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At least 145 records · Page 8Linked to original sources

PubMed2003

Evaluation of mycelial inocula of edible Lactarius species for the production of Pinus pinaster and P. sylvestris mycorrhizal seedlings under greenhouse conditions.

Different methods to inoculate seedlings of Pinus pinaster and P. sylvestris with edible Lactarius species under standard greenhouse conditions were evaluated. Fungal inoculations were performed both under pure culture synthesis in vitro, followed by transplantation of acclimatized seedlings, and directly in the greenhouse using different techniques for inocula production (mycelial slurries, vegetative inoculum grown in peat-vermiculite and alginate-entrapped mycelium). In vitro inoculations with L. deliciosus produced thoroughly colonized seedlings. However, a sharp decrease in mycorrhizal colonization was detected on transplanted seedlings after 4 month's growth in the greenhouse. On the other hand, all the inocula applied directly in the greenhouse, except the alginate-entrapped mycelium, produced a variable number of mycorrhizal seedlings and colonization rates after the first growing season, depending on the plant-fungal combination and the inoculation method. Inoculations with vegetative inocula of the strain 178 of L. deliciosus were the most effective in producing mycorrhizal seedlings. All the seedlings inoculated with this strain were colonized although the colonization rates were relatively low. The commercial feasibility of the different inoculation methods for the production of seedlings colonized with edible Lactarius species is discussed.

Agaricales↗

PubMed2003

Resprouting ability of Quercus crispula seedlings depends on the vegetation cover of their microhabitats.

To examine the effects of vegetation cover on the resprouting abilities of Quercus crispula seedlings, in each of three consecutive years, we artificially clipped seedlings growing in microhabitats with differing degrees of vegetation cover. We also investigated the relationship between the level of total nonstructural carbohydrate (TNC) and resprouting ability. Seedlings with clipped shoots in gaps produced larger resprouting shoots than those in the understory. Moreover, both the percentage of resprouting seedlings and the survival ratio in seedlings with clipped shoots were negatively correlated with the degree of vegetation cover. Seedlings stored high levels of TNC, especially in their roots, and their TNC levels were negatively correlated with the degree of vegetation cover. There were also positive relationships between the TNC levels in their roots and the degree of resprouting. Hence, we conclude that release from vegetation cover enhanced the resprouting ability of Q. crispula seedlings by increasing their levels of stored carbohydrate. The key variables affected were the resprouting ratio (the proportion of seedlings capable of producing new shoots) and the size of the resprouted shoots.

Biomass↗

PubMed2006

The use of compost in afforestation of Mediterranean areas: Effects on soil properties and young tree seedlings.

In Mediterranean frequently burnt areas, fire and erosion result in the decrease of soil fertility, so afforestation is a major concern. We carried out an in situ experiment of compost amendment to improve survival and growth of planted tree seedlings. One-year-tree seedlings of native species (Quercus ilex, Pinus halepensis and Pinus pinea) were planted on a frequently burnt calcareous site. Three rates of fresh co-composted sewage sludge and greenwastes (control without compost, 20 and 40 kg m(-2) of compost) were incorporated into the soil at each seedling stem. Changes of soil properties and tree development were studied during 3 years (2001-2003) and 2 years (2002-2003) respectively. The compost improved survival of Quercus ilex and Pinus pinea seedlings in severe drought conditions, but had no effect on Pinus halepensis. For all species seedling length and radial growth and NPK nutrition were increased for both rates of amendment. Amendment improved soil fertility, but available P concentration increased 13 fold in the neighbouring soil of seedlings amended at the maximal rate compared to control. However, amendment did not significantly increase concentrations of Cd, Cr, Ni and Pb in soils or tree seedlings. It increased Cu and Zn total and available concentrations in soils, while foliar Cu and Zn concentrations in the seedlings remained similar in all plots. Compost can efficiently help afforestation of dry soils with low organic matter content. However, sewage sludge concentrations in P, and to a lesser extent in Cu and Zn, limit rates of application that can be applied without environmental hazard.

