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The response of epicuticular wax of Scots pine (Pinus sylvestris L.) needles to dry- and wet- deposited sulphur and heavy metals was investigated at six sites located 10-110 km from the Monchegorsk Cu-Ni smelter on the Kola Peninsula, North-West Russia, and in a long-term irrigation experiment where pines were exposed over four growing seasons (1991-1994) to either acid rain treatment at pH 3.1 (H2SO4), metal treatment at pH 5.7 (Cu and Ni) or a combination of these at pH 3.1. Needle wettability exhibited a closer relationship with epistomatal wax tube distribution (WTD) than with chemical composition of epicuticular wax. Water droplet contact angles (DCA) decreased towards the smelter, and significant differences due to site were noted for 26-month-old and 38-month-old needles. Significant differences due to site were determined for secondary alcohols, dehydroabietic acid and hydroxy fatty acids, the proportions of which ranged from 22.5 to 48.9%, 6.2 to 22.4 % and 0.6 to 2.6% respectively, depending on site and needle age class. The proportion of dehydroabietic acid increased towards the smelter, but no gradient was observed in the proportion of secondary alcohols or hydroxy fatty acids. No major effect of experimentally applied pollutants on the chemical composition or structure of the epicuticular wax was observed. The effect of treatment on DCA was significant in 1993 and 1994 due to a 6.5-13.2 degree greater wettability of the 37-49-month-old acid-treated needles relative to the irrigated or dry controls. Sulphuric acid at pH 3.1 did not increase needle wettability when combined with copper and nickel sulphate in similar concentrations. These data indicate that S deposition, especially H2SO4, plays a more important role in needle surface deterioration than Cu and Ni. Pollutant-induced changes in epicuticular wax structure and needle wettability mimic natural wax ageing, but at an accelerated rate. Changes in wax chemical composition might also be caused by pollutant-induced metabolic changes in elongating needles. [ABSTRACT FROM AUTHOR]

Three groups of species (21 herbaceous monocotyledons, 22 herbaceous dicotyledons and 16 woody dicotyledons), including representatives of a wide range of natural habitats and life forms in inland Britain, were grown in the seedling phase in a resource-rich controlled environment and assessed over a 14-day period (21 d in the case of woody species). Mean values of relative growth rate (RGR), unit leaf rate (ULR), leaf area ratio (LAR), leaf weight fraction (LWF), specific leaf area (SLA), and the root-shoot allometric coefficient were derived. In herbaceous species, the grand mean RGR was 0.20 d-1, comparable to values previously recorded. For woody species, the mean was 0.09 d-1. An existing assumption linking high RGR to high allocation to photosynthetic biomass was upheld by comparisons made between groups. Within groups, however, no pattern of this kind could be demonstrated. When potosynthetically active radiation was increased from 125 to 250 μmol m-2 s-1, ULR was increased almost pro rata. The parallel response in RGR was only slight, being offset by considerable reductions in LAR. The apparent mean quantum yield for photosynthesis in herbaceous species (whole-plant d. wt basis) was 0.60 g mol-1. There was no significant dependence of RGR on ULR in any of the three groups of species, although he absolute magnitude of ULR declined in the order: herbaceous monocotyledons > herbaceous dicotyledons > woody dicotyledons. In all three groups, RGR was strongly dependent upon LAR but no differences emerged in absolute scale of LAR. The absolute scale of mean LWF decreased for herbaceous to woody species, but the dependence of LAR on LWF strengthened. Groups showed on systematic differences in magnitude of SLA, but the correlation of LAR with SLA was strong throughout. Multiple regression showed that the leading determinants of RGR were ULR and SLA in herbaceous species and LWF in woody species. Principal components analyses (PCA) on each of the three groups explained at least 77% of variation and agreed closely with an optimal (non-hierarchical) classification. Only six cluster 'types' were recognized out of the 16 theoretically possible combinations of 'high' or 'low' values of the four growth parameters. Strong evidence of evolutionary trade-offs emerged, most strikingly in that high RGR was never seen in combination with low SLA. The morphological/physiological types identified by an all-groups PCA separated woody from the herbaceous species, but dicotyledons were almost congruent with the monocotyledons. The non-growth-analytical attributes most strongly correlate with mean RGR were percentage yield at a low level of mineral nutrients, leaf nitrogen concentration, and seed weight. it was concluded that mean RGR plays a central role in the identification of pathways of evolutionary specialization in herbaceous species. [ABSTRACT FROM AUTHOR]

