A late Wenlock flora from Co. Tipperary, Ireland

An assemblage of macroplants preserved as highly coalified compressions which lack anatomy is described from a Wenlock locality in County Tipperary, Ireland. Most of the fertile specimens are assigned to Cooksonia Lang. The taxonomic status of this genus is discussed. Some poorly preserved palynomorphs, including miospores, acritarchs, chitinozoans and a variety of tubes, have been isolated from associated sediments, but the age of the flora is based on graptolites. Sedimentological and palaeontological studies of the region are summarized. They provide little direct evidence for the habitats of the plants which are considered to have been terrestrial. The relevance of this flora to the current debate on the colonization of the land is evaluated and it is concluded that these plants provide the earliest record of erect fertile land plants of possible pteridophyte affinity.     

Volatile constituents of the leaves of Cupressus dupreziana and Cupressus sempervirens

The essential oils of the leaves of Cupressus dupreziana and Cupressus sempervirens were compared. The composition of the hydrocarbon fraction showed a great similarity between the two species.     

Nutrition of winter wheat during the life cycle. I. Yield and accumulation of dry matter and minerals

Mineral uptake by winter wheat (Trilicum aestivum L. cv. Martonvasari 8) was studied throughout the life cycle. Accumulation of macronutrients (i.e. total nitrogen, phosphorus, potassium, sodium, magnesium and calcium) and the water content of roots and shoots of plants grown in complete nutrient solution were higher than those of plants grown in two types of soils. The supply of macronutrients was in some cases limiting for soil-grown plants as revealed by a comparison of available and accumulated amounts of these nutrients. Their supply was abundant, however, for solution-grown plants. This led to a doubling of grain yield for the latter plants with a three fold increase in accumulation of dry matter and a five-fold increase in fresh weight. The efficiency ratios of solution-grown plants to soil-grown plants were approximately 1 for N and Na, 0.5 for Mg and Ca, and 0.3 for P and K.     

Some variations in the composition of suberin from the cork layers of higher plants

The monomeric composition of the suberins from 16 species of higher plants was determined by chromatographic methods following depolymerization of the isolated extractive-free cork layers with sodium methoxide-methanol. 1-Alkanols (mainly C₁₈C₂₈), alkanoic (mainly C₁₆C₃₀), α,ω-alkanedioic (mainly C₁₆C24), ω-hydroxyalkanoic (mainly C₁₆C₂₁), dihydroxyhexadecanoic (mainly 10,16-dihydroxy- and 16-dihydroxyhexadecanoic), monohydroxyepoxyalkanoic (9,10-epoxy-18-hydroxyoctadecanoic), trihydroxyalkanoic (9,10, 18-trihydroxyoctadecanoic), epoxyalkanedioic (9,10-epoxyoctadecane-1,18-dioic) and dihydroxyalkanedioic (9,10-dihydroxyoctadecane-1 18-dioic) acids were detected in all species. The suberins differed from one another mainly in the relative proportions of these monomer classes and in the homologue content of their 1-alkanol, alkanoic, α,ω-alkanedioic and ω-hydroxyalkanoic acid fractions. C₁₈ epoxy and vic-diol monomers were major components (32–59%) of half of the suberins examined (Quercus robur, Q. ilex, Q. suber, Fagus sylvatica, Castanea sativa, Betula pendula, Acer griseum, Fraxinus excelsior) where as ω-hydroxyalkanoic and α,ω-alkanedioic acids predominated in those that contained smaller quantities of such polar C₁₈ monomers (Acer pseudoplatanus, Ribes nigrum, Euonymus alatus, Populus tremula, Solanum tuberosum, Sambucus nigra, Laburnum anagyroides, Cupressus leylandii). All species, however, contained substantial amounts (14–55 %) of ω-hydroxyalkanoic acids, the most common homologues being 18:1 (9) and 22: 0. The dominant α,ω-alkanedioic acid homologues were 16: 0 and 18: 1 (9) whereas 22: 0, 24: 0 and 26: 0, and 20: 0, 22: 0 and 24: 0 were usually the principal homologues in the 1-alkanol and alkanoic acid fractions, respectively. The most diagnostic feature of the suberins examined was the presence of monomers greater than C₁₈ in chain length; most of the C₁₆ and C₁₈ monomers identified in the suberins also occur in plant cutins emphasizing the close chemical similarity between the two anatomical groups of lipid biopolymer.     

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.     

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.