MITOCHONDRIAL GENOTYPES HAVE NO DETECTABLE EFFECTS ON MERISTIC TRAITS IN CUTTHROAT TROUT HYBRID SWARMS

Efforts to detect effects of cytoplasmic genes are confounded by the problem of partitioning nuclear and cytoplasmic effects. In this study we test for effects of mtDNA haplotype on development in hybrid populations of cutthroat trout (Oncorhynchus clarki) with randomly associated nuclear and mtDNA genotypes. We have previously described several intraspecific hybrid swarms formed by interbreeding of westslope cutthroat trout (O. c. lewisi) and Yellowstone cutthroat trout (O. c. bouvieri). Genetic distance between these subspecies is high (Nei's D = 0.30; mtDNA P = 0.02), and diagnostic alleles at multiple nuclear loci and two distinct mtDNA haplotypes are present in the hybrids. Historical associations between alleles at nuclear loci and between cytotypes and nuclear alleles have largely decayed. We test for differences in meristic characters between fish with alternate mtDNA haplotypes. Counts and fluctuating bilateral asymmetry for these characters have been previously shown to be sensitive indicators of genetic differences that affect development. No differences were found between mtDNA types in meristic counts or fluctuating asymmetry. Therefore, the alternate mtDNA haplotypes had no detectable effect on development as measured by meristic counts in these hybrid populations. However, diagnostic alleles at one nuclear allozyme locus (CK-CI) were associated with several fin ray counts.     

ON THE LOW HERITABILITY OF LIFE-HISTORY TRAITS

Life-history traits such as longevity and fecundity often show low heritability. This is usually interpreted in terms of Fisher's fundamental theorem to mean that populations are near evolutionary equilibrium and genetic variance in total fitness is low. We develop the causal relationship between metric traits and life-history traits to show that a life-history trait is expected to have a low heritability whether or not the population is at equilibrium. This is because it is subject to all the environmental variation in the metric traits that affect it plus additional environmental variation. There is no simple prediction regarding levels of additive genetic variance in life-history traits, which may be high at equilibrium. Several other patterns in the inheritance of life-history traits are readily predicted from the causal model. These include the strength of genetic correlations between life-history traits, levels of nonadditive genetic variance, and the inevitability of genotype-environment interaction.     

Physiological and Molecular Basis of Susceptibility and Tolerance of Rice Plants to Complete Submergence

Rice plants are much damaged by several days of total submergence.The effect can be a serious problem for rice farmers in therainfed lowlands of Asia, and runs contrary to a widespreadbelief amongst plant biologists that rice is highly tolerantof submergence. This article assesses the characteristics ofthe underwater environment that may damage rice plants, examinesvarious physiological mechanisms of injury, and reviews recentprogress achieved using linkage mapping to locate quantitativetraits loci (QTL) for tolerance inherited from a submergence-tolerantcultivar FR13A. Progress towards identifying the gene(s) involvedthrough physical mapping of a dominant tolerance locus on chromosome9 is also summarized. Available physiological evidence pointsaway from responses to oxygen shortage as being inextricablyinvolved in submergence injury. An imbalance between productionand consumption of assimilates is seen as being especially harmful,and is exacerbated by strongly accelerated leaf extension andleaf senescence that are ethylene-mediated and largely absentfrom FR13A and related cultivars. DNA markers for a major QTLfor tolerance are shown to be potentially useful in breedingprogrammes designed to improve submergence tolerance.     

Trophic links,nutrient fluxes,and natural history in the Allium ursinum food web,with particular reference to life history traits of two hoverfly herbivores (Diptera: Syrphidae)

The food web centering on Allium ursinum (Liliaceae) in a beech forest (Germany) is described, and temporal variation of active trophic links is related to species' life cycles. The most important insect herbivores are Cheilosia fasciata (a larval leaf miner) and Portevinia maculata (a larva bulb miner) (Diptera: Syrphidae). Energy, carbon and nitrogen flow in the food chain (Allium-Cheilosia-Phygadeuon ursini) are investigated and analysed with respect to differences in resource allocation by the leaf miner and its hymenoptereous parasitoid. In C. fasciata nitrogen is likely to be the limiting resource, while growth in Phygadeuon ursini appears energy-limited. Larval feeding habits of C. fasciata and Portevinia maculata determined the timing of the species' life cycles and, as a consequence, appeared to preclude the existence of a pupal parasitoid in Portevinia maculata. Further details of life history traits are demonstrated and discussed.     

Phalaenopsis bellina (Rchb.f.) Christenson,a segregate from P. violacea Witte (Orchidaceae: Aeridinae)

A reevaluation of floral and vegetative morphology together with data from analysis of floral fragrance and flavonoid co-pigment chemistry suggest that specific status is warranted for the two kinds ofPhalaenopsis violacea Witte known informally as the “Bornean type” and the “Malayan type.”Phalaenopsis violacea var.bellina Rchb.f. is elevated to specific rank, providing a name for the “Bornean type” plants.     

