to imidacloprid (2000 mg L,1) similarly had no significant effect on early subsequent growth. Plants arising from 48 h pregerminated seed exposed to imidacloprid (1 h) at concentrations up to 4000 mg L,1 immediately before sowing were not significantly different from control plants at either 9 or 25 days post-sowing. CONCLUSION: Results show that imidacloprid will have no adverse effects on plant growth if applied to pregerminated rice shortly before sowing. Continuous exposure of seed during germination had more pronounced effects, and the initial response of different cultivars was highly variable. Cultivars with high levels of sensitivity (such as IR72) require further testing before continuous exposure to imidacloprid during germination can be recommended. Copyright © 2007 Society of Chemical Industry [source]