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... Nitrogen (N) is the number one limiting nutrient for plants, and especially so for perennial grasses which require continual access to small amounts of N throughout the season in order to maintain growth (Lynch et al. 2004). Nitrogen demand of perennial pastures typically follows the growth curve for cool-season grasses, where the demand for N peaks during spring growth but slows down during midsummer along with growth due to stress from higher than optimum temperatures (Wolf et al. 1979). As temperatures cool in late summer to early fall, growth resumes due to reduced stress, and demand for N increases although not as high as with spring growth. ...
This study was conducted to determine the effect of composted dairy manure (CDM) addition on nitrogen (N) mineralization in perennial forage production system undergoing transition to organic management. A field experiment was carried out on a Gray Luvisol of northeastern Colorado (40°39′N, 104°59′W) in 2008 and 2009, using the in situ resin core method. CDM was top-dressed onto two mixtures of perennial grasses at 22.4 and 11.2 Mg ha−1 in 2008 and 2009, respectively. Additionally, a control with no CDM addition was included. In 2008, N mineralization was unchanged following the addition of CDM compared to unamended control, irrespective of grass mixture. In 2009, N mineralization was greater in CDM-amended plots than controls, but these differences were only marginally significant (P < 0.1). There were, in general, no significant total dry matter (DM) yield or N uptake differences between grass mixes that received CDM and those that did not regardless of year, but generally total DM yield declined in 2009 compared to 2008. No significant differences in N mineralization, total DM yield or N uptake between controls and CDM-amended soils suggests that CDM-derived N mineralization rates were considerably lower than expected and thus may not keep up with N demand of perennial forage grasses in the short term, as evidenced by low total DM yield in 2009. Thus, we suggest that high application rates of CDM, in addition to quality, may be needed for at least 3 years until a reserve of organic N pool that will mineralize over time is built, particularly for a soil in transition to organic management.
... O maior número de perfilhos produzido pelas plantas podadas em relação às não podadas ratifica a hipótese do controle hormonal de desenvolvimento de gemas laterais pelo meristema apical, sendo a auxina o principal hormônio envolvido nesse processo, representado possivelmente, pelo ácido indolacético, sintetizado na região apical e transportado para os meristemas laterais (AWAD; CASTRO, 1983). A dominância apical se manifesta por inibição do crescimento das gemas axilares ou laterais, sendo os meristemas apicais e folhas jovens os principais sítios de síntese de auxinas na parte aérea da planta, ocorrendo uma ação indireta na dominância de gemas e brotos (PHILLIPS, 1969). ...
Brazil is the second world producer of banana, however, the expansion of the banana crop has many difficulties, as the lack of suckers in amount and quality, necessary for implantation of new banana plantations. The objective of this research work was to evaluate the influence of the pseudostem pruning with elimination of the apical meristem of the rhizome and of doses of nitrogen and boron on the production and growth of banana suckers. The experiment was carried out at Centro de Formação de Tecnólogos - UFPB, state of Paraíba. The experimental design was randomized blocks, with four blocks and nine mother plants by experimental unit, being two useful plants. The evaluated factors were doses of N (0 to 240 g plant⁻¹) and of B (0 to 2,2 g plant⁻¹) combined by the use of the experimental matrix ‘Central Composite’, originating nine treatments, applied with pruning and without pruning of the mother plant pseudostem. The data were submitted to the variance analysis and regression. In the plants with pruning, it was reduced the sucker number, which presented smaller growth, on the other hand, it increased the concentration of total chlorophyll. For the production of 'Pacovan' banana suckers, it is recommended the pruning of the mother plant pseudostem with elimination of the rhizome apical meristem and the application of N.