We studied the effect of temperature on nectar secretion in Thymus capitatus, a typical labiate of phrygana (i.e. the garrigue of the East Mediterranean Basin). Experiments were carried out at controlled temperatures in a climatic chamber. We measured the nectar standing crop of the flowers at the end of the first day of their anthesis. All nectar values (i.e. volume per flower, sugar content and concentration) increased with temperature up to 38 °C, as long as the plants were not water stressed. However, in the open and under normal temperate conditions (i.e. at relatively low temperatures) nectar secretion depended more on changes in solar irradiance than on temperature. Under the same conditions, nectar secretion in Ballota acetabulosa, a species that is sympatric and coflowering with T. capitatus, was affected neither by light nor temperature. Since in the wild these two species are found in different microhabitats (full sun and shade, for T. capitatus and B. acetabulosa, respectively), we attribute the differences we observed to the differential natural adaptation of the plants to these factors. We conclude that T. capitatus is very well adapted to the Mediterranean conditions. By performing optimally as a nectar source at high temperatures, it can support a very large insect fauna that visits its flowers for nectar. It is in fact a temperature-induced cornucopian species. [ABSTRACT FROM AUTHOR]

Stolon growth and branching in Glechoma hederacea L. was analyzed, using a plastochron index based on the number of ramets on each stolon and internode growth. New methods, employing this index, were used to detect fluctuations in the rate of stolon extension, and to analyse the development of secondary stolons. The plastochron index had a strong linear correlation with time, with a new primary ramet appearing every 3.5 d. The overall stolon extension rate fluctuated between 1.9 and 2.9 cm d-1 through each plastochron cycle. The age at which each node produced secondary stolons was related to its position on the plant, but the initial rates of secondary stolon development differed little between nodes. Rate of development of secondary stolons was strongly correlated with the time at which they started to grow. Thus, later developing secondary stolons grew more slowly than those developing earlier from nodes in equivalent positions. [ABSTRACT FROM AUTHOR]

The isoetid life-form was originally defined on morphological grounds and subsequent physiological investigations showed that all of the isoetids examined took up a large fraction of the inorganic C fixed in their leaves from the root medium under natural conditions and that some of them carried out much of their assimilation of inorganic C via a CAM-like mechanism. Root-dominated uptake of inorganic C appeared to be unique to, and ubiquitous in, the isoetids. However, a large capacity for CAM-like metabolism in submerged vascular plants is not universal in isoetids, nor is it restricted to this life-form, being also found in Crassula aquatica.

Two experiments were conducted in which the influence of size of clones and the persistence of stolon connections on subsequent development were examined in Glechoma hederacea. In the first experiment, clones were grown from either one unrooted ramet or from either one, two or three connected, rooted ramets, for 8 weeks, in either nutrient-rich or nutrient-poor sand. The survival, number of ramets and dry weight of the clones produced were dependent on the number of established ramets at the start of the experiment. Clones in nutrient-rich sand developed a greater number of ramets, stolon branches, total length of stolon, mean leaf area per ramet and total leaf area per clone than clones of corresponding initial size in nutrient-poor sand. In the second experiment, the stolon connections between ramets of G. hederacea clones growing in boxes were either left intact or severed soon after each ramet had rooted. After 10 weeks of growth, the total dry weight of the intact clones and the mean dry weight of their ramets were significantly greater than the corresponding values for severed clones. The spatial distribution of ramets showed marked differences between the treatments. Severed clones produced a greater number of rooted ramets within the boxes and a smaller number of unrooted ramets beyond the box edges than intact clones. Density of ramets more than doubled when stolons were severed. Maintenance of stolon connections in G. hederacea is advantageous because it improves the probability of daughter ramet survival, promotes rapid lateral expansion of the clone and reduces inter-ramet competition through the production of fewer, larger ramets. [ABSTRACT FROM AUTHOR]

The growth of Plantago lanceolata L. has been described using metamers as construction units. The growth of each unit has been broken down into a sequence of four simple building instructions, two of which incorporate two or three alternatives. The resulting conceptual model has been tested against a variety of teratologies known to exist in Plantago lanceolata. All of these malformations could be explained in terms of either wrong steps, or wrong sequences, or both. There seems to be a certain hierarchy of control such that more malformations tend to occur at tertiary meristems than at primary meristems. For at least some of the teratologies, the nature of the control seems genetic. [ABSTRACT FROM AUTHOR]

