Showing papers on "Plant morphology published in 1998"

Close association of RGR, leaf and root morphology, seed mass and shade tolerance in seedlings of nine boreal tree species grown in high and low light

Abstract: Summary 1. To test hypotheses concerning adaptation and acclimation of tree species to shaded habitats we determined the growth, biomass partitioning and morphology of seedlings of nine near-boreal tree species in high- and low-light greenhouse environment (25 and 5% of full sunlight, respectively), comparable to sunlit gap and shaded microsites in boreal forests. The species differ widely in shade tolerance, seed size and leaf life span. 2. In low light, all species allocated proportionally more biomass to stems and less to roots, but the same to foliage, compared with the high-light environment. At a common size, all species had finer leaf morphology (higher specific leaf area, SLA) but coarser root morphology (lower specific root length, SRL) in low than high light. From a whole plant perspective, all species enhanced leaf area per unit plant mass (leaf area ratio, LAR) in low light and root length per unit plant mass (root length ratio, RLR) in high light. 3. Shade-intolerant deciduous species had higher RGR, SLA and SRL than larger seeded evergreens: ranking from Populus, Betula and Larix spp., then to five evergreen Pinus, Picea and Thuja spp., which were generally comparable in these traits. There were no changes in growth rankings of species between high- and low-light environments, nor consistent differences among species in biomass partitioning. Hence, species differences in leaf and root morphology (SLA, SRL) drove whole plant patterns, such as Populus, Betula and Larix had greater total leaf area and root length per unit plant mass (LAR and RLR, respectively) than the evergreens. Interspecific variation in RGR in both high and low light was positively correlated ( r  0·9) with SLA, SRL, LAR and RLR, and negatively correlated (r ‐0·9) to seed mass and leaf life span. 4. These data suggest that SLA, SRL, NAR and RGR are closely associated with variation in life-history traits and that variation in leaf and root structure more strongly influences patterns of RGR among species and light environments than does biomass partitioning.

Tomato Plant Culture In the Field, Greenhouse, and Home Garden

Abstract: Introduction.- Plant Characteristics and Physiology.- Fruit Characteristics.- Plant Nutrition.- Field Production in Soil.- Greenhouse Production.- Seed and Seedling Production.- Plant Disease and Insect Control.

Non‐photosynthetic mechanisms of growth reduction in pea (Pisum sativum L.) exposed to UV‐B radiation

Abstract: Pisum sativum cv. Guido grown under controlled environment conditions was exposed to either low or high UV-B radiation (2·2 or 9·9 kJ m–2 d–1 plant-weighted UV-B, respectively). Low or high UV-B was maintained throughout growth (LL and HH treatments, respectively) or plants were transferred between treatments when 22 d old (giving LH and HL treatments). High UV-B significantly reduced plant dry weight and significantly altered plant morphology. The growth and morphology of plants transferred from low to high UV-B were little affected, when compared with those of LL plants. By contrast, plants moved from high to low UV-B showed marked increases in growth when compared with HH plants. This contrast between HL and LH appeared to be related to the effect of UV-B on plant development. Exposure to high UV-B throughout development consistently reduced leaf areas. In fully expanded leaves there was no significant UV-B effect on cell area and reduced leaf area could be attributed to reduced cell number, suggesting effects on leaf primordia. Further reductions in the leaf area of younger leaves were the result of the slower development rate of plants grown at high UV-B, which also resulted in significant reductions in leaf number.