Agriculture↗

PubMed2004

Apoptosis in wheat seedlings grown under normal daylight.

Apoptosis was observed in the coleoptile and initial leaf in 5-8-day-old wheat seedlings grown under normal daylight. Apoptosis is an obligatory event in early wheat plant ontogenesis, and it is characterized by cytoplasmic structural reorganization and fragmentation, in particular, with the appearance in vacuoles of specific vesicles containing intact organelles, chromatin condensation and margination in the nucleus, and internucleosomal fragmentation of nuclear DNA. The earliest signs of programmed cell death (PCD) were observed in the cytoplasm, but the elements of apoptotic degradation in the nucleus appeared later. Nuclear DNA fragmentation was detected after chromatin condensation and the appearance in vacuoles of specific vesicles containing mitochondria. Two PCD varieties were observed in the initial leaf of 5-day-old seedlings grown under normal daylight: a proper apoptosis and vacuolar collapse. On the contrary, PCD in coleoptiles under various growing (light) conditions and in the initial leaf of etiolated seedlings is only a classical plant apoptosis. Therefore, various tissue-specific and light-dependent PCD forms do exist in plants. Amounts of O2*- and H2O2 evolved by seedlings grown under normal daylight are less than that evolved by etiolated seedlings. The amount of H2O2 formed in the presence of sodium salicylate or azide by seedlings grown under normal daylight was increased. Contrary to etiolated seedlings, the antioxidant BHT (ionol) did not inhibit O2*- formation and apoptosis and it had no influence on ontogenesis in the seedlings grown under normal daylight. Thus, in plants grown under the normal light regime the powerful system controlling the balance between formation and inactivation of reactive oxygen species (ROS) does exist and it effectively functions. This system is responsible for maintenance of cell homeostasis, and it regulates the crucial ROS level controlling plant growth and development. In etiolated plants, this system seems to be absent, or it is much less effective.

Antioxidants↗

PubMed2004

Comparative seedling ecology of eight North American spruce (Picea) species in relation to their geographic ranges.

BACKGROUND AND AIMS: Allowing for dispersal limitation, a species' geographic distribution should reflect its environmental requirements. Comparisons among closely related species should reveal adaptive differentiation in species characteristics that are consistent with their differences in geographic distribution. This expectation was tested by comparing characteristics of seedlings of spruce species in relation to environmental factors representative of their current natural ranges. METHODS: Seedlings were grown from a total of 34 populations representing eight North American spruce (Picea) species in a controlled environment chamber for 140 d. Traits related to the potential of seedling establishment, including tolerance to stress events (high temperature, desiccation) were evaluated. Correlations were sought between these characteristics and modal values of latitude, aridity and continentality in the geographic range of each species. KEY RESULTS: Many seedling traits changed significantly in response to stress events, but only the response of chlorophyll concentration differed significantly among species. Components of seedling growth were good correlates of species distribution. Seedling relative growth rate (RGR) and specific leaf area (SLA) were positively correlated with latitude, and leaf weight ratio (LWR) negatively correlated with aridity. Seed mass was negatively correlated with latitude. CONCLUSIONS: Relationships found between seedling traits and geographical variation in environmental conditions suggest that factors such as temperature regime, water availability and perhaps litter depth affect species range in North American spruces. Seedling characteristics appear to be elements in a reasonably distinct environmental niche for each spruce species at the continental scale.

Chlorophyll↗

PubMed2004

Comparison of QTL controlling seedling vigour under different temperature conditions using recombinant inbred lines in rice (Oryza sativa).