In vivo nitrate reductase (NR) activity was measured in the leaves of plants from woodland, wooland-edge and open (ruderal) communities, Nitrate reductase activity was highest in the youngest fully-expanded leaves of all plants sampled. Nitrate reductase activity in populations from woodland and woodland-edge increased after feeding with nitrate; feeding with Mo had no significant effect. During the day NR activity in plants from each community increased to a maximum near the middle of the photoperiod and then decreased. These daily changes are discussed in terms of the possible regulatory roles of light and the transport of nitrate to the shoot. [ABSTRACT FROM AUTHOR]

Following an outline of the great variation in the primitive cultivars and wild species of potatoes in Latin America, the history of introductions and breeding procedures is discussed. Although two introductions occurred in the 16th century there were only few early introductions, and only very few varieties were grown in the early 18th century. The appearance of virus diseases, which debilitated established varieties but did not pass through true seed, led to widespread selection among seedlings and a vast increase in the number of varieties grown in the late 18th and early 19th centuries. The seedlings were from naturally-set berries and most would be selfed derivatives; selection among them may have reduced the gene-pool. Improvements made by this selection were such that most 19th century introductions appeared primitive and, with only two known exceptions, they were discarded. Blight appeared in the mid 19th century and eliminated almost all varieties, including a number which were probably virus resistant, thus further reducing the gene-pool. T. A. Knight commenced deliberate crossing before 1810 but this practice did not become widespread until the second half of the 19th century. Breeding among the few survivors of the blight epidemics and the few new introductions led, by the early 20th century, to a great many varieties being grown, e.g. over 500 in Britain and over 50 in North America, but they represented only a very limited gene-pool. The pedigrees of modern potato varieties show that, although several 20th century introductions may occur in their ancestries, generally 80% or more of their genes are derived from varieties grown early this century. An appendix illustrates this for the recent varieties Pentland Dell and Croft. It follows that the gene-pool is still rather limited, and that modern varieties are somewhat inbred due to relationships between their parents and ancestors. [ABSTRACT FROM AUTHOR]

The pattern of uptake of copper by plants of Mimulus guttatus that are either homozygous tolerant, homozygous non-tolerant, or heterozygous tolerant, was compared. Tolerant plants took up more copper, particularly into the roots, and root uptake by the homozygote tolerant was greater than the heterozygote. Plants of all three genotypes took up increasing quantities of copper to their roots until day 7, but no further increase was obtained by day 11. The physiological implication of these results is discussed. [ABSTRACT FROM AUTHOR]

Besides species of Eucalyptus, Leptospermum, Casuarina and Pomaderris which are known to from ectomycorrhizas, many other Australian native plants may form ectomycorrhizal associations. The plants include many legumes, especially in the tribe Podalyrieae of the Fabaceae and Acacia in the Mimosaceae, all members of the Rhamnaceae examined, and species of such diverse genera as Opercularia, Poranthera, Platysace, Goodenia and Stylidium. Many, perhaps most, of these ectomycorrhizal plants may also form endomycorrhizas of the VA type. The ectomycorrihizal species range from large forest trees to small non-woody herbs. The associations vary from well-defined mycorrhizas of the beech type to looser ones of a continuous or partial sheath, with or without a Hartig net. In soil low in available phosphate both typical and Looser ectomycorrhizal associations markedly increased plant growth compared with that of uninoculated plants. [ABSTRACT FROM AUTHOR]