Floral development of Bougainvillea spectabilis Willd., Boerhaavia diffusa L. and Mirabilis jalapa L. (Nyctaginaceae)

Three morphological problems were investigated in three species of the Nyctaginaceae: epiphylly, phyllotaxis and placentation. Epiphylly, which occurs in Bougainvillea spectabilis , is the result of ontogenetic displacement resulting from the activity of an intercalary meristem at the base of the floral bract and the floral bud. Floral development of Bougainvillea spectabilis was compared with that of Boerhaavia diffusa and Mirabilis jalapa . Considerable variation occurs with regard to the number and arrangement of stamens. Five stamens are initiated simultaneously, alternate to the petals, in Mirabilis . In Bougainvillea , eight stamens arise sequentially at divergence angles suggestive of a 3/8 spiral. No developmental evidence was found to support the derivation of the eight stamens from a two whorled pentamerous androecium. Boerhaavia normally has only two stamens which most frequently are initiated toward opposite sides of the floral apex, but may also be formed in a 2/5 to 3/8 divergence. In some flowers only one or three stamens are formed. The gynoecium is formed in the same way in all three species: growth occurs in a crescent-shaped zone at the periphery of the floral apex thus producing the gynoecial wall. The single ovule, which is basal in the mature gynoecium, is formed from the gradual upgrowth and transformation of the floral apex and is developmentally terminal. Even the two-layered tunica is maintained as the floral apex is transformed into the ovule primordium. If 'carpel' is defined traditionally as a folded megasporophyll which bears and encloses ovule(s) then carpels are not present in the gynoecia of the three species studied. If 'carpel' is re-defined as an appendage which encloses ovule(s), then the gynoecia of the Nyctaginaceae are carpellate. However, the ovules remain cauline regardless of which definition is adopted.     

小麦根系特征对干旱胁迫的响应

干旱胁迫时, 小麦(Triticum aestivum)根系率先产生应激响应, 同时向地上部发出信号, 诱导地上部发生生理反应, 从而提高植株抗旱能力。根系构型包括平面几何性状和立体几何结构(即拓扑构型), 具有遗传稳定性和可塑性。干旱胁迫影响根系理化特性, 如根源化学信号、根系细胞酶类和根系渗透作用的响应。根系通过调整其解剖学结构和水分吸收动力等来适应干旱胁迫。该文从根系构型、理化特性和解剖学结构3个方面, 系统阐述了小麦根系特征对干旱胁迫的响应, 并探讨了其与干旱胁迫的关系和当前研究中存在的问题, 以期为相关研究提供参考。     

子莲新品种‘武植子莲1号’和‘武植子莲2号’产量与营养品质分析

对子莲（Nelumbo nucifera Gaertn.）新品种‘武植子莲1号’和‘武植子莲2号’与其他12个主栽子莲品种的莲子产量和品质性状进行分析,并通过隶属函数分析法对他们的营养品质性状进行综合评价。结果显示：不同子莲品种的产量和营养品质性状差异显著,同一品种在不同发育时期莲子的可溶性糖和淀粉含量等营养指标差异较大;鲜莲子的可溶性糖含量显著高于成熟莲子,而蛋白质和淀粉含量显著低于成熟莲子。与12个主栽子莲品种相比,‘武植子莲1号’在产量上较为突出,成熟莲子的淀粉含量达52.15%,是生产天然淀粉的优良品种;‘武植子莲2号’鲜莲子的直链淀粉和支链淀粉含量低,可溶性糖含量达23.43%,适合鲜食。隶属函数分析结果表明,‘武植子莲1号’和‘武植子莲2号’的综合营养品质较好,具有很高的应用价值。     

Reproductive ecology of dioecious Siparuna (Monimiaceae) in Ecuador–a case of gall midge pollination

The reproductive ecology of the dioecious genus Siparuna , belonging to the primitive family Monimiaceae, was investigated in Ecuador. Thirteen species were studied, and species growing at high altitudes (above 500 m) were compared with species growing at lower altitudes. The genus has specialized flowers pollinated by Cecidomyiidae (Asynapta sp. and other genera) that lay eggs chiefly in male flowers since these are more easily accessible than female flowers due to their morphology. Several traits ensure that pollen transfer is accomplished: 1. long flowering of individuals and single flowers; 2. specific floral morphology (unisexuality, landing platform, restricted pore) allowing the flowers to be visited by Cecidomyiidae seeking egg-laying sites, and 3. a low number of ovules that have to be pollinated in each flower. The low number of ovules per flower results in a high pollen-ovule (P/O) ratio even though pollen production in male flowers is only moderate.
High altitude species had larger flowers, higher pollen-ovule ratios, fewer ovules per female flower, and longer periods of anthesis. Gender differences were seen in the longer functionality of female flowers; the larger numbers of male flowers produced; and the average diameter at breast height (DBH) biased for one of the two sexes depending on the species investigated, with no clear trend in the size distributions of individuals of both sexes. Sex ratios departed significantly from unity both to male and female bias but usually were in favour of males. There were no general differences in the ratio of functional male to female flowers at the time of observation nor in the sizes of male and female flowers. The evolution of unisexual flowers in Siparuna can be explained as a result of the differential predation by larvae: unimportant in male flowers, destructive if occurring in female flowers.