... O maior número de perfilhos produzido pelas plantas podadas em relação às não podadas ratifica a hipótese do controle hormonal de desenvolvimento de gemas laterais pelo meristema apical, sendo a auxina o principal hormônio envolvido nesse processo, representado possivelmente, pelo ácido indolacético, sintetizado na região apical e transportado para os meristemas laterais (AWAD; CASTRO, 1983). A dominância apical se manifesta por inibição do crescimento das gemas axilares ou laterais, sendo os meristemas apicais e folhas jovens os principais sítios de síntese de auxinas na parte aérea da planta, ocorrendo uma ação indireta na dominância de gemas e brotos (PHILLIPS, 1969). ...
Brazil is the second world producer of banana, however, the expansion of the banana crop has many difficulties, as the lack of suckers in amount and quality, necessary for implantation of new banana plantations. The objective of this research work was to evaluate the influence of the pseudostem pruning with elimination of the apical meristem of the rhizome and of doses of nitrogen and boron on the production and growth of banana suckers. The experiment was carried out at Centro de Formação de Tecnólogos-UFPB, state of Paraíba. The experimental design was randomized blocks, with four blocks and nine mother plants by experimental unit, being two useful plants. The evaluated factors were doses of N (0 to 240 g plant-1) and of B (0 to 2, 2 g plant-1) combined by the use of the experimental matrix 'Central Composite', originating nine treatments, applied with pruning and without pruning of the mother plant pseudostem. The data were submitted to the analysis of variance and regression. In the plants with pruning, it was reduced the sucker number, which presented smaller growth, on the other hand, it increased the concentration of total chlorophyll. For the production of 'Pacovan' banana suckers, it is recommended the pruning of the mother plant pseudostem with elimination of the rhizome apical meristem and the application of N.
... That study showed that low N overcomes effects on apical dominance: when N content was high, Linum developed lateral buds extensively, but when N content was low, their outgrowth was nil and could not be induced with high light. Indeed, Phillips (67) revealed that N concentration was higher on a dry-weight basis in P isum buds whose lateral buds were inhibited than in buds released from apical dominance. ...
None of the physiological events in plant growth and development is truly independent. Photosynthesis, flowering, and mineral transport are sharply focused areas of research; yet these phenomena are not separable from other metabolic events in the plant. This feature of interdependence may be called correlations (26) or growth correlations (49, 50). The control exerted by the growth zone emanates from a meristem; these meristems include the root or shoot apex, cambium, flowers, fruit, pollen on stigma, and the ovule or seed in a fruit.
Lebendige Systeme müssen als in beständiger Entwicklung befindliche Systeme aufgefaßt werden. Diese Feststellung gilt für die Einzelzelle genauso wie für das vielzellige System. Wenn man einen Organismus kennzeichnen will, muß man seine gesamte Ontogenie ins Auge fassen, nicht nur bestimmte Ausschnitte aus dieser Ontogenie. Eine Ontogenie kann einfach sein, wie zum Beispiel die vegetative Ontogenie der einzelligen Grünalge Chlorella vulgaris (Abb. 65) oder kompliziert, wie zum Beispiel die durch einen Generationswechsel ausgezeichnete Ontogenie einer angiospermen Blütenpflanze (Abb. 66). Bei der wissenschaftlichen Behandlung eines Organismus müssen wir stets im Auge behalten, daß sich lebendige Systeme in beständiger Entwicklung befinden. Jede statische Betrachtungsweise ist deshalb unangemessen. Es ist bedauerlich, daß diese statische Betrachtung in vielen morphologischen Lehrbüchern vorherrscht.
Abb. 65
Die Ontogenie der einzelligen Grünalge Chlorella vulgaris. Bei der vegetativen Fortpflanzung werden innerhalb der Zellwand der Mutterzelle Autosporen gebildet. Diese wachsen nach der Freisetzung zur Größe der Mutterzelle heran. Alle Zellteilungen, die bei dieser Ontogenie vorkommen, sind Mitosen. Sexualität, d. h. Meiosis und Befruchtung, hat man bei Chlorella nie beobachtet. (In Anlehnung an Oltmanns, 1922)
Hormones are chemical messengers which act at target sites to regulate rates and amounts of growth of cells in tissues of roots, stems, leaves, buds, flowers, and fruits. In this chapter, we shall focus on the roles that hormones play in the orientation of growth of plant organs, particularly of roots and shoots. The basic growth-orienting processes that we shall discuss include phototropism—the orientation of shoots toward unilateral light sources; gravitropism—the orientation of roots downwards and of shoots upwards in response to gravistimulation (placement of plants horizontally); and thigmotropism—the change in orientation of growth in stems from one of rapid elongation to one of repressed elongation and promoted lateral expansion as a result of mechanical perturbation.
