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Growing Conditions (growing + condition)

Distribution by Scientific Domains

Life Sciences	75%
Earth and Environmental Science	10%
3 Other Domains	15%

Distribution within Life Sciences

Plant Science	33%
Evolution	13%

Selected Abstracts

Sensitivity of Crops to Increased Ultraviolet Radiation in Northern Growing Conditions

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 1 2002
K. Hakala
Crops growing at high latitudes are adapted to low intensities of solar ultraviolet B radiation (UV-B). As a result of destruction of stratospheric ozone layer especially at the Polar Regions of the globe, the intensity of UV-B is projected to increase at high latitudes. In order to find out the consequences of increased UV-B on crops, the sensitivity of different varieties of barley, wheat, oats, clover, timothy, meadow fescue, tall fescue and potato was tested in Jokioinen, Finland. The experiment was conducted in the field, under natural light, with a continuous 30 % increase in UV-B. Both increased UV-B and the control with slightly increased UV-A radiation affected the number of lateral shoots in cereals, and the specific leaf area and the content of phenolic substances in grasses. The effects varied according to plant variety and time of growing season. However, no visible damage, nor changes in biomass and yield production were found in any of the crops. Long-term effects on, e.g. genetic stability and germination of crop seed remain to be studied. Empfindlichkeit von Kulturpflanzenbeständen gegenüber einer Erhöhung der ultravioletten Einstrahlung unter nördlichen Wachstumsbedingungen Kulturpflanzenbestände, die unter hohen Breitengraden wachsen, sind an geringe Intensitäten der solaren ultravioletten B Einstrahlung (UV-B) angepasst. Aufgrund der Destruktion der Stratosphäre, insbesondere der Ozonschicht, im Bereich der polaren Gebiete der Erde, ist eine zunehmende Intensität der UV-B Strahlung in hohen Breitengraden festzustellen. Um die Konsequenzen einer Erhöhung von UV-B auf Kulturpflanzenbestände zu bestimmen, wurde die Empfindlichkeit unterschiedlicher Arten wie Gerste, Weizen, Hafer, Klee, Wiesenlieschgras, Wiesenschwingel, Rohrschwingel und Kartoffel in Jokioinen, Finnland, untersucht. Das Experiment wurde im Felde durchgeführt unter natürlichen Lichtbedingungen mit einer kontinuierlichen Zunahme von 30 % für UV-B. Sowohl eine Erhöhung der UV-B als auch die Kontrolle mit leicht erhöhten UV-B Strahlungen beeinflussten die Anzahl der Nebenwurzeln bei den Getreidepflanzen und die spezifische Blattfläche sowie den Gehalt an phenolischen Substanzen bei den Gräsern. Die Wirkungen variierten entsprechend der Pflanzenvarietät und der Anbauzeit. Allerdings wurden keine erkennbare Schädigungen noch Änderungen in der Biomasse und in der Ertragsproduktion bei einer der untersuchten Pflanzenbestände gefunden. Langzeitwirkungen auf die genetische bedingte Stabilität und Keimung der Kulturpflanzen sollte weiterhin untersucht werden. [source]

Inner-crown Microenvironments of Two Emergent Tree Species in a Lowland Wet Forest,

