Fruit set in a deceptive orchid: The effect of flowering phenology,display size,and local floral abundance

We investigated the effect of flowering time, display size, and local floral density on fruit set in Tolumnia variegata, a pollination-limited orchid that offers no reward to its pollinator(s). During 1990, natural variation in flowering time, display size, and fruit set were monitored in 508 plants at one locality in Puerto Rico. The following season, orchid floral abundance per host tree (Randia aculeata) was manipulated to investigate its effect on fruit set. Four floral abundance treatments were established (700, 500, 300, and 100), each replicated four times. Flowering time was the most important trait affecting fruit set. The proportion of plants setting at least one fruit was significantly high early and late in the season, but low during the flowering peak. Thus, strong disruptive selection differential on flowering phenology was found. Display size had little effect on fruit set. A weak, but significant disruptive selection differential on display size was found. Orchid floral abundance per host tree had a significant effect on fruit set. Early in the season, T. variegata flowers with intermediate number of conspecific flowers exhibited a greater probability of setting fruit than those in host trees with fewer or more flowers. Our results show that flowering phenology may be evolutionarily unstable, possibly a consequence of the deception pollination system. Furthermore, a deception strategy would be relatively unsuccessful in populations where plants are found in either very dense or sparse patches.     

The current status of European wetland inventories and classifications

The status of wetland inventory and classification is considered for 44 European countries, as well as for the continent as a whole. Data and information were obtained from questionnaires compiled by the International Waterfowl and Wetland Research Bureau, the MedWet sub-project on inventory and monitoring, and the Ramsar Bureau. Nine European countries have national wetland inventories, and 32 have inventories of sites of international importance listed under the Ramsar Convention. There has been a trend in producing regional or continental inventories for wetlands that are important as waterfowl habitat. There is an urgent need to produce wetland inventories for all European countries. The Ramsar database takes into consideration hydrological and economic wetland values, as well as ecological ones. The Ramsar classification lists a total of 35 wetland types, and is sufficiently flexible that it could be used for classifying European wetlands at the national scale.     

杨桃果实采后生理研究(综述)

概述了国内外对杨桃果实采后主要营养成分的分析、呼吸、乙烯释放、主要生理病害,并介绍了不同贮藏条件或处理对杨桃果实采后贮藏性影响的研究概况。     

Dominance, competition, and energetic reserves in the European starling, Sturnus vulgaris

We investigated the relationships between social dominance,competition for food, and strategies of body mass and fat regulationin the European starling (Sturnus vulgaris). In birds housedin groups of three, subdominant birds stored more fat than dominants.A removal experiment established a causal link between socialdominance and fat reserves; in groups that had the dominantindividual removed, the remaining birds reduced body mass andfat, relative to control groups that had the subordinate removed.In a second experiment, we investigated the influences of degreeof competition for food and dominance on body mass and fat reserves.Birds under high competition increased fat reserves and tendedto have higher body mass than birds under low competition. Theincrease in fat reserves was higher in the subdominants thanin the dominants. These results are consistent with hypothesesconcerning dominance-dependent access to food; subdominant birds,or birds under increased competition, may store more fat asan insurance against periods when food cannot be obtained. However,relations between dominance, body mass, and fat reserves mayalso arise through other proximate factors relating to dominance-dependentcosts and benefits of fat storage, such as predation risk andenergetic expenditure.     

Search for rhythmicity during hibernation in the European hamster

Temporal patterns of hibernation were studied by continuous monitoring of body temperature by radiotelemetry over 6 months in European hamsters, Cricetus cricetus, at constant temperature and photoperiod. Entrances into hibernation occurred mostly at the end of the night (0000–0800 hours), while arousals were randomly distributed between day and night. This is at variance with a control of bout duration by a clock with a period of 24 h. Consequently, the timing of entrances implies a phase-resetting of the circadian clock on each arousal. Persistence of circadian rhythmicity with a period different from 24 h during deep hibernation was investigated examining whether the durations of torpor bouts were integer multiples of a constant period. A non-parametric version of the classical contingency test of periodicity was developed for this purpose. Periods ranging from 21 to 29 h were tested. Nine animals out of ten showed at least one significant period in this range (P<0.01), either below 24 h (21.8±0.5 h, n=4) or above (27.3±0.5 h, n=7). However, we have found a theoretical model of bout durations for which the contingency test of periodicity sometimes gives false significant results. This indicates that the power of the test is weak. With this reservation our results suggest that a circadian oscillator controls the duration of a bout of hibernation, which would occur after an integer, but variable and possibly temperature-dependent number of cycles.Abbreviations _b a contingency test (see Appendix) - SCN suprachiasmatic nuclei - period - T _b body temperature     

Strong synergistic effects of gibberellins with the synthetic cytokinin N-(2-chloro-4-pyridyl)-N-phenylurea on parthenocarpic fruit set and some other fruit characteristics of apple

The induction of parthenocarpic fruit set was investigated using the apple cvs. Golden Delicious and Jonagold. The gibberellins GA₃, GA₄, GA₅ and GA₇ and the synthetic phenylurea-type cytokinin CPPU (N-(2-chloro-4-pyridyl)-N-phenylurea), were applied alone and in combination to unpollinated flowers at the end of petal fall. Gibberellins induced only a marginal final set of parthenocarpic fruits. CPPU sprays were more effective, particularly in the first year. When applied in combination, CPPU and gibberellins had a positive synergistic effect on parthenocarpic fruit set and fruit size, but a negative effect on flower induction the next year. After CPPU + GA sprays, percent fruit set was similar, or greater, compared to natural pollinated trees. The parthenocarpic fruits induced by CPPU + GA had an increased length to diameter ratio. CPPU stimulated, and GA₄ and GA₇ reduced, the russeting of the parthenocarpic fruits. The internal quality of the fruits was hardly affected, but Ca-deficiency symptoms occurred more frequently in parthenocarpic fruits.     