We retrospectively evaluate the impact of the various mergers of the local exchange companies in the United States telecommunications industry between 1988 and 2001 on technology investment levels. We use treatment effects modelling to evaluate major mergers in a sector where technology diffusion is important, and the approach accounts for selection bias and the endogenous nature of mergers. Our framework is based on behavioral theories of the firms and we use co-evolutionary and dynamic capabilities approaches in framing our analyses and explaining our results. We find that across firms and time, the merger events are positively and significantly associated with investments in fiber and digital assets. We stratify the data by size of firm to undertake detailed data analysis because of the presence of firm-specific heterogeneities and find that for the smaller merging firms there is a negative and significant association of mergers with investments in fiber and digital assets while for the larger merging firms this mergers and fiber and digital assets investments association is positive and significant. Our results support the predictions of the behavioral theories of the firm, and particularly the dynamic capabilities perspective. We draw implications for theory and competition policy of our results.
A procedure for the regeneration of fertile plants by organogenesis from tissue cultures of soybeans, Glycine max is described. Seeds were germinated on reduced inorganic salt MS medium containing 5μM BA. Cotyledonary nodes were excised and cultured on the same medium. Presence of BA in the medium during seed germination and culture of nodal explants was required for multiple shoot and shoot-bud formation. Histological analyses established the de novo nature of shoot regeneration. Separate reduction of the concentration of inorganic salts or substitution of sucrose for fructose during culture had minimal effects on the regeneration response. Conversely, if the BA was reduced, the inhibition response could not be overcome by increased salt concentration or altered carbon source.
1. The physiological characteristics of satsuma mandarin trees having flowers with or without leaves make an interesting object for study.
2. Six 15-year-old satsuma mandarin trees growing at Fujieda in the citrus region of Shizuoka, were selected for their uniformity in size and other general conditions.
3. It might be assumed that the production of flowers is a reaction to the supply of elaborated food material in the tree and that the tree responds by putting forth leafy and/or leafless flowers, corresponding to the vigour of vegetative growth.
4. The figures given in Table 1 show the percentage distribution of fruit branches according to length, diameter at the base and volume.
A survey of this Table shows longer and larger branches present on oblique and vertical framework branches.
There is evidently a tendency for the vertical framework branches to produce stronger fruit branches.
5. The figures given in Table 2 show flower production on fruit branches of different lengths for vertical, oblique and horizontal framework branches.
In order to place the number of flowers produced on the fruit branches of different lengths on a comparable basis, the results are expressed per 10cm length or per 1cm³ volume of each fruit branch.
Many more flowers are produced on short fruit branches growing from horizontal framework branches.
There is evidently a tendency for fruit branches of poor growth to produce far more flowers per 10cm length and per 1cm³ volume.
6. The figures given in Table 3 show that both leafy and leafless flowers are produced most profusely on short fruit branches present on the horizontal framework branches, and this is particularly true of leafless flowers.
7. The figures given in Table 4 show that the leafless type is produced more abundantly on fruit branches present on the horizontal framework branches and less on fruit branches present on the vertical framework branches.
The leafy type is produced more abundantly on fruit branches present on the vertical framework branches, the opposite of the situation for the leafless type.
8. It is shown in Table 6 and Fig. 6 that the development of the leafless flowers is inferior to that of the leafy flowers in size and weight. The leafless flowers, present on fruit branches of poor growth, are inferior in the nutritional competition and tend to cease growth and abscise earlier in the season.