BACKGROUND AND AIMS: Seedling vigour is one of the major determinants for stable stand establishment in rice (Oryza sativa), especially in a direct seeding cropping system. The objectives of this study were to identify superior alleles with consistent effects on seedling vigour across different temperature conditions and to investigate genotype x environmental temperature interactions for seedling vigour QTL. METHODS: A set of 282 F13 recombinant inbred lines (RILs) derived from a rice cross were assessed for four seedling vigour traits at three temperatures (25 degrees C, 20 degrees C and 15 degrees C). Using a linkage map with 198 marker loci, the main-effect QTL for the traits were mapped by composite interval mapping. KEY RESULTS: A total of 34 QTL for the four seedling vigour traits were identified. Of these QTL, the majority (82%) were clustered within five genomic regions, designated as QTL qSV-3-1, qSV-3-2, qSV-5, qSV-8-1 and qSV-8-2. All of these five QTL had small individual effects on the traits, explaining 3.1-15.8 % of the phenotypic variation with a mean of 7.3 %. QTL qSV-3-1, qSV-3-2 and qSV-8-1 showed almost consistent effects on the traits across all three temperatures while qSV-5 and qSV-8-2 had effects mainly at the 'normal' temperatures of 20 degrees C and 25 degrees C. Among the five QTL identified, all and four showed additive effects on shoot length and germination rate, respectively. The contributions of these five QTL to shoot length and germination rate were also much larger than those to the other two traits. CONCLUSIONS: A few of genomic regions (or QTL) were identified as showing effects on seedling vigour. For these QTL, significant genotype x environmental temperature interactions were found and these interactions appeared to be QTL-specific. Among the four seedling vigour traits measured, shoot length and germination rate could be used as relatively good indicators to evaluate the level of seedling vigour in rice.

Chromosome Mapping↗

PubMed2004

Morphological and physiological responses of beech (Fagus sylvatica) seedlings to grass-induced below ground competition.

We examined morphological and physiological responses of beech (Fagus sylvatica L.) seedlings to grass-induced below ground competition in full-light conditions. Two-year-old beech seedlings were grown during two growing seasons in 160-l containers in bare soil or with a mixture of five grass species widely represented in semi-natural meadows of central France. At the end of the second growing season, beech seedlings in the presence of grass showed significant reductions in diameter and height growth, annual shoot elongation, and stem, root and leaf biomass, but an increase in root to shoot biomass ratio. Grasses greatly reduced soil water availability, which was positively correlated with daily seedling diameter increment. Beech seedlings seemed to respond to water deficit by anticipating stomatal closure. There was evidence of competition for nitrogen (N) by grasses, but its effect on seedling development could not be separated from that of competition for water. By labeling the plants with 15N, we showed that beech seedlings absorbed little N when grasses were present, whereas grasses took up more than 97% of the total N absorbed in the container. We conclude that, even if beech seedlings display morphological and physiological adaptation to below ground competition, their development in full-light conditions may be strongly restricted by competition from grass species.

Biomass↗

PubMed2005

Ontogenetic transition of leaf physiology and anatomy from seedlings to mature trees of a rain forest pioneer tree, Macaranga gigantea.

In a field study, we compared anatomy and diurnal gas exchange and chlorophyll fluorescence in sunlit mature leaves of Macaranga gigantea (Reichb. f. and Zoll.) Muell. seedlings, saplings, an adult tree and suckers originating from stumps. We tested the hypothesis that the pattern of resource use shifts across various life stages with ontogenetic changes in leaf anatomy and physiology. Among leaves of different developmental stages, seedling leaves were the smallest and thinnest, whereas adult tree leaves were the largest and thickest, and the air space within the lamina was largest in seedling leaves and smallest in adult tree leaves. Photosynthetic nitrogen-use efficiency (PNUE) was higher in seedling and sapling leaves than in adult tree leaves. Mean PNUE in seedling leaves was 1.6 times that in adult tree leaves. Nevertheless, among the developmental stages, net photosynthetic rate (Pn) per unit leaf area was lowest in seedling leaves because they have the lowest nitrogen (N) content per unit leaf area. In situ water vapor stomatal conductance (g(s) at a given leaf-to-air vapor pressure deficit was highest in sapling leaves, suggesting that they have a high hydraulic efficiency per unit leaf area. Among developmental stages, intrinsic water-use efficiency (Pn/g(s)) and photochemical capacity of photosystem II were lowest in seedling leaves. Sapling leaves had the highest N concentration and Pn per unit dry mass and the highest g(s), indicating that the gradual transition from the seedling stage to the sapling stage is accompanied by an accumulation of N in plant bodies and the development of hydraulic systems to counteract unfavorable environmental stresses. The properties of adult tree leaves (low PNUE, high carbon:N ratio, small and dense cells and thick lamina) indicate that, during the transition from the sapling stage to the adult tree stage, the priority of resource use in leaves gradually shifts from enhancement of photosynthetic performance to defense against herbivory and mechanical damage. Leaf morphology and physiology were coordinated with the differences in resource use at each life stage.

