First Growth Flush Research Articles

Grass Tetany in Cattle

This document is about grass tetany, sometimes called grass staggers or hypomagnesemia, that can be a serious problem in Florida with cattle grazing small grain or ryegrass pastures. The problem is usually confined to lactating cows. It is always associated with an imbalance in the mineral components of blood serum, especially reduced magnesium levels. In Florida, grass tetany is more severe when cattle are grazing young forage, particularly the first flush of growth during December and January. Once the forage becomes more mature, the likelihood of problems is reduced. Grass tetany is apt to appear under conditions of nutritional stress. Placing cattle on winter pasture directly after being on frosted or other low quality pasture may cause such a nutritional stress. First published in April 1997.

Apical dominance and apical control in multiple flushing of temperate woody species

In young plants of many woody species, the first flush of growth in the spring may be followed by one or more flushes of the terminal shoot if growing conditions are favorable. The occurrence of these additional flushes may significantly affect crown form and structure. Apical dominance (AD) and apical control (AC) are thought to be important control mechanisms in this developmental response. A two-phase AD – AC hypothesis for the factors controlling a subsequent flush is presented and evaluated on the basis of currently known studies. The first, very early phase of this additional flush consists of budbreak and the very beginning of outgrowth of the newly formed current buds on the first flushing shoot. There is evidence that this response often involves the release of AD, which is significantly influenced by the auxin:cytokinin ratio as well as by other signals including nutrients and water. This first phase is immediately followed by a second phase, which consists of subsequent bud outgrowth under the influence of apical control. Although definitive data for hormone involvement in this latter process is sparse, there is some evidence suggesting nutritional mechanisms linked to possible hormone activity. Stem-form defects, a common occurrence in multiple-flushing shoots, are analyzed via the AD – AC hypothesis with suggestions of possible means of abatement.

Relationship between seasonal cambial activity, development of xylem and phenology in Azadirachta indica growing in different forests of Gujarat State

Seasonal cycle of cambial activity was compared among the trees of Azadirachta indica growing in Moist Deciduous (MDF), Dry Deciduous (DDF) and Scrub land Forest (SF) of Gujarat State. Radial growth occurred in two growth flushes in MDF and DDF. Cambial cell divisions in MDF started in February and June resulting maximal radial growth in August-September when the rains were heavy and ceased in January and May during the drier part of the year. In DDF the first flush of growth commenced in January with maximal xylem development in April and ceased in May. The second flush of cambial activity began in June with the arrival of rains, reached peak in October and ceased in December. Cambium was active throughout the year in SF and attained its peak activity thrice i.e. in February, July and October. With complete maturation of leaves in November, the cell divisions were rather slow in MDF and SF whereas no divisions were encountered in DDF. Cambial rays exhibited large intercellular spaces during drier months in all the three fo- rests. Seasonal behavior of vascular cambium was discussed in relation to phenology and local climatic conditions.

100 A Comparison of Two Media on Growth of Deciduous Azalea Shoots In Vitro

Micropropagation is a useful technique to propagate species such as deciduous azaleas, which are difficult to root from cuttings. To develop a micropropagation protocol that would be effective with a wide range of species and cultivars of native azalea, two culture media, Woody Plant Medium (WPM) (Lloyd and McCown, 1980) and ER medium (Economou and Read, 1994) were evaluated for ability to support growth of 11 species and four cultivars of deciduous azalea. Shoot tips were obtained from the first flush of growth in the spring on plants growing in the greenhouse or field. Following disinfection, the terminal and basal ends were removed from each explant. The explants were placed in culture tubes containing either WPM or ER medium with 12 mg/L 2iP and solidified with agar. Cultures were transferred to fresh medium every 4 to 6 weeks. Initial evaluations were made in 1996, and the experiment was repeated in 1997. In 1998, six of the taxa were evaluated for a third year. For most of the taxa evaluated, growth was superior on ER medium. On WPM, many of the cultures browned and died. R. canescens, R. viscosum, R. prunifolium, and R. austrinum are examples of species that preferred ER medium. R. alabamense, R. arborescens, and `My Mary' performed similarly on either medium.

The influence of shading on growth and morphology in seedlings of Quercus robur L. and Fagus sylvatica L.

