The ecology of a beech forest on Mt. Sanpoiwadake,Hakusan National Park,Japan II. The correlation of the subassociation within the Lindero membranaceae-fagetum crenatae association and environmental parameters

Detailed examination of a sample plot covered by the Lindero membranaceae-Fagetum crenatae association on Mt. Sanpoiwadake, Hakusan National Park, revealed a number of correlations between the distribution of subassociations and environmental factors. The subassociations on the south-facing slopes receive deep snow cover in winter with rapid melting in the spring. They occur on porous, freely draining soils, typical of the general range of brown forest soils. Conversely, on the north-eastern slopes there are widespread late-snow patches which delay leaf development and expansion and which provide an abundant water supply well into early summer. Under these conditions, bleached soil horizons have developed with iron pan formation, resulting in poor soil drainage, strongly correlated with quite different plant communities.     

大鼠脑胆碱能系统对血量扩张引起利尿与尿钠排泄的作用

本工作在清醒大鼠侧脑室注射胆碱能药物,观察脑胆碱能系统对血量扩张引起利尿与尿钠排泄的作用。侧脑室注射人工脑脊液后进行血量扩张引起尿流量、排钠量和排钾量显著增加(P<0.01)。侧脑室注射胆碱能 M 受体阻断剂阿托品后,血量扩张引起尿流量、排钠量和排钾量增加的效应比注射人工脑脊液组的均显著减弱(P<0.01);而侧脑室注射胆碱能 N 受体阻断剂六烃季胺后,血量扩张引起尿流量、排钠量和排钾量增加的效应与注射人工脑脊液组的相比无显著差异(P>0.05)。侧脑室注射人工脑脊液或阿托品大鼠的肾小球滤过率(GFR)与肾血浆流量(RPF)在血量扩张后均无显著变化(P>0.05)。上述结果表明:大鼠脑胆碱能M 受体参与血量扩张引起利尿与尿钠排泄反应的调节。脑 M 受体的这种作用不是通过改变GFR 和 RPF,而可能是通过未明神经液递机制直接影响肾小管对水钠的重吸收。     

Stimulation of acid invertase activity by indol-3yl-acetic acid in tissues undergoing cell expansion

The soluble acid invertase activity of young, excised P. vulgaris internodal segments fell when they were incubated in water, and their elongation ceased within 6–7 h. IAA (10 M) promoted segment elongation and stimulated an increase in the specific activity of acid invertase to a level greater than that originally present. The rate of segment elongation in the presence of IAA was closely and positively correlated with the specific activity of the enzyme. Optimum concentration of IAA for both elongation and stimulation of invertase activity was 10 M. Concurrent protein synthesis was necessary for these responses to IAA. Segments cut from mature, fully-elongated internodes did not responsd to IAA.Inclusion of Ca²⁺, vanadate or mannitol in the incubation medium abolished IAA-induced segment elongation but did not inhibit the stimulation of acid invertase activity by IAA. Auxin-induced elongation and acid invertase activity were both substantially increased in the presence of up to 25 mM D-glucose or up to 50 mM sucrose. Inclusion of either sugar in the medium considerably increased tissue hexose concentrations. Under some circumstances cell growth and invertase synthesis may compete for available hexose substrate.It is concluded that IAA-induced promotion of acid invertase in P. vulgaris internodal segments is not simply an indirect consequence of removal of end-product (hexose) during IAA-induced cell growth and that a more direct action of IAA on enzyme turnover is involved.     

Some characteristics of monolayers of 1-palmitoyl-2-oleoyl-phosphatidylglycerol with and without dipalmitoylphosphatidylcholine during dynamic compression and expansion

Some properties of monolayers of $\text{1-}\text{palmitoyl}\text{-2-}\text{oleoyl}\text{-sn-}\text{glycero}\text{-3-}\text{phospho}\text{-rac-}\text{glycerol}$ (POPG) alone or of POPG in mixtures with $\text{1,2-}\text{dipalmitoyl}\text{-sn-}\text{glycero}\text{-3-}\text{phosphocholine}$ (DPPC) have been measured near 35°C during dynamic compression and expansion at 3.6 cm²·s^?1. (2) The mean values of minimum surface tension (corresponding to maximum surface pressure) which could be obtained with pure POPG monolayers at high compression ranged from 15 to 18 mN·m^?1 in the presence of Na⁺, Ca²⁺ or low pH (2.0) in the subphase. (3) The presence of Ca²⁺ or low pH in the subphase increased the collapse plateau ratios obtained on cyclic compression. This might represent enhanced respreading into the monolayer of pure POPG from a collapsed form during reexpansion of the surface. (4) Monolayers containing 10% or 30% POPG and 90% or 70% DPPC could be compressed to surface tensions approaching zero. (5) In such mixed monolayers, 10% or 30% POPG did not appear to enhance respreading, as measured by collapse plateau ratios, in the presence of Na⁺ or Ca²⁺ in the subphase.     