Carbon Dioxide↗

PubMed2006

Ectomycorrhizal networks and seedling establishment during early primary succession.

Ectomycorrhizal (ECM) fungal mycelia are the main organs for nutrient uptake in many woody plants, and often connect seedlings to mature trees. While it is known that resources are shared among connected plants via common mycorrhizal networks (CMNs), the net effects of CMNs on seedling performance in the field are almost unknown. CMNs of individual ECM fungal species were produced in an early succession volcanic desert by transplanting current-year seedlings of Salix reinii with ECM mother trees that had been inoculated with one of 11 dominant ECM fungal species. Most seedlings were connected to individual CMNs without being infected by other ECM fungi. Although control seedlings showed poor growth under severe nutrient competition with larger nonmycorrhizal mother trees, nutrient acquisition and growth of seedlings connected to CMNs were improved with most fungal species. The positive effects of CMNs on seedling performance were significantly different among ECM fungal species; for example, the maximum difference in seedling nitrogen acquisition was 1 : 5.9. The net effects of individual CMNs in the field and interspecific variation among ECM fungal species are shown.

DNA, Ribosomal↗

PubMed2004

Molecular profiling of rhizosphere microbial communities associated with healthy and diseased black spruce (Picea mariana) seedlings grown in a nursery.

Bacterial and fungal populations associated with the rhizosphere of healthy black spruce (Picea mariana) seedlings and seedlings with symptoms of root rot were characterized by cloned rRNA gene sequence analysis. Triplicate bacterial and fungal rRNA gene libraries were constructed, and 600 clones were analyzed by amplified ribosomal DNA restriction analysis and grouped into operational taxonomical units (OTUs). A total of 84 different bacterial and 31 different fungal OTUs were obtained and sequenced. Phylogenetic analyses indicated that the different OTUs belonged to a wide range of bacterial and fungal taxa. For both groups, pairwise comparisons revealed that there was greater similarity between replicate libraries from each treatment than between libraries from different treatments. Significant differences between pooled triplicate samples from libraries of genes from healthy seedlings and pooled triplicate samples from libraries of genes from diseased seedlings were also obtained for both bacteria and fungi, clearly indicating that the rhizosphere-associated bacterial and fungal communities of healthy and diseased P. mariana seedlings were different. The communities associated with healthy and diseased seedlings also showed distinct ecological parameters as indicated by the calculated diversity, dominance, and evenness indices. Among the main differences observed at the community level, there was a higher proportion of Acidobacteria, Gammaproteobacteria, and Homobasidiomycetes clones associated with healthy seedlings, while the diseased-seedling rhizosphere harbored a higher proportion of Actinobacteria, Sordariomycetes, and environmental clones. The methodological approach described in this study appears promising for targeting potential rhizosphere-competent biological control agents against root rot diseases occurring in conifer nurseries.

Bacteria↗

PubMed2003

Evaluation of growth potential of Crimean juniper (Juniperus excelsa Bieb.) seedlings for the first growing season under Tekir forest nursery conditions in Kahramanmaras, Turkey.