BIOTROPICA, Issue 2 2005
Catherine L. Cardelús
ABSTRACT Vascular epiphyte communities, comprising up to 25 percent of tropical forest flora, contribute to plant diversity and thus ecosystem-level processes; however, one of the proximal determinants of those communities, microclimate, is little studied. Here we present the first comprehensive study of microclimates in the inner crowns of two emergent tree species, Hyeronima alchorneoides and Lecythis ampla, at La Selva Biological Station, Costa Rica. We examined photon flux density, temperature, vapor pressure, and humidity in inner-crown branches during the wet and dry seasons and during the wet-season leafless phase of Lecythis. In both seasons, the percentage daily PFD in foliated Lecythis crowns (9%, wet season; 11%, dry season) was significantly higher than in Hyeronima crowns (5%, both seasons), with the leafless wet-season PFD of Lecythis reaching 23 percent of full sun. Temperature and vapor pressure varied less in Hyeronima than in Lecythis crowns during the dry season. Microenvironmental conditions for epiphytes within Hyeronima crowns were more spatially and temporally homogeneous and were more buffered from ambient conditions than within Lecythis crowns. Growing conditions within the crowns of the same trees and among different trees were measurably different and are likely to affect the structure and composition of the resident epiphyte communities. RESUMEN Las epífitas vasculares representan el 25 por ciento de la flora vascular en bosques tropicales. Sin embargo, existe poca información sobre el microclima en que estas plantas habitan. Comparamos flujo fotosintético (PFD), temperatura, presión de vapor y humedad en las ramas interiores de dos especies de árboles emergentes, Hyeronima alchorneoides y Lecythis ampla, en la Estación Biológica La Selva, Costa Rica. En cada estación, se encontró una diferencia significativa entre el por ciento PFD en el dosel de Lecythis (9%, estación lluviosa; 11%, estación seca) y el por ciento PFD registrado en Hyeronima (5.6%, los dos estaciones), con por ciento PFD de Lecythis en la época sin hojas llegando a 23 por ciento. Las copas de Hyeronima mostraron menos variación en temperatura y presión de vapor que las copas de Lecythis durante la época seca. El microclima en el dosel de Hyeronima fue más homogéneo espacialmente y temporalmente y más regulado en comparación con el microclima en Lecythis. Las condiciones de crecer en el dosel de un árbol y entre diferentes árboles son diferentes, y probablemente afectan la estructura y composición de las comunidades de epífitas. [source]

Is heterosis in maize mediated through better water use?

NEW PHYTOLOGIST, Issue 2 2010
José Luis Araus
Summary ,Heterosis increases yield potential and improves adaptation to stress in maize (Zea mays); however, the underlying mechanisms remain elusive. ,A set of tropical inbred lines and their hybrids were grown in the field for 2 yr under three different water regimes. First-year plant water use was evaluated by measuring instantaneous traits (stomatal conductance (gs) and steady-state chlorophyll fluorescence (Fs)) in individual leaves together with time-integrative traits, which included mineral accumulation in the whole leaves of plants and oxygen isotope enrichment above source water (,18O) and carbon isotope discrimination (,13C) in the same pooled leaves and in mature kernels. Second-year water use was evaluated by measuring leaf temperature, gs and relative water content (RWC). ,Within each growing condition, hybrids showed higher Fs, mineral accumulation, RWC, and lower leaf temperature, ,18O and ,13C than inbred lines. Therefore, hybrids had a better water status than inbred lines, regardless of the water conditions. Differences in grain yield across growing conditions were explained by differences in water-use traits, with hybrids and inbred lines following a common pattern. Within each growing condition, most variations in grain yield, between hybrids and inbred lines, were also explained by differences in plant water-use traits. ,Heterosis in tropical maize seems to be mediated by improved water use, irrespective of the water conditions during growth. [source]

Will photosynthesis of maize (Zea mays) in the US Corn Belt increase in future [CO2] rich atmospheres?

GLOBAL CHANGE BIOLOGY, Issue 6 2004
An analysis of diurnal courses of CO2 uptake under free-air concentration enrichment (FACE)
Abstract The C4 grass Zea mays (maize or corn) is the third most important food crop globally in terms of production and demand is predicted to increase 45% from 1997 to 2020. However, the effects of rising [CO2] upon C4 plants, and Z. mays specifically, are not sufficiently understood to allow accurate predictions of future crop production. A rainfed, field experiment utilizing free-air concentration enrichment (FACE) technology in the primary area of global corn production (US Corn Belt) was undertaken to determine the effects of elevated [CO2] on corn. FACE technology allows experimental treatments to be imposed upon a complete soil,plant,atmosphere continuum with none of the effects of experimental enclosures on plant microclimate. Crop performance was compared at ambient [CO2] (354 , mol mol,1) and the elevated [CO2] (549 ,mol mol,1) predicted for 2050. Previous laboratory studies suggest that under favorable growing conditions C4 photosynthesis is not typically enhanced by elevated [CO2]. However, stomatal conductance and transpiration are decreased, which can indirectly increase photosynthesis in dry climates. Given the deep soils and relatively high rainfall of the US Corn Belt, it was predicted that photosynthesis would not be enhanced by elevated [CO2]. The diurnal course of gas exchange of upper canopy leaves was measured in situ across the growing season of 2002. Contrary to the prediction, growth at elevated [CO2] significantly increased leaf photosynthetic CO2 uptake rate (A) by up to 41%, and 10% on average. Greater A was associated with greater intercellular [CO2], lower stomatal conductance and lower transpiration. Summer rainfall during 2002 was very close to the 50-year average for this site, indicating that the year was not atypical or a drought year. The results call for a reassessment of the established view that C4 photosynthesis is insensitive to elevated [CO2] under favorable growing conditions and that the production potential of corn in the US Corn Belt will not be affected by the global rise in [CO2]. [source]