Water potentials, osmotic potentials and stomatal resistances were measured daily in a growth room during a 16-day period, in growing leaves of a drought-sensitive and a drought-resistant winter wheat (Tritictim aestivum L. em. Thell.), which had the roots maintained under one of three root-temperature treatments: (1) constant temperature of 24 °C (about the optimum); (2) constant temperature of 34 °C (10° above the optimum and near the high temperature limit for growth); and (3) alternating temperature of 24 h at 24 °C followed by 24 h at 34 °C. Air temperature was constant at 24 °C. Water and osmotic potentials, stomatal resistances, and height of plants maintained at the 34 °C root temperature were intermediate between those grown at 24 °C (highest potentials, lowest resistances, tallest) and those alternated daily between the two temperatures (lowest potentials, highest resistances, shortest). Previous work showed that potentials, stomatal resistances, and growth of wheats subjected to constant root temperatures of 25, 29 and 33 °C were linearly related to root temperature with lowest potentials, highest resistances, and least growth at the high temperature. Even though alternated plants in this experiment were at an average root temperature of 29 °C, they grew the poorest. The wheat plants, therefore, did not integrate a root temperature stress in the same manner over 'time' as they did over 'space'. The results showed that the stomatal resistance, water and osmotic potentials, and height of wheat seedlings, maintained at a constant root temperature 10 °C higher than the optimum, were about halfway between those of plants grown at the optimum and those alternated daily between the optimum and the optimum-plus-10 °C root temperature. [ABSTRACT FROM AUTHOR]

The development of photosynthetic activity in cotyledons from non-dormant apple embryos and embryos in a state of dormancy was studied during the culture of intact embryos, of single cotyledon with axis, and of isolated cotyledons. The embryonal axis was found to stimulate the development of photosynthetic activity in the cotyledons. In non-dormant embryos the influence of the axis on the assimilation of CO2 by cotyledons became apparent at an early stage of culture; in the dormant embryos it was noted first after 10 to 12 days. No influence of the embryonalaxis was observed on chlorophyll biosynthesis in cotyledons. The photosynthetic rate was always higher in cotyledons from non-dormant embryos than in those from dormant ones. However, the chlorophyll content was similar in cotyledons from both groups of embryos. It is concluded that the interaction of the embryonal axis and cotyledons in the development of photosynthetic activity in seedlings depends on the physiological state of the embryo. [ABSTRACT FROM AUTHOR]

The sequence of ultrastructural changes which take place during chloroplast development in leaves of plants of Phaseolus vulgaris grown in the light is compared with that of plants grown in the dark. Further comparisons are made with the developmental sequence found in the hypocotyls of Phaseolus and in the leaves of Zea mays. It is concluded that there is a single basic pathway of chloroplast development. Variations in this pathway are related to blocks in the sequence resulting in the accumulation of storage materials such as phytoferritin and prolamellar bodies, characteristic of the species or tissue concerned. An attempt has been made to assess the ubiquity and duration of an association between plastids and the E.R. in lower plant species compared with the angiosperms. A plastid-E.R. association is common and persistent in lower plant species whereas in angiosperms it is apparently transitory and confined to immature or specialized cells. [ABSTRACT FROM AUTHOR]

Gibberellin A[sub1] breaks the dormancy of hazel seed. Both GA[sub1] and GA[sub3] are transported more readily from embryonic axis to cotyledon than in the reverse direction. Since both gibberellins stimulate axis growth more rapidly when applied directly to it than when applied to the cotyledon, it seems likely that gibberellins directly affect the axis. This is confirmed by a rapid response of excised axes to gibberellic acid in liquid culture. [ABSTRACT FROM AUTHOR]

The presence of a number of pentose phosphate pathway (PPP) enzymes in developing barley endosperm is reported. The relative importance of the Embden-Meyerhof-Parnas pathway (EMPP) and the PPP throughout endosperm development was assessed by following the changes in activity of five EMPP and four PPP enzymes. The patterns of activity of the EMPP enzymes were very similar with pronounced peaks of activity at 35 days after anthesis thereafter falling to low or zero levels at the onset of maturity. The PPP enzymes, on the other hand, rose to maximum levels around 30-35 days falling only slightly thereafter. [ABSTRACT FROM AUTHOR]

Recent developments in the classification of the earliest vascular plants are discussed. The fertile parts of Hicklingia edwardii, a remarkably well preserved plant from the Middle Old Red Sandstone of Scotland, are described. It is concluded that this plant had lateral not terminal sporangia and may be assigned provisionally to the Zosterophyllophytina until more is known about its anatomy. [ABSTRACT FROM AUTHOR]

It is suggested that the functional significance of each di/trimorphic structure in heterostyled flowers should be considered separately. The origin of the morphological and physiological components of heterostyly is discussed; it is suggested that the physiological incompatibility arose first and created conditions favouring selection of morphological differentiation. In this connection, the cases of Amsinckia and Narcissus tazetta are given special consideration. The restricted occurrence of tristyly is considered together with the distinctive syndrome of exserted sexual organs and sternotribic pollination in heterostyled plants. The need is emphasized to bear in mind constantly the functional aspects of heterostyly. [ABSTRACT FROM AUTHOR]