In this study, growth potential of Crimean juniper (Juniperus excelsa Bieb.) seedlings for the first growing season under Tekir Forest Nursery conditions in Kahramanmaras was evaluated. The height growth of Crimean juniper seedlings was relatively close to that of Lebanon cedar (Cedrus libani A. Rich.) seedlings produced in the same nursery, but their root collar diameters were fairly lower than that of Lebanon cedar seedlings. According to coniferous seedling standards of Turkish Standards Institute, the height growth of Crimean juniper seedlings was fairly good, but their root collar diameters were slightly small. In this respect, that 2+0 or 1+1 Crimean juniper seedlings are used in reforestation activities in the region would be more useful than 1+0 seedlings.

Conservation of Natural Resources↗

PubMed2006

[Adaptation strategies of seed germination and seedling growth to sand dune environment].

Sand dune plants possess many adaptation strategies to withstand sand environment, e. g., some desert plant seeds are dormant when matured, which helps them to escape from unfeasible environment conditions and be preserved as seed bank. The seed germination and seedling establishment of psammophytes need moderate sand burial, while excessive burial will inhibit seed germination and seedling emergence. Seeds without germination in deeper sand are in enforced dormancy, and form soil seed bank. Sand dune plant seedlings could tolerant finite sand burial by increasing the number of nodes per culm and elongating internodes. When the seedlings are partially buried, they could survive through the maintenance of photosynthesis organism. Once sand burial exceed the threshold of the plant, seedlings growth will be restrained and the growth ability even permanently lost. Other factors such as salt spray, insect herbivory, and lack of soil nutrients also affect seed germination and seedling establishment. The precipitation in desert and sand land is unpredictable and irregular. Sand erosion leads roots be exposed to the air and dehydrated to die. However, seedlings of some desert plant have the ability to tolerate desiccation for a period of time after germination. Once there is rain, the seedlings will rivive.

Adaptation, Physiological↗

PubMed1991

Water deficit modulates gene expression in growing zones of soybean seedlings. Analysis of differentially expressed cDNAs, a new beta-tubulin gene, and expression of genes encoding cell wall proteins.

Transfer of soybean seedlings to low-water-potential vermiculite (psi w = -0.3 MPa) results in a reversible decrease in hypocotyl growth and modulation of several polysomal mRNAs (Plant Physiol 92: 205-214). We report here the isolation of two cDNA clones (pGE16 and pGE95) which correspond to genes whose mRNA levels are increased, and one cDNA clone (pGE23) which corresponds to a gene whose mRNA level is decreased in the hypocotyl zone of cell elongation by water deficit. In well-watered seedlings mRNAs hybridizing to pGE16 and pGE95 are most abundant in mature regions of the seedling, but in water-deficient seedlings mRNA levels are reduced in mature regions and enhanced in elongating regions. RNA corresponding to soybean proline-rich protein 1 (sbPRP1) shows a similar tissue distribution and response to water deficit. In contrast, in well-watered seedlings, the gene corresponding to pGE23 was highly expressed in the hypocotyl and root growing zones. Transfer of seedlings to low-water-potential vermiculite caused a rapid decrease in mRNA hybridizing to pGE23. Sequence analysis revealed that pGE23 has high homology with beta-tubulin. Water deficit also reduced the level of mRNA hybridizing to JCW1, an auxin-modulated gene, although with different kinetics. Furthermore, mRNA encoding actin, glycine-rich proteins (GRPs), and hydroxyproline-rich glycoproteins (HRGPs) were down-regulated in the hypocotyl zone of elongation of seedlings exposed to water deficit. No effect of water deficit was observed on the expression of chalcone synthase. Decreased expression of beta-tubulin, actin, JCW1, HRGP and GRP and increased expression of sbPRP1, pGE95 and pGE16 in the hypocotyl zone of cell elongation could participate in the reversible growth inhibition observed in water-deficient soybean seedlings.