A model for optimisation of water management in rice polders in Thailand,

IRRIGATION AND DRAINAGE, Issue 5 2005
Preecha Wandee
modèle mathématique; polders de riz; polder système de gestion de l'eau; optimisation Abstract This paper presents a mathematical model for the determination of optimal values for the main components of water management systems in rice polders in Thailand. The aim of the water management system in a rice area is to create good growing conditions for the crops. Under the hydrological conditions of Thailand the average rainfall during the rainy season is more than enough for growing rice or other crops. However, during the dry season there is a very small amount of rainfall. Thus the farmers are confronted with two quite different conditions and water management has to deal with irrigation and drainage issues. The main components of the water management system in a rice polder are the water level in the canals, the percentage of open surface water, discharge capacity from the field and discharge capacity of the pumping station or sluice. A model has been developed that takes into account damage due to flooding and drought as well as construction and maintenance cost for irrigation and drainage systems based on the hydrological conditions. Optimising of such a water management system means determining the main components in such a way that the equivalent annual costs are minimal. A case study has been done for a rice polder in Suphanburi province. It was found that the polder water level for rice under rainfed conditions could be kept above ground level to minimise loss of water from the rice field, whereas under irrigated conditions the polder water level has to be kept below ground level to get good drainage conditions. Copyright © 2005 John Wiley & Sons, Ltd. Cet article présente un modèle mathématique pour l'optimisation des composants principaux du système de gestion de l'eau dans des polders de riz en Thaïlande. Le but du système de gestion de l'eau dans un secteur de riz est de créer de bonnes conditions de croissance pour les récoltes. Dans la situation hydrologique de la Thaïlande les précipitations moyennes pendant la saison des pluies sont plus que suffisantes pour cultiver du riz croissant ou d'autres récoltes. Cependant, durant la saison sèche il y a très peu de précipitations. Ainsi les fermiers sont confrontés à deux conditions tout à fait différentes. Par conséquent la gestion de l'eau doit prendre en compte des problèmes d'irrigation et de drainage. Les composants principaux du système de gestion de l'eau dans un polder de riz sont le niveau d'eau dans les canaux, le pourcentage de l'eau ouverte, la capacité de décharge du champ et capacité de décharge de la station de pompage ou d'écluse. On a développé un modèle qui tient compte des dommages dus à l'inondation et à la sécheresse aussi bien que du coût de construction et d'entretien pour l'irrigation et à la canalisation basée sur les conditions hydrologiques. La linéarisation d'un tel système de gestion de l'eau implique de déterminer les composants principaux de telle manière que le système entier ait le coût équivalent annuel minimum. Une étude de cas a été faite pour un polder de riz dans la province de Suphanburi. On a constaté que le niveau d'eau du polder pour le riz irrigué à l'eau de pluie pouvait être gardé au-dessus du niveau du sol pour réduire au minimum la perte d' eau de la rizière, tandis que dans des conditions irriguées le niveau d'eau de polder doit être gardé au-dessous du niveau du sol pour obtenir de bonnes conditions de drainage. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Response of beech (Fagus sylvatica) to elevated CO2 and N: Influence on larval performance of the gypsy moth Lymantria dispar (Lep., Lymantriidae)

JOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2001
M. W. Henn
Two-year-old beech seedlings were kept from germination to bioassays with Lymantriadispar under the following conditions: ambient CO2/low N, elevated CO2/low N, ambient CO2/elevated N, and elevated CO2/elevated N. The effect of these growing conditions of the trees on the performance of the defoliator L. dispar was studied 2 years after initiating the tree cultivation. The developmental success of third-instar larvae of L. dispar was characterized by the weight gained, percentage of weight gain, relative growth rate (RGR), relative consumption rate (RCR), and efficiency of conversion of ingested food into body substance (ECI). Contrary to our expectations, additional N-fertilization did not increase and elevated CO2 did not delay larval growth rate. However, the environmental treatments of the beech seedlings were found to affect the larval performance. Larvae consumed significantly higher amounts of foliage (RCR) on beech trees under controlled conditions (ambient CO2 and low N) compared to those under elevated CO2 and enhanced N. The opposite was true for ECI. The lowest efficacy to convert consumed food to body substance was observed under control conditions and the highest when the larvae were kept on beech trees grown under elevated CO2 and additional N-fertilization. These opposite effects resulted in the weight gain-based parameters (absolute growth, percentage of growth, and RGR) of the gypsy moth larvae remaining unaffected. The results indicate that the gypsy moth larvae are able to change their ECI and RCR to obtain a specific growth rate. This is discussed as an adaptation to specific food qualities. [source]

Global patterns in plant height

JOURNAL OF ECOLOGY, Issue 5 2009
Angela T. Moles
Summary 1. ,Plant height is a central part of plant ecological strategy. It is strongly correlated with life span, seed mass and time to maturity, and is a major determinant of a species' ability to compete for light. Plant height is also related to critical ecosystem variables such as animal diversity and carbon storage capacity. However, remarkably little is known about global patterns in plant height. Here, we use maximum height data for 7084 plant Species × Site combinations to provide the first global, cross-species quantification of the latitudinal gradient in plant height. 2. ,The mean maximum height of species growing within 15° of the equator (7.8 m) was 29 times greater than the height of species between 60° and 75° N (27 cm), and 31 times greater than the height of species between 45° and 60° S (25 cm). There was no evidence that the latitudinal gradient in plant height was different in the northern hemisphere than in the southern hemisphere (P = 0.29). A 2.4-fold drop in plant height at the edge of the tropics (P = 0.006) supports the idea that there might be a switch in plant strategy between temperate and tropical zones. 3. ,We investigated 22 environmental variables to determine which factors underlie the latitudinal gradient in plant height. We found that species with a wide range of height strategies were present in cold, dry, low productivity systems, but there was a noticeable lack of very short species in wetter, warmer, more productive sites. Variables that capture information about growing conditions during the harsh times of the year were relatively poor predictors of height. The best model for global patterns in plant height included only one term: precipitation in the wettest month (R2 = 0.256). 4. ,Synthesis. We found a remarkably steep relationship between latitude and height, indicating a major difference in plant strategy between high and low latitude systems. We also provide new, surprising information about the correlations between plant height and environmental variables. [source]

Reduced reproductive success and offspring survival in fragmented populations of the forest herb Phyteuma spicatum

JOURNAL OF ECOLOGY, Issue 6 2005
ANNETTE KOLB
Summary 1Habitat fragmentation, which reduces the size and increases the isolation of populations, is a major threat to biodiversity. For Phyteuma spicatum, a self-incompatible, rare understorey herb in deciduous forests of north-western Germany, I tested the hypotheses that: (i) fitness (in terms of reproductive success) is reduced in small or isolated populations, (ii) reproduction in small populations is reduced by pollen limitation and (iii) genetic effects cause fitness reductions in small populations. 2I compared the reproductive success of plants of Phyteuma in 14 populations of different size and degree of isolation. Seed production was, as predicted, positively related to population size but was also influenced by plant size, although not by population isolation, density or habitat quality. 3I performed supplemental hand-pollinations in 10 of the 14 populations using pollen from the same population (test for pollen quantity) or from another large population (pollen quality). The proportional difference in seed production between hand-pollinated plants and open-pollinated controls increased with decreasing population size, indicating pollinator limitation of reproduction in small populations. There was no difference between the two hand-pollination treatments, suggesting that a sufficient number of cross-compatible mates was available even in the smallest populations. 4Progeny from the 14 populations were grown for 32 weeks in a common environment. There was no effect of population size on germination, but final seedling survival was positively related to population size, and this relationship was more pronounced in the glasshouse than under more favourable growing conditions in a common garden. Genetic effects may thus reduce fitness (here measured in terms of survival) in plants from small populations, making them more susceptible to environmental stress. 5The results suggest that both reproduction and offspring performance may be reduced in small populations even of long-lived species such as Phyteuma spicatum. Different processes, such as pollen limitation and genetic deterioration, may interact and affect local population dynamics and the persistence of species in fragmented landscapes. [source]

