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271.
BUALUANG FAIYUE CHENNIAPPAN VIJAYALAKSHMI SHAFQAT NAWAZ YASUO NAGATO SHIN TAKETA MASAHIKO ICHII MOHAMMED J. AL‐AZZAWI TIMOTHY J. FLOWERS 《Plant, cell & environment》2010,33(5):687-701
An apoplastic pathway, the so‐called bypass flow, is important for Na+ uptake in rice (Oryza sativa L.) under saline conditions; however, the precise site of entry is not yet known. We report the results of our test of the hypothesis that bypass flow of Na+ in rice occurs at the site where lateral roots emerge from the main roots. We investigated Na+ uptake and bypass flow in lateral rootless mutants (lrt1, lrt2), a crown rootless mutant (crl1), their wild types (Oochikara, Nipponbare and Taichung 65, respectively) and in seedlings of rice cv. IR36. The results showed that shoot Na+ concentration in lrt1, lrt2 and crl1 was lower (by 20–23%) than that of their wild types. In contrast, the bypass flow quantified using trisodium‐8‐hydroxy‐1,3,6‐pyrenetrisulphonic acid (PTS) was significantly increased in the mutants, from an average of 1.1% in the wild types to 3.2% in the mutants. Similarly, bypass flow in shoots of IR36 where the number of lateral and crown roots had been reduced through physical and hormonal manipulations was dramatically increased (from 5.6 to 12.5%) as compared to the controls. The results suggest that the path of bypass flow in rice is not at the sites of lateral root emergence. 相似文献
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The role of competition in structuring animal communities iscurrently hotly debated. One of the crucial assumptions underlyingthe concept of resource partitioning as a function of competitionis the jack-of-all-trades, master of none principle: differencesin morphology and behavior results in the different abilitiesto use different resources and hence results in the potentialto partition those resources. Examination of the manner by whichhabitat structure constrains resource use offers a mechanisticapproach to study community structure. Anolis lizards providea useful example to illustrate the approach since in the WestIndies they show consistent assemblages of ecomorphs from islandto island. The bases for a strong influence of habitat structureon the resource use pattern of anoles are reviewed as a preambleto a new analysis of the 2-species Anolis assemblages in theLesser Antilles. The two species on the island of Grenada showa strong morphological segregation associated with differentuse patterns of similar microhabitats. The two species on St.Kitts in a richer habitat show strong microhabitat segregationbut little morphological difference apart from size. A relatedpair of species on Antigua in a habitat similar to that on Grenadaappear to be constrained in the degree of habitat segregationand, perhaps as a consequence, show morphological segregationsimilar to that documented for the species on Grenada. Thesecomparisons provide further evidence of the strong influenceof habitat structure on the morphology and habitat partitioningpatterns of coexisting species. Field and experimental studiesof coexisting bird assemblages suggest that details of habitatstructure also have a strong influence on their morphology andresource use patterns. Studies focusing on the manner by whichanimals use different microhabitats provide a useful, mechanisticapproach to study the influence of competition on communitystructure 相似文献
274.
SALLY A. ENTREKIN JENNIFER L. TANK EMMA J. ROSI-MARSHALL TIMOTHY J. HOELLEIN GARY A. LAMBERTI 《Freshwater Biology》2008,53(8):1642-1657
1. Additions of large wood are being used to restore streams that have been subjected to channelization, wood removal or riparian timber harvest. This added wood potentially increases channel stability, habitat complexity and organic matter retention and improves habitat and productivity of higher trophic levels. However, few stream restorations monitor restoration effectiveness after project completion. 2. We added 25 aspen logs (each 2.5 m length × 0.5 m diameter) to 100‐m reaches of each of three forested headwater streams in the Upper Peninsula of Michigan, U.S.A. These wood‐poor streams drain forests that were completely harvested of timber over a century ago and have been selectively logged for the past 50–60 years. An upstream unmanipulateds 100‐m reach in each stream served as the control. 3. We evaluated responses in organic matter processing by measuring red maple leaf decomposition 1 year before and 2 years after wood addition. We also quantified coarse organic matter standing stocks in the main channel and in debris accumulations associated with large wood. In response to wood addition, we predicted both organic matter standing stocks and leaf decomposition rates would increase, thereby enhancing resource availability to higher trophic levels. 4. Leaf decomposition rates did not change following wood addition. Temporal variation in rates among streams was mostly explained by differences in degree days, water velocity, scour/burial and water column inorganic nitrogen concentrations, but not large wood. Variation within streams across years was explained by differences in degree days, water velocity and shredder biomass. 