EFFECTS ON FITNESS COMPONENTS OF P-ELEMENT INSERTS IN DROSOPHILA MELANOGASTER: ANALYSIS OF TRADE-OFFS

We analyzed the trade-offs between fitness components detected in four experiments in which traits were manipulated by inserting small (control) and large (treatment) P-elements into the Drosophila melanogaster genome. Treatment effects and the interactions of treatment with temperature, experiment, and line were caused by the greater length and different positions of the treatment insert. In inbred flies, the treatment decreased early and total fecundity. Whether it increased the lifespan of mated females depended upon adult density. Analysis of line-by-treatment-by-temperature interactions revealed hidden trade-offs that would have been missed by other methods. They included a significant trade-off between lifespan and early fecundity. At 25°C high early fecundity was associated with decreased reproductive rates and increased mortality rates 10–15 days later and persisting throughout life, but not at 29.5°C. Correlations with Gompertz coefficients suggested that flies that were heavier at eclosion also aged more slowly and that flies that aged more slowly had higher fecundity late in life at 25°C. The results support the view that lifespan trades off with fecundity and that late fecundity trades off with rate of aging in fruitflies. Genetic engineering is an independent method for the analysis of trade-offs that complements selection experiments.     

Potential for host range expansion in Ceratitis capitata flies: impact of proximity of adult food to egg-laying sites

Abstract.

• 1 In field cage and field tests, female Mediterranean fruit flies, Ceratitis capitata (Wiedemann), in trees alighted in significantly greater numbers upon sticky-coated (non-odour-emitting) kumquats, Fortunella japonica, that were in the vicinity of odorous natural proteinaceous food (bird faeces) or synthetic food odour than on similar kumquats distant from bird faeces or synthetic food odour.
• 2 In field cage tests, oviposition in non-sticky kumquats nearby bird faeces was significantly greater than in non-sticky kumquats distant from bird faeces.
• 3 In field tests, medflies laid significantly more eggs in host kumquat and non-host hawthorn, Crataegus mollis, fruit adjacent to bird faeces and synthetic food odour than in fruit of these types distant from food-type stimuli.
• 4 These findings suggest that odour of natural food of medflies could lure flies to plants whose fruit emit little or no attractive odour and are not permanent hosts but which are nonetheless susceptible to egg-laying and larval development, resulting in temporary expansion of host range.

     

Heuristic optimization of the general life history problem: A novel approach

Summary The general life history problem concerns the optimal allocation of resources to growth, survival and reproduction. We analysed this problem for a perennial model organism that decides once each year to switch from growth to reproduction. As a fitness measure we used the Malthusian parameterr, which we calculated from the Euler-Lotka equation. Trade-offs were incorporated by assuming that fecundity is size dependent, so that increased fecundity could only be gained by devoting more time to growth and less time to reproduction. To calculate numerically the optimalr for different growth dynamics and mortality regimes, we used a simplified version of the simulated annealing method. The major differences among optimal life histories resulted from different accumulation patterns of intrinsic mortalities resulting from reproductive costs. If these mortalities were accumulated throughout life, i.e. if they were senescent, a bangbang strategy was optimal, in which there was a single switch from growth to reproduction: after the age at maturity all resources were allocated to reproduction. If reproductive costs did not carry over from year to year, i.e. if they were not senescent, the optimal resource allocation resulted in a graded switch strategy and growth became indeterminate. Our numerical approach brings two major advantages for solving optimization problems in life history theory. First, its implementation is very simple, even for complex models that are analytically intractable. Such intractability emerged in our model when we introduced reproductive costs representing an intrinsic mortality. Second, it is not a backward algorithm. This means that lifespan does not have to be fixed at the begining of the computation. Instead, lifespan itself is a trait that can evolve. We suggest that heuristic algorithms are good tools for solving complex optimality problems in life history theory, in particular questions concerning the evolution of lifespan and senescence.