The genetic basis of early-life morphological traits and their relation to alternative male reproductive tactics in Atlantic salmon

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2010
D. J. PáEZ
Abstract Although heritability estimates for traits potentially under natural selection are increasingly being reported, their estimation remains a challenge if we are to understand the patterns of adaptive phenotypic change in nature. Given the potentially important role of selection on the early life phenotype, and thereby on future life history events in many fish species, we conducted a common garden experiment, using the Atlantic salmon (Salmo salar L.), with two major aims. The first objective is to determine how the site of origin, the paternal sexual tactic and additive genetic effects influence phenotypic variation of several morphological traits at hatching and emergence. The second aim is to test whether a link exists between phenotypic characteristics early in life and the incidence of male alternative tactics later in life. We found no evidence of a site or paternal effect on any morphological trait at hatching or emergence, suggesting that the spatial phenotypic differences observed in the natural river system from which these fish originated are mainly environmentally driven. However, we do find significant heritabilities and maternal effects for several traits, including body size. No direct evidence was found correlating the incidence of precocious maturation with early life characteristics. We suggest that under good growing conditions, body size and other traits at early developmental stages are not reliable cues for the surpassing of the threshold values associated with male sexual development. [source]

Carotenoids in pungent and non-pungent peppers at various developmental stages grown in the field and glasshouse,

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2002
M Russo
Abstract Carotenoids in edible portions of plants can provide health benefits to humans. How growing conditions affect levels of carotenoids in pepper fruits as they mature is not well known. Five cvs of bell pepper (Bell Captain, Melody, North Star, Ranger, Red Beauty) and five cvs of pungent-type peppers (Anaheim, Ancho, Cayenne, Pimento, Red Cherry) were grown in a glasshouse and in the field. Fruits were harvested at the green, turning (50% green) and mature red stages and analysed for levels of the carotenoids ,-cryptoxanthin, ,-carotene, ,-carotene, capsanthin, lutein and zeaxanthin and totals of these carotenoids. Levels of provitamin A: retinol equivalents (RE) were derived from levels of ,-cryptoxanthin, ,-carotene and ,-carotene. Levels of most carotenoids and RE were significantly higher in glasshouse-grown plants, and most were higher in fruits at the red stage. Fruits of Ancho type had the most ,-cryptoxanthin, ,-carotene, ,-carotene, total carotenoids and RE, while fruits of Red Cherry type had the most capsanthin and zeaxanthin, and fruits of Bell Captain had the most lutein. Interactions of the main effects variables, ie location of production (field vs glasshouse), stage of development and cultivar, indicated differences in patterns of carotenoid levels and RE. The data indicated that growing conditions influenced carotenoid levels. The more consistent and protected conditions in the glasshouse may have caused carotenoid levels to be increased, especially at the red stage. Published in 2002 for SCI by John Wiley & Sons, Ltd [source]

Is heterosis in maize mediated through better water use?

