Genetic specificity of nitrogen nutrition in leguminous plants

Summary Mineral nitrogen did not increase grain yield and seed protein levels ofVicia faba L. andLupinus luteus L. in field trials and pot experiments. Fixed N₂ was substituted by mineral nitrogen in these cases because of inhibition of N₂ fixation by mineral nitrogen. Contrary to these results mineral nitrogen increased grain yields and seed protein amounts ofLupinus albus L.,Pisum sativum L., andGlycine max. (L.) Merr. The nitrogen effect was caused at an early stage by saving energy due to inhibition of N₂ fixation (measurement of gas exchange by means of IRGA). In case of the N application after flowering grain, yields and seed protein levels increased because the mineral N was an additional nitrogen source for plants. At this stage the plants had ceased fixing atmospheric nitrogen. The high sink activity of growing fruits induced a lack of assimilates in nodules (determined by means of¹⁴CO₂ application). The N effect was therefore the consequence of the lower assimilate pool for supplying root nodules in these plants in comparison withVicia faba L. andLupinus luteus L. Hence it follows that response to mineral nitrogen can be a criterion for discovering more effective Rhizobium-host combinations.     

Structural organization of the normal and anoxic heart of Scyllium stellare

Summary The general and ultrastructural organization of the heart of the elasmobranch, Scyllium stellare, was studied in normal and in anoxic animals. The rich coronary supply was revealed three-dimensionally by the use of corrosion casts, showing a thebesian system of coronary arterioles and capillaries in the thin, outer compact layer as well as in the predominant, inner spongy layer of trabeculae.Only the sinus venosus received a neuronal input of large bundles of granule-containing axons terminating at fenestrated regions of the endocardium and suggesting a neurohormonal function.A simple, tubular sarcoplasmic reticulum with flattened junctional cisternae was present in myocardial cells of 1–5 m diameter, which contained one or two bundles of myofibrils. The latter were closely apposed to the inner aspect of the plasmalemma. Mitochondria were located centrally in the cells, which were joined by unfolded desmosomes involving Z-band material.Long periods of anoxia were tolerated without loss of heart function, but at the expense of cytoplasmic glycogen. Lipid granules were abundant in all layers and chambers, notably in animals prepared in the summer. The lipid granules displayed a marked increase in electron density when the heart was incubated in a buffered oxalate solution prior to fixation. A glycogen-sparing effect of the lipids during anoxia was observed.     

Chromosomal evolution withinPiperaceae

Chromosome numbers for 26 different species of the generaPiper, Peperomia andPothomorphe (Piperaceae) are reported. The basic chromosome numbers are 2n = 26, x = 13 (Piper, Pothomorphe) and 2n = 22, x = 11 (Peperomia), polyploid series are characteristic forPiper andPeperomia. Piper has the smallest chromosomes and prochromosomal interphase nuclei,Peperomia the largest ones and mostly reticulate to euchromatic nuclei.Pothomorphe is intermediate in both characters. The karyomorphological differences betweenPothomorphe andPiper underline their generic separation. Interspecific size variation of chromosomes occurs inPiper andPeperomia. Infraspecific polyploidy was observed inPiper betle. C-banding reveals different patterns of heterochromatin (hc) distribution between the genera investigated. The genome evolution is discussed.     

Influences of root distribution and growth on predicted water uptake and interspecific competition

Summary Root distribution and growth measured in the field were incorporated into a water uptake model for the CAM succulent Agave deserti and its nurse plant Hilaria rigida, a common desert bunchgrass. Agave deserti responds to the infrequent rainfalls of the Sonoran Desert by extending its existing established roots and by producing new roots. Most of such root growth was completed within one month after soil rewetting, total root length of A. deserti increasing by 84% for a seedling and by 58% for a mediumsized plant in the summer. Root growth in the winter with its lower soil temperatures was approximately half as much as in the summer. For a 15-year period, predicted annual root growth of A. deserti varied more than 18-fold because of annual variations in rainfall amount and pattern as well as seasonal variation in soil temperature. Predicted annual water uptake varied 47-fold over the same period. The nurse plant, which is crucial for establishment of A. deserti seedlings, reduced seedling water uptake by 38% during an average rainfall year. Lowering the location of the root system of a medium-sized A. deserti by 0.24 m reduced its simulated annual water uptake by about 25%, reflecting the importance of shallow roots for this desert succulent. Lowering the root system of a medium-sized H. rigida by 0.28 m increased the simulated annual water uptake of an associated A. deserti seedling by 17%, further indicating the influence of root overlap on competition for water.     

Insect capture and growth of the insectivorous Drosera rotundifolia L.

Summary Rates of insect capture increased with leaf area in the insectivorous plant Drosera rotundifolia, and growth of new leaves was related to insect capture. However, increased leaf growth was counterbalanced by leaf abscission which was in turn related to insect capture and leaf growth. Leaf loss equaled leaf growth in plants having natural rate of insect capture. A large proportion of the nitrogen gain from prey was stored in the hypocotyl; it was estimated from feeding experiments that about 24% to 30% of the nitrogen stored in the hypocotyl after winter originated from insect capture in the previous season. The effect of insect capture is discussed in relation to the life cycle of Drosera.     

Growth and development of Brassica genotypes differing in endogenous gibberellin content. II. Gibberellin content, growth analyses and cell size

Three rapid cycling Brassica rapa genotypes were grown in greenhouse conditions to investigate the possible relationships between endogenous gibberellin (GA) content and shoot growth. Endogenous GA₁ GA₃ and GA₂₀ were extracted from stem samples harvested at 3 weekly intervals and analyzed by gas chromatography-mass spectrometry with selected ion monitoring, using [²H₂]-GA₁ and [²H₂]-GA₂₀ as quantitative internal standards. During the first 2 weeks, GA levels of the dwarf, rosette ( ros ), averaged 36% of levels in normal plants (on a per stem basis). Levels in the tall mutant, elongated internode (ein) , were consistently higher, averaging 305% of levels in normal plants.
Differences in shoot height across the genotypes resulted from varying internode length which resulted from epidermal cell length and number being increased in ein and decreased in ros relative to the normal genotype. The exogenous application of GA₃ to normal plants increased cell length while the application of paclobutrazol (PP333), a triazole plant growth retardant, reduced cell size. Thus, exogenous GA manipulations mimicked the influence of the mutant genes ros and ein. The dwarf, ros , had reduced shoot dry weights and relative growth rates compared to the other genotypes. Total dry weights were similar in ein and the normal genotype but stem weights were increased in ein , compensating for decreased leaf weights. Thus, the gibberellin-deficiency of ros resulted in generally reduced shoot growth. The overproduction of endogenous GA by ein did not result in enhanced shoot growth but rather a specific enhancement of internode elongation and stem growth at the expense of leaf size.     

湖北第二批国家珍稀濒危保护植物

本文经调查记述了湖北第二批国家重点保护植物16种,分属12科16属,可为我省珍稀濒危植物资源的保护及合理利用提供参考。     

浙江珍稀濒危保护植物的地理分布及其区系特征

本文分析了浙江珍稀濒危保护植物56种的地理分布和51属的分布区类型及其区系特征,其结果如下: 1.本区存在较多的我国特有属,单型属、少型属的事实,说明浙江省的珍稀濒危植物区系的古老性和相对原始性。2.根据51属的分布区类型的分析,其属具有明显的温带性质,而56种的地理分布则以亚热带区系成分为主,它们与华中亚热带区系植物关系密切。