Actins↗

PubMed1995

Effects of acid rain on growth and nutrient concentrations in Scots pine and Norway spruce seedlings grown in a nutrient-rich soil.

The effects of artificially applied acid precipitation on growth and nutrient concentrations of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst.) seedlings were investigated in a long-term acid irrigation experiment in field conditions. Seedlings of northern and southern origin were planted in boxes containing peat and composted soil rich in nutrients, and sprinkler irrigated with water acidified with nitric and sulphuric acids to pH 3 or pH 4 for periods varying from two to three and a half growing seasons during 1986-1989. Water irrigated (pH 5.4-7.6) and non-irrigated groups of seedlings were also included in the experiment. At the end of the experiment needles, main and lateral shoots and roots were collected from the seedlings for the determination of height growth and biomass partitioning, and for the analysis of S, N, Mg, P, K, Ca, Mn and Fe concentrations. The treatment effects compared to the irrigated control were studied using multivariate analyses of variance and covariance. In the pine seedlings the total dry matter production increased by 25-70% compared with the irrigated controls when the total wet deposition to the seedlings exceeded 67 kg S ha(-1) and 36 kg N ha(-1) (e.g. after two growing seasons' exposure of the pH 3 treatment). The increase was mainly due to an increase in needle dry weight (54-72% greater at pH 3) and root weight (20-65% greater at pH 3), whereas the height growth or shoot weight growth were less affected. The northern provenance pine seedlings responded more clearly to the pH 3 irrigation than the southern ones. The treatments had no consistent effects on any of the growth variables studied in the spruce seedlings, however. The pines had higher root and foliage Ca concentrations as a result of the acid irrigation, whereas in spruce, acid rain decreased the Ca concentration in needles and shoots. Root Mn and Fe concentrations were higher in both species as a result of the pH 3 treatment. A higher soil conductivity and Ca concentration resulted from the prolonged pH 3 treatment. The results strongly support the hypothesis that the long-term growth and nutrient allocation response of conifers to acid precipitation is dependent both on the tree species and on the nutritional status of the soil.

Journal Article↗

PubMed2002

Dynamic changes in cell wall polysaccharides during wheat seedling development.

Changes in arabinoxylan content and composition during development of wheat seedlings were investigated. The cell walls isolated from the seedlings showed an increasing content of arabinoxylan during development, which could be correlated to increased activity of xylan synthase and arabinoxylan arabinosyltransferase. Arabinoxylan changed from initially having a high degree of arabinose substitution to a much lower degree of substitution. beta-Glucan was present in the walls at the early stages of development, but was actively degraded after day 4. Increased deposition of arabinoxylan did not take place until beta-glucan had been fully degraded. Ferulic and p-coumaric acid esters were present at all points but increased significantly from day 3 to 6, where lignification began. Ferulic acid dimers did not appear in the cell wall until day three and the different ferulic acid dimers varied in the course of accumulation. The ratio of ferulic acid dimers to free ferulic acid was maximal at the time when the wall had been depleted for beta-glucan, which had not yet been fully replaced by arabinoxylan. This pattern suggests a role for ferulic acid dimers in stabilizing the wall during the transition from a flexible to a more rigid structure. To investigate if the same changes could be observed within a single seedling, 7 day old seedlings were divided into four sections and the walls were analyzed. Some of the changes observed during the seedling development could also be observed within a single seedling, when analyzing the segments from the elongation zone at the base to the top of the leaf. However, the expanding region of older seedlings was much richer in hydroxycinnamates than the expanding region of younger seedlings. Diferulic acids are stabilizing the wall in the transition phase from an expanding to a mature wall. This transition can take place in different manners depending on the cell and tissue type.