The influence of species and growing conditions on the 18-O enrichment of leaf water and its impact on ,effective path length'

NEW PHYTOLOGIST, Issue 3 2009
Ansgar Kahmen
Summary ,,The stable oxygen isotope ratio (,18O) of plant material has been shown to contain essential information on water and carbon fluxes at the plant and ecosystem scales. However, the effective path length (Lm), a parameter introduced to leaf-water models still requires a comprehensive biological characterization to allow interpretation of ,18O values in plant material with confidence. ,,Here, we tested the variability of Lm across and within three species that developed leaves in environments with different relative humidity. We also tested whether the Lm of fully developed leaves is affected by short-term fluctuations in relative humidity. ,,We determined that significant differences in Lm exist among Phaseolus vulgaris, Rizinus communis and Helianthus annuus. Within a given species, however, Lm values did not differ significantly among individuals. ,,These findings indicate that Lm is species specific and a relatively constant parameter and that Lm will not obscure the interpretation of ,18O values in plant material of a given species. We urge caution, however, because values for Lm are derived from fitting leaf-water models to measured values of ,18O, so care must be taken in assigning a ,cause' to values of Lm as they likely capture a combination of different biological leaf properties [source]

Small-scale variation in growing season length affects size structure of scarlet monkeyflower

OIKOS, Issue 1 2004
Jennifer L. Williams
Growing season length can control plant size over altitudinal and biogeographic scales, but its effect at the scale of meters is largely unexplored. Within the riparian zone of a northern California river, scarlet monkeyflower, Mimulus cardinalis, grows significantly larger at sites high in the channel as compared to sites low in the channel, and even larger where tributaries meet the main stem of the river. We explored the hypothesis that markedly different growing season length controls this size variation. Due to the very gradual retreat of the water level following winter flooding, emergence time is three months longer for plants growing at tributary confluences than for plants growing at low elevations in the channel. Consistent with the growing season length hypothesis, we found no difference in transplant growth between river and tributary confluence sites in an experiment where we equalized growing season length at these locations. Moreover, a second experiment showed that individuals planted earlier in the year gain a distinct size advantage over those planted later, even though growing conditions are less ideal. These results suggest that emergence time may be a key determinant of plant size structure along rivers, an important result considering forecasted variation in water flows with climate change. [source]

On the elastic contribution to crystal growth in complex environments

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2005
A. Gadomski
Abstract Based on a number of experimental studies, we propose to consider how elastic interactions between a crystal and its surroundings change crystal growing conditions. To aim to do this, we analyze the influence of some nonequilibrium modification of the Gibbs,Thomson thermodynamic condition, prescribed at the crystal boundary, on some properties of a kinetic model of protein crystal growth in a mass-convection regime. Next, to draw the physical picture more realistically, we study the influence of a certain stochastic perturbation on the crystal growth rate. To fulfill the task we apply the description of crystal growth in terms of nonequilibrium thermodynamics at a mesoscopic level. The proposed model offers a quite comprehensive picture of the formation of modern organic crystalline materials such as non-Kossel crystals. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Over-expression of a Populus peroxisomal ascorbate peroxidase (PpAPX) gene in tobacco plants enhances stress tolerance

PLANT BREEDING, Issue 4 2009
Y-J. Li
Abstract Ascorbate peroxidase (APX) plays an important role in the metabolism of hydrogen peroxide in higher plants. We studied the effect of over-expressing a Populus peroxisomal ascorbate peroxidase (PpAPX) gene under the control of the cauliflower mosaic virus 35S promoter or the rd29 promoter in transgenic tobacco. High levels of PpAPX gene expression were observed in 35S-PpAPX transgenic plants, with a 50% increase in APX activity. The constitutive expression of PpAPX in the tobacco exhibited no morphological abnormalities, while significantly increased root growth was observed in transgenic plants, when compared to control plants. Several independently transformed lines were propagated and evaluated for resistance to methyl viologen (MV), drought and salt stress. Visual assessment of transgenic and control lines exposed to MV (50 or 100 ,mol) confirmed that over-expression of APX minimized leaf damage. APX activity was nearly 80% higher in the leaves of transgenic plants in response to drought or salt stresses. Moreover, the transgenic tobacco also showed significantly improved drought resistance and salt tolerance at the vegetative stage. RNA blot analysis indicated that the PpAPX transcript level was very low under normal growing conditions in rd29Ap-PpAPX plants, but clearly increased under drought stress. Our results show that PpAPX does not play a significant role under normal growing conditions, but did ameliorate oxidative injury under abiotic stress. The Ad29 promoter should be used as an inducible promoter in transgenic works. [source]