Plant Density Effects on Tropical Corn Forage Mass, Morphology, and Nutritive Value

Abstract: Tropical corn (Zea mays L.) has potential as a silage crop in double-crop systems with cool-season annual grasses in the southeastern USA. In a 3-yr study conducted in silt loam soils in southeast Louisiana, plots within stands of Pioneer hybrid X304C tropical corn planted at 89 000 plants ha -1 were thinned to achieve harvested plant densities of 44 830, 52 150, 58 130, 65 150, and 72 920, plants ha -1 to determine the effect of plant density on total forage mass, plant morphology, and forage nutritive value of tropical corn. Total forage mass was greater at higher plant densities than at lower plant densities, but forage mass was not different among plant populations that exceeded 58 130 plants ha -1 . Leaf concentration of dry matter did not differ among plant populations and averaged 300 g kg -1 . The sum of stem and grain concentrations was similar among treatments and ranged from 622 to 637 g kg -1 . Within the stem and grain components, grain concentration decreased and stem concentration increased in an almost one-to-one relationship as plant density increased. Forage nutritive value of tropical corn was similar among plant densities. In vitro true digestibility averaged 654 g kg -1 across all plant densities. Increasing forage mass, coupled with stable forage nutritive values, indicates that, until some factor limits production of high-quality tropical corn silage, high plant densities are desirable. Under the environmental conditions of this experiment, it appears that plant densities of about 58 000 plants ha -1 are optimal.

Variability in essential oil chemistry and plant morphology within a Leptospermum scoparium population

Abstract: Essential oil composition and plant morphology were observed over four years in individual plants raised from seed of a wild population of Leptospermum scoparium (Myrtaceae) collected at a single site in New Zealand. Principal component analyses of data from young and mature plants showed no significant grouping of plants on the basis of oil composition, but identified differences between the essential oil components contributing most to variation in oil composition in both young and mature plants. The dominant variables were six sesquiterpene components in young plants, and three monoterpenes and two sesquiterpenes in mature plants. Levels of these components differed significantly at the population level between young and mature plants and also within and between seasons. Levels of all these components varied markedly within and between individual plants at all sample times. The habit, leaf size and density, and stem and foliage colour also varied markedly between individual plants. The variati...

To Shape a Plant—The Cytoskeleton in Plant Morphogenesis

Abstract: How different tissue and organ morphologies are reproducibly achieved is among the oldest questions in the study of developmental biology. Because plant cells are constrained by their cell walls and cannot migrate, plant morphology is generated by coordinately regulating the directions in which

Alteration of plant morphology by control of profilin expression

Abstract: Plant growth habit is altered by causing either under-expression or over-expression of profilin in a plant cell Under-expression of profilin can be achieved by transforming a plant or plant cell with a gene expressing an antisense mRNA complementary to the mRNA transcribed by the coding sequence of a profilin gene and expressing the gene in the plant or plant cell such that the antisense mRNA inhibits the production of the profilin in the plant or plant cell Under-expression of profilins in plants can lead to such alterations in growth habit as a dwarf phenotype, a reduced root and root hair system, and delay in the onset of flowering Over-expression of profilin can be achieved by transforming a plant or plant cell with a gene capable of expressing a profilin in the plant or plant cell and causing the transformed gene to be expressed in the plant or plant cell Over-expression of profilin in a plant can lead to such alterations in growth habit as a tall phenotype, an expansion of the root and root hair system, expansion of leaf surface area and accelerating the onset of flowering

Agronomic and seed quality studies in pyrethrum Tanacetum cinerariaefolium Sch. Bip.