5. Contrary to our prediction, organic matter standing stocks did not increase significantly at the reach scale. However, the experimentally added wood retained c. 4% of total annual coarse benthic organic matter (CBOM) in the first year and an additional c. 15% in the second year, suggesting accumulation over time in the manipulated reaches. The CBOM held by the new logs may be more biologically available because it is less susceptible to burial and transport than material in the streambed. 6. Some shredding macroinvertebrates responded to changes caused by the wood additions. In particular, the common caddisfly shredder, Lepidostoma sp., increased in abundance in leaf bags following wood addition, whereas the biomass of the winter stoneflies, Capniidae, declined in the first year. 7. Considerable funds are spent to restore in‐stream habitat, but few restorations are monitored, particularly over long periods (>5 years). Our results show that longer‐term monitoring is needed to determine the efficacy of these restorations on ecosystem function; organic matter decomposition in our low‐gradient streams did not respond to a substantial increase in large wood after 2 years. 相似文献
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Samples of up to ten study skins for each of five species of Microhierax , two species of Polihierax , one species of Spiziapteryx and 23 species of small Falco were measured for 24 dimensions of the head, wings, tail and feet. The logarithmic (log10 ) valucs of the means of each mcasurcmcnt for each species, and for each sex where dimorphic, were compared using cluster and factor analyses. Microhierux falconets are most similar to the African Pygmy Falcon Polihierax sernitorquatus but are morphometrically distinct from all other falconets and small Falco species. The five species of Microhierax falconets are morphometrically similar, sexually dimorphic and probably replace one another ecologically, since all are allopatric or differ in proportions and habitat where parapatric (two species). Prelim[nary observatioris on the hunting behaviour and social organization of the Rlack-thighed Falconet Microhierux fringillarius indicate that the genus has morphological and social specializations for aerial capture of large forest insects. 相似文献
280.
With the overall goal of developing a method to reliably induce
ovipositionin the freshwater pulmonate Biomphalaria
glabrata, the effectsof water quality on female reproductive
physiology were examined.Groups of snails were subjected to
controlled experimental conditionsconsisting of a daily regimen of
feeding and water change. Aftera period of acclimatiz-ation, egg mass
(EM) output under theseconditions was relatively stable, and snails
laid a majority(82.5%) of their EM during the initial 4 h following
daily waterchange. When this regimen was perturbed by halting water
changefor 24 h (dirty-water treatment), EM output was significantly
inhibited.When water change was resumed, EM output returned to
previouslevels within 4 h post-water change (PWC). This dirty-water
treatmentfollowed by water change also resulted in a significant
increasein mean EM size during the 4 h PWC when compared to
controls.To better describe the events preceding egg-laying in
B. glabrata,we then used these experimental manipulations to
induce ovipositionin groups of snails, and dissected them during the
4 h followingwater change. Observations of the reproductive tracts of
stimulatedsnails allowed us to divide the egg-laying process, from
ovulationto oviposition, into discrete stages, after de Jong-Brink,
Koop,Roos & Bergamin-Sassen (1982). Stage I was characterized bythe
presence of ova in the hermaphroditic duct and carrefour,and
fertilized, packaged eggs in the oviduct and muciparousgland. Stage
II was characterized by the presence of packagedeggs in the othecal
gland embedded in a mucous layer, constitutingthe egg mass to be laid
on the substratum. No packaging eventswere occurring in the
carrefour/albumen gland region duringthis stage. When snails were
dissected immediately after oviposition(Stage III), unpackaged ova
were observed in the hermaphroditicduct, carrefour, and oviduct. The
mean time it took for snailsto reach Stage III was 120 6 49 min (SD),
and this value wasstatistically different from the mean time to
Stages I and II,showing that our induction protocol results in a
temporal progressionthrough the egg- laying process. Gonadal oocyte
density (oocytes/mm2of ovotestis) was quantified as a
function of these stages ofthe reproductive cycle, and was found to
be significantly lowerduring Stage II (fully formed egg mass in
othecal gland) thanall other stages examined. Taken together, these
results showthat female reproductive activity can be experimentally
controlledthrough the manipulation of water quality, and that such a
protocolis a valuable tool for addressing specific questions
regardingthe reproductive physiology of B. glabrata. The
implicationsof these results as they pertain to the regulation of
femalereproductive activity in B. glabrata are discussed. (Received 15 January 1999; accepted 17 May 1999) 相似文献