Genotypic and temperature effects on wheat grain yield and quality in a hot irrigated environment

PLANT BREEDING, Issue 4 2006
I. S. A. Tahir
Abstract High temperature influences both grain yield and end-use quality of wheat. The objectives of this study were to evaluate the performance of selected wheat genotypes under heat stress and to examine the effects of high temperatures during grain filling on grain yield and end-use quality parameters. Fifteen bread wheat genotypes in 2000/2001 and 18 genotypes in 2002/2003 were evaluated under the optimum and late-sowing conditions of the irrigated hot environment of the Gezira Research Farm, Wad Medani, Sudan. The genotypes comprised released varieties and elite lines from the Sudanese wheat improvement programme. Data collected included grain yield, grain weight and grain end-use quality including protein content, protein composition, SDS sedimentation values (SDSS) and gluten strength as determined by mixograph analyses. High temperatures significantly decreased grain yield by decreasing grain weight. Although genotypes exhibited variation in magnitude of response, results indicated that high temperature during grain filling increased both soluble and insoluble protein contents, SDSS, mixograph peak height (MPH) and the descending slope at 2 min past peak (MDS). In contrast, mixograph peak time (MPT) and the curve width at 2 min past peak (MCW) were significantly decreased. Flour protein correlated positively with SDSS, MPH and MDS and negatively with MCW. MPT correlated negatively with MDS and positively with MCW. Results indicate that high temperature increased both soluble and insoluble protein contents, SDSS and MPH, and hence the gluten strength, but decreased flour mixing time and tolerance and hence the dough elasticity. Variation observed among genotypes suggests that grain end-use quality could be improved under high temperature conditions utilizing the available variability; however, it might require evaluation under various growing conditions. [source]

Can improvement in photosynthesis increase crop yields?

PLANT CELL & ENVIRONMENT, Issue 3 2006
STEPHEN P. LONG
ABSTRACT The yield potential (Yp) of a grain crop is the seed mass per unit ground area obtained under optimum growing conditions without weeds, pests and diseases. It is determined by the product of the available light energy and by the genetically determined properties: efficiency of light capture (,i), the efficiency of conversion of the intercepted light into biomass (,c) and the proportion of biomass partitioned into grain (,). Plant breeding brings , and ,i close to their theoretical maxima, leaving ,c, primarily determined by photosynthesis, as the only remaining major prospect for improving Yp. Leaf photosynthetic rate, however, is poorly correlated with yield when different genotypes of a crop species are compared. This led to the viewpoint that improvement of leaf photosynthesis has little value for improving Yp. By contrast, the many recent experiments that compare the growth of a genotype in current and future projected elevated [CO2] environments show that increase in leaf photosynthesis is closely associated with similar increases in yield. Are there opportunities to achieve similar increases by genetic manipulation? Six potential routes of increasing ,c by improving photosynthetic efficiency were explored, ranging from altered canopy architecture to improved regeneration of the acceptor molecule for CO2. Collectively, these changes could improve ,c and, therefore, Yp by c. 50%. Because some changes could be achieved by transgenic technology, the time of the development of commercial cultivars could be considerably less than by conventional breeding and potentially, within 10,15 years. [source]

Expression of resistance to Leptosphaeria maculans in Brassica napus double haploid lines in France and Australia is influenced by location