Cell Wall↗

PubMed1999

Genetic variation in postfire aspen seedlings in yellowstone national park

A rare episode of regeneration of aspen (Populus tremuloides Michx.) by seeds occurred in Yellowstone National Park (YNP), Wyoming, USA, following extensive fires that occurred in 1988. In 1997, we sampled 410 aspen seedlings from 23 local populations distributed widely across YNP to determine how genetic diversity varies with elevation, substrate, plant competition, ungulate browsing, and geographical location. We employed 132 randomly amplified polymorphic DNA (RAPD) markers based on six primers to show genetic relationships within and among the postfire aspen seedling populations. Measures of genetic variation, including estimates of percentage polymorphic loci, expected heterozygosity, and Nei's FST, indicated that most of the variation occurred within rather than among local populations. There was no indication of geographical differentiation among sampled populations based on hierarchal estimates of Nei's FST, neighbour-joining, or correlations between genetic distance and geographical distance. Even genetically distant populations shared nearly 90% of the same markers. Within plots, the amount of genetic variation decreased slightly in response to increased percentage vegetative cover, mean seedling basal diameter, and mean seedling height. Geological substrate, density of lodgepole pine (Pinus contorta var. latifolia Dougl.) seedlings, browsing intensity, and elevation were not significantly related to levels of genetic variation within the seedling plots. These data suggest that genetic variation and geographical structure among seedling populations may occur over time as the transition from seedling-dominated stands to clone-dominated stands occurs.

Journal Article↗

PubMed1992

Influence of a high Mn supply on Norway spruce (Picea abies (L.) Karst.) seedlings in relation to the nitrogen source.

Effects of 3, 25, 100, 200 and 800 microM Mn on biomass and pigment, starch and nitrate concentrations were studied in Norway spruce (Picea abies (L.) Karst.) seedlings grown with either NO(3) (-) or NH(4) (+) as the sole nitrogen source. After 77 days of exposure to 800 microM Mn, shoot growth had ceased in about 50% of the seedlings independently of the N source. Despite high Mn concentrations in roots and shoots of the Mn-treated seedlings, no visible symptoms of Mn toxicity were evident. The rate of root elongation was decreased by treatment with >/= 200 microM Mn when N was supplied as NO(3) (-), but not when it was supplied as NH(4) (+). This difference could be attributed to the higher Mn concentrations in root tips of the NO(3) (-)-grown seedlings compared with the NH(4) (+)-grown seedlings. In Mn-treated seedlings, the concentration of Mg, and to a lesser extent that of Ca, decreased. Depletion of these elements might account for the observed growth depression. Potassium concentrations were similar in the control and Mn-treated seedlings. Treatment of seedlings with 800 microM Mn for 50 days led to several physiological changes: starch accumulated, the concentrations of nitrate and phenolic compounds increased, pigment concentrations decreased, and in vivo nitrate reductase activity in roots was reduced.

Journal Article↗

PubMed1994

Influence of irradiance on photosynthesis, morphology and growth of mangosteen (Garcinia mangostana L.) seedlings.

The influence of shading intensity on growth, morphology and leaf gas exchange of mangosteen (Garcinia mangostana L.) seedlings was investigated over a 2-year period. Diurnal gas exchange studies revealed significantly higher carbon gain for leaves grown in 20 or 50% shade compared to leaves grown in 80% shade. Seedlings grown in 20 or 50% shade accumulated significantly more dry weight than seedlings grown in 80% shade during the 2-year study period. Seedlings grown in decreased shade showed decreased leaf size, increased leaf thickness, lower specific leaf area (SLA) and higher stomatal frequency. Less shaded seedlings also allocated relatively more dry matter to roots than shaded seedlings and exhibited a significant reduction in leaf area relative to total plant dry weight (leaf area ratio). Increased leaf number, enhanced branching and shorter internodes resulted in a more compact appearance of less shaded seedlings. Irrespective of light conditions, mangosteen seedlings exhibited inherently slow growth because of low photosynthetic rates per unit leaf area, low SLA, low leaf area ratios and inefficient root systems.

Journal Article↗