Abstract: At the time this research project was initiated, the Tasmanian pyrethrum industry was attempting to establish crops by sowing rather than by planting of 'splits' or seedling plugs. This thesis investigated plant density and sowing times required for maximum yield. Studies were also conducted to improve chances for successful crop establishment from seed. That work investigated environmental requirements for germination and aspects of seed quality and seed production. Previous studies have examined the influence of density on yield of pyrethrins, but none had been conducted in sown trials, in cool temperate environments, over a wide range of plant densities. Furthermore, the influence of plant density on components of yield had not been intensively investigated. This work identified that maximum yield was achieved in the first season at between 16 and 39 plants/m2 and at or above 16 plants/m2 in the second season following establishment. Yield was a function of dry flower yield rather than due to change in percentage of pyrethrins in the flowers. Higher flower yield was associated with greater above- ground dry matter production. The yield component which increased with plant density was number of flowering tillers/m 2 . Yield components decreasing with density included number of flowering tillers/plant, flowers/tiller and dry weight/flower. Other aspects of changing plant morphology and development with density investigated included, crop height, mean flower maturity and plant survival. The recommendation to industry was to aim for a plant population of above 16 and below 39 plants/m2 . Yields achieved in this work were unprecedented in the pyrethrum agronomy literature. No reported studies have examined the influence of time of sowing on pyrethrins yield. Field studies showed that sowings later than mid-November led to significant reductions in yield in the first flower harvest. Yield reductions were associated with decreased dry matter production/plant and flowering tillers/plant. Later sowings resulted in plants failing to flower or in significant reductions in the extent of flowering. Sowing earlier than mid-November resulted in no significant increases in yield. As pyrethrum crops have not been traditionally established by sowing, only scant information was available on requirements for germination, or seed quality. A field study and three laboratory trials investigated the influence of temperature and seed quality on germination and emergence. Results demonstrated that rate and final emergence varied significantly at different times of year. In general, the proportion of viable seed sown that emerged and survived was very low. Both rate of emergence and final emergence percentage were associated with temperature. Laboratory investigation of germination percentage, rate and uniformity of germination of a seed lot under a range of constant temperatures confirmed the previously reported findings relating to germination characteristics of this temperate species. Unexpected though was the high proportion of dead seed found at temperatures only several degrees higher than the temperature for optimal germination rate. Six seed lots were subsequently germinated at low, medium and high temperatures which provided some insight into the seed death phenomenon as well as documenting the range of behaviours from different seed lots. An explanation for differences in germination behaviour involving seed maturity was proposed for different seed lots and this was tested in a subsequent study. Finally, the effects of an 18 month storage period on the germination characteristics seed lots was investigated in a laboratory trial. There was little change in most germination parameters except for time to complete germination which increased in all seed lots after storage and uniformity of germination which decreased. Changes were assumed to be due to satisfaction of an after ripening requirement. Laboratory studies investigated the influence of seed mass on various germination and seedling development characteristics. Variation in seed mass within seed lots was identified but this had little impact on rate of germination or other germination parameters. However, a following, study revealed that heavier seedlings emerged from seeds that germinated earliest within seed lots. Furthermore, heavier seedlings demonstrated faster development than did lighter seedlings. Although seedling mass was found to be associated with rate of germination within seed lots, this factor failed • to explain significant differences in mean time to germinate between seed lots. It was subsequently recommended to industry that cleaning on a size or mass basis could improve seed quality. The influence of harvest date on seed quality and quantity were investigated. Results indicated that losses of larger achenes from the harvested flowers were occurring with lateness of harvest. Characteristics of the seed including mean seed mass, proportion of viable seed in the sample, germination percentage and rate of germination were found to vary considerably with harvest date. Data generated in this work were found to be consistent with the model which proposed that variability in germination parameters was due largely due to maturity of seed at harvest. A following study revealed that relative position on the capitulum also had a profound influence on germination parameters of the seed. The recommendation for industry emanating from the harvest date work was that flowers should be cut at a field capitulum moisture of 25%. Finally, variation in seed quality and quantity was evaluated both within and between capitula. This study revealed that small flower heads produced fewer and smaller seed than larger heads. Outer achenes, regardless of whether they came from large or small capitula were found to germinate more rapidly than inner achenes. Peripheral achenes weighed more than central achenes and gave rise to heavier seedlings. The methods and results in this study will serve as a valuable source of information for agronomists and plant breeders working on improvement of pyrethrum production. The investigations on seed quality and seed production provide a sound base for future efforts to improve seed quality and crop establishment. The findings presented provide the Tasmanian pyrethrum industry with critical information with respect to target plant densities, sowing times, seed quality and seed production. It is expected that implementation of findings from the study will prove to be pivotal in continued industry profitability and expansion.