Seedlings of the shade-tolerant species, Deschampsia flexuosa, were subjected to shade treatments under controlled conditions of daylength, temperature, irradiance, relative humidity and mineral nutrient supply. Dry matter production was compared with that of seedlings of the shade-intolerant species, Agrostis tenuis and Festuca ovina. The three species did not differ markedly with respect to their light intensity compensation points. A more promising explanation for the shade tolerance of Deschampsia flexuosa lies in the extremely low negative relative growth rates which seedlings exhibit at light intensities below the compensation point. [ABSTRACT FROM AUTHOR]

Heteranthelium is a monotypic genus in the tribe Triticeae represented by an annual diploid species, H. piliferum. The spike of this species is quite different from other members of the tribe. In an attempt to elucidate the genetic relationships to other genera of the tribe, H. piliferum was crossed with various species of Aegilops, Agropyron, Eremopyrum, Henrardia and Hordeum. From these crosses F1 hybrids of (1) Heteranthelium piliferum (2x) × Eremopyrum bonaepartis (2x) and (2) Heteranthelium piliferum × Hordeum depressum (4x) were produced. At the same time F1 hybrids of (3) Eremopyrum bonaepartis × Hordeum depressum was also obtained. The hybrid under (1) showed subnormal growth and the shape of the spikes was of Eremopyrum-type, while the spikelets were intermediate. Growth of the hybrid under (2) was vigorous and the spike morphology was intermediate between the parents. A solitary spikelet with two glumes and a single spikelet at each rachis node like the Heteranthelium parent was observed but no rudimental spikelets which are the characteristic of Heteranthelium were found. Growth of the hybrid under (3) was very vigorous and the shape of the spikes was of Hordeum type. However, floral construction at each rachis node was very complicated. Rachis nodes with three glumes and a single spikelet were the most common. Sterility of all three combinations was complete. Average chromosome pairing per cell of the F1 hybrids was in (1) 0.04 bivalents and 13.93 univalents, in (2) 0.00 trivalents, 5.06 bivalents and 10.88 univalents, and in (3) 0.00 quadrivalents, 0.01 trivalents, 5.50 bivalents and 9.97 univalents. Judging from the chromosome pairing in (1), (2) and (3), a high bivalent formation in (2) and (3) is attributable to autosynthesis of chromosomes derived from the Hordeum parent. It is concluded that there is no homology among the genomes of those three species. Considering morphological features, geographical distribution, intergeneric cross-ability and genetic relationships of Heteranthelium piliferum, it is concluded that the monotypic genus Heteranthelium is a distinct entity in the tribe Triticeae. This taxon has evolved as an annual during the process of adaptation to rather dry habitats of the Mediterranean climatic regions in the course of generic differentiation of the tribe. [ABSTRACT FROM AUTHOR]

The gynoecium of Coriaria ruscifolia is made up of five carpels joined in their lower parts. It is interpreted as syncarpous, not apocarpous, and is considered to represent five peltate carpels free above a very short ventral split and joined narrowly below the split along their median parts, as by so many longitudinal strips. The free part of each carpel consists of the unifacial style (without ventral split) and its short junction with the associate part of the carpel at the level of the ventral split. The joined parts are the ascidiate regions of the carpels with their solid basal union. The study of phyllodic gynoecia enables us to discover the homologies between carpel and leaf in Coriaria and to explain more clearly the peltation concept, which appears to have been misunderstood by English-speaking botanists. [ABSTRACT FROM AUTHOR]

The article focuses the use of network theory in understanding the nature arbuscular mycorrhizal (AM) fungi-plant interactions. It discusses Chagnon and colleagues and Montesinos-Navarro and colleagues' research and arguments concerning bipartite networks. It also recall the basic theory on interaction matrix and the basic facts implying that co-occurrence ≠ interaction.

In this article, the authors look forward to trends in plant science in 2007. The authors provide a glimpse of a future with new and emerging opportunities in plant science research. They indicate that very large data sets of biological information will increasingly underpin new synthetic and systems understanding. They also project that interactions between plants and other organisms are important but difficult to study.