Morphometric and DNA investigations into European water frogs (Rana kl. esculenta Synklepton (Anura, Ranidae)) from different population systems

The population specific variability of diploid and triploid R. kl. esculenta individuals was investigated by means of morphometric methods (canonical discriminant analysis, UPGMA cluster analysis) and DNA fingerprinting. As a result of the morphometric investigations, as well as of the DNA investigations, a clear separation of single populations was possible. However, no correlations between the morphometry and different population systems could be recognized. Clear morphometric differences could be seen between diploid ♀♀ and ♂♂ and triploid ♀♀ on the one hand, and triploid ♂♂ on the other. While the diploid ♀♀ and ♂♂ and the triploid ♀♀ were located in the intermediate area between the parental species R. lessonae and R. ridibunda according to their morphometric parameters, the triploid ♂♂ showed a great overlap with R. lessonae. Up to now, this phenomenon has not been explained. The first results of the DNA investigations provided further hints at the high inter-individual and population-specific variability of R. kl. esculenta. R. kl. esculenta individuals of the R. lessonae/esculenta population Toter See could be distinguished from conspecific individuals of the R. ridibunda/esculenta-♀♀ population Alte Oder according to their fingerprint patterns. Moreover, in the R. lessonae / esculenta population, the fingerprints or the diploid R. kl. esculenta-♀♀ and the investigated R. lessonae-♀ were very similar. Furthermore, in this population, many R. kl. esculenta genotypes resemble R. lessonae in their morphometric features. This finding suggests the occurrence of recombination in R. kl. esculenta. In general, every population seems to have its own genetic background. A classification of water-frog populations according to population systems is only possible under certain conditions.     

离体条件下诱导番茄果实状结构的再生

以番茄（Ｌｙｃｏｐｅｒｓｉｃｏｎ ｅｓｃｕｌｅｎｔｕｍ Ｍｉｌｌ．）雌蕊和幼果的组织作外植体可以诱导果实状结构的再生。这种果实状结构在离体条件下能培养成熟,成熟时具红色。解剖观察表明：果实状结构由果肉和包围在外面的果皮组成,无种子和胎座。外源激素和外植体年龄的试验揭示：１．以雌蕊组织作外植体时,仅附加外源细胞分裂素就可以诱导果实状结构的再生,外源生长素似乎不是必需的,最高的诱导频率（５０．０％ ）出现在仅附加玉米素０．５ ｍ ｇ／Ｌ的组合。２．从直径４—１２ ｍ ｍ 的幼果上分离的外植体在附加外源激素的培养基上均可诱导果实状结构的再生,但只有从直径８ ｍ ｍ 的果实分离的组织块作外植体并将它们培养在６－ＢＡＰ ２ ｍ ｇ／Ｌ,ＮＡＡ０．１ ｍ ｇ／Ｌ的培养基上时,果实状结构的诱导频率最高（６２．５％ ）。为了探讨在果实状结构再生中表现出来的细胞全能性的表达,提出了植物细胞全能性的部分表达（Ｐａｒｔｉａｌｅｘｐｒｅｓｓｉｏｎ ｏｆｐｌａｎｔ ｃｅｌｌｔｏｔｉｐｏｔｅｎｃｙ）的概念并进行了讨论。     

Use of lysophosphatidylethanolamine, a natural lipid, to retard tomato leaf and fruit senescence

We studied the influence of lysophosphatidylethanolamine (LPE) on the pattern and rate of ethylene production and respiration of tomato ( Lycopersicon esculentum cv. H7155) leaflets and fruit. Leaflets that had been senescing on the plant showed a climacteric-like rise in ethylene production but not in respiration rate which decreased continuously with leaf age. Detached leaflets had a climacteric-like pattern in respiration whether they were incubated in complete darkness or in light. Detached leaflets incubated in the dark had higher rates of ethylene production and CO₂ evolution than did light-incubated leaves. There was no change in the pattern of ethylene production or CO₂ evolution as a result of LPE treatment. However, LPE-treated attached and detached leaflets had consistently lower rates of CO₂ evolution. The reduction in CO₂ evolution by LPE was most pronounced at the climacteric-like peak of the detached leaves. LPE-treated leaflets had a higher chlorophyll content and fresh weight and lower electrolyte leakage than the control. LPE-treated fruits had lower rates of ethylene and CO₂ production than did the control. LPE-treated fruits also had higher pericarp firmness and lower electrolyte leakage than the control. The results of the present study provide evidence that LPE is able to retard senescence of attached leaves and detached leaves and tomato fruits. Several recent studies suggest that lysolipids can act in a specific manner as metabolic regulators. Our results suggest a specific role of lysolipid LPE in aging and senescence