ANNALS OF APPLIED BIOLOGY, Issue 2 2008
R. Delourme
Abstract Blackleg, caused by Leptosphaeria maculans, is a major disease of oilseed rape (Brassica napus), worldwide, including Australia and France. The aims of these studies were first, to determine if higher levels of resistance to L. maculans could be generated in double haploid (DH) lines derived from spring-type B. napus cv. Grouse, which has a good level of field resistance to blackleg; and second, to determine whether the resistance to blackleg disease of individual DH lines responds differentially to different L. maculans field populations within and between the two countries. DH lines were extracted from cv. Grouse and tested in field experiments carried out in both France and Australia against natural L. maculans populations. Extracting and screening DH lines were an effective means to select individual lines with greatly improved expression of resistance to blackleg crown canker disease in comparison with the original parental population. However, relative disease resistance rankings for DH lines were not always consistent between sites. The higher level of resistance in France was shown to be because of a high expression level of quantitative resistance in the French growing conditions. Big differences were observed for some DH lines between the 2004 and the 2005 field sites in Australia where the L. maculans populations differed by their virulence on single dominant gene-based resistant lines derived from Brassica rapa ssp. sylvestris. This differential behaviour could not be clearly explained by the specific resistance genes until now identified in these DH lines. This investigation highlights the potential to derive DH lines with superior levels of resistance to L. maculans compared with parental populations. However, in locations with particularly high pathogen diversity, such as in southern Australia, multiyear and multisite evaluations should be performed to screen for the most efficient material in different situations. [source]

Using plant traits to compare sward structure and composition of grass species across environmental gradients

APPLIED VEGETATION SCIENCE, Issue 1 2004
M. Duru
Abstract. Plant traits which may give an indication of a plant's strategy for nutrient acquisition and regeneration are known for numerous grassland species. This study aimed to establish whether there is any relationship between two plant traits: specific leaf area (SLA) and number of reproductive tillers, and sward structural characteristics which influence herbage intake by grazers (bulk density and digestibility, leaf:stem ratio). Comparison is made for nutrient-rich (Dactylis glomerata) and nutrient-poor (Festuca rubra) grass species. We hypothesized that these traits are responsive to environmental gradients and also act on the processes of the ecosystem. Both grasses were compared with two P-fertilizer rates in two localities (200 and 1300 m a.s.l.) which differed in their temperature:radiation ratios. For the vegetative phase SLA was well correlated with sward characteristics: D. glomerata, which has the higher SLA, has the lower bulk density and higher digestibility. The values of SLA and vegetation bulk density varied according to growing conditions (P-rate and temperature:radiation ratio), but the ranking of the species remained the same because the phenotypic plasticity that exists for plant traits was also observed for sward structure and composition. That suggested the possibility of grouping natural grassland species for their relevant characteristics for grazers according to SLA values. Over the reproductive phase, the proportion of stems was well correlated to the percentage of reproductive tillers. However, the percentage of reproductive tillers was a very plastic trait for both species, depending on the growing conditions, and resulting in a density-dependent effect, particularly for F. rubra. The species studied were too plastic and too similar in their regenerative strategy so that there is no unique relationship between percentage of reproductive tillers and stem proportion, regardless of the species and the growing conditions. The number of reproductive tillers is not a suitable plant trait which could be used to rank species for leaf and stem proportions in the sward. [source]

Mild stress during development affects the phenotype of great tit Parus major nestlings: a challenge experiment

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010
WILLEM TALLOEN
Conditions experienced during early development may affect both adult phenotype and performance later during life. Phenotypic traits may hence be used to indicate past growing conditions and predict future survival probabilities. Relationships between phenotypic markers and future survival are, however, highly heterogeneous, possibly because poor- and high-quality individuals cannot be morphologically discriminated when developing under good environmental conditions. Sub-optimal breeding conditions, in contrast, may unmask poor-quality individuals in a measurable way at the morphological level. We thus predict stronger associations between phenotype and performance under stress. In this field study, we test this hypothesis, experimentally challenging the homeostasis of great tit (Parus major) nestlings by short-term deprivation of parental care, which had no immediate effect on nestling fitness. The experiment was replicated during two subsequent breeding seasons with contrasting ambient weather conditions. Experimental (short-term) stress affected tarsus growth but not residual mass at fledging, whereas ambient (continuous) stress affected residual mass but not tarsus growth. Short-term stress effects on tarsus length and tarsus fluctuating asymmetry were only apparent when ambient conditions were unfavourable. Residual mass and hatching date, but none of the other phenotypic traits, predicted local survival, whereby the strength of the relationship did not vary between both years. Because effects of stress on developmental homeostasis are likely to be trait-specific and condition-dependent, studies on the use of phenotypic markers for individual fitness should integrate multiple traits comprising different levels of developmental complexity. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 103,110. [source]