Growth and morphology in relation to shading was investigated in young seedlings of oak ( Quercus robur L.) and beech ( Fagus sylvatica L.). First-year growth in oak seedlings was compared with first-year growth in beech, a shade-tolerant species. In addition, second-year growth, as influenced by previous and current year light conditions, was investigated in seedlings of oak. The seedlings of oak and beech were grown in various light intensities in a climatic chamber. The photoperiod was 16 h and the day/night temperature 18/14°C. In the first year of growth, oak and beech seedlings were grown in photosynthetic photon flux densities (PPFD) of 0.7, 1.5, 3.0, 7.3, 14.5 and 23.1 mol m −2 day −1, corresponding to about 2, 4, 9, 21, 43 and 70% relative light under field conditions in southern Sweden. In the second year of growth, oak seedlings grown in a previous-year PPFD of 0.7 and 14.5 mol m −2 day −1 were transferred to a current-year PPFD of 0.7, 7.3 and 14.5 mol m −2 day −1. Dry mass of leaves, stem and root in the oak and beech seedlings increased with PPFD. In beech, more dry matter was allocated to the shoot than to the root, whereas the root was more favoured in oak. Unit leaf rate (ULR) increased with PPFD in both species. During the first year, oak showed a higher productivity per leaf area (ULR) than beech. ULR in oak was similar or higher during the second year compared with the first year. Dry mass of dark grown oak seedlings was about 50% of the seedling dry mass achieved at the lowest PPFD. During the second year, the first flush of growth in oak was affected by the previous-year PPFD, and the second flush by the current-year PPFD. First-year seedlings of oak and beech seem to be equally well adapted to low light conditions and it would thus be possible to regenerate oak as well as beech under a dense canopy. However, the present results indicate that oak seedlings may be sensitive to increasing competition for light, as simulated by a transfer to low light level in the second year. Therefore, light intensity should be increased after the first year of seedling growth in regeneration of oak.

The Influence of Shoot Growth on the Pattern of Axillary Development on the Long Shoots of Young Apple Trees (Malus domestica Borkh.)

The influence of shoot growth on the pattern of axillary development was investigated in apple (Malus domestica Borkh. cv. Braeburn) long shoots, either monopodial (all the metamers are produced by the same meristem) or sympodial (composed by a proximal inflorescence, the bourse, and a relay-axis, the bourse-shoot). All of the studied shoots were characterized by the formation of two growth flushes during the same year. The study first involved measuring primary growth components of individual metamers (leaf size and length of the internode below) in the year of shoot growth. Then, for each metamer, the type of related axillary structure was noted, either during the same year (anticipated axillary shoots) or during the next one after budbreak. In the latter case, five types of axillary structures were distinguished: vegetative axis, inflorescences from which fruit was set, inflorescences from which fruit was not set, aborted bud, and blind node. The first analysis compared the two growth flushes. It showed that the distribution of types of axillary structure in the first flush of growth differed considerably between monopodial and sympodial shoots in that monopodial shoots tended to have more inflorescence buds and anticipated laterals than sympodial shoots, which had more blind nodes. The distribution of types of axillary structure was rather similar in the second growth flushes of both monopodial and sympodial shoots. The second analysis substantiated the significant role of the parent metamer in determining the absence, if under a minimal size, or the presence of vegetative or generative branching. The third analysis showed a high dependence between the types of axillary structure of adjacent metamers along a given growth flush. This spatial analysis revealed the following order between types of axillary structure: blind node, vegetative bud, inflorescence bud that did not set fruit later in the season, and finally, inflorescence bud that set fruit. When proceeding from the proximal to the distal part of a growth flush, axillary structures were ranked as described above and then in the reverse sense. Since these axillary structures are known to correspond to various numbers of preformed appendages, these results suggested that the location of a metamer on a shoot strongly conditioned the axillary organogenetic activity. The shoot growth characteristics, notably the presence of successive growth flushes in the same annual increment, not only conditioned the location of vegetative side branches but also influenced the distribution of blind nodes and inflorescences.

Fishwaste Compost Effects on Rhododendron Growth and Nitrogen Leaching and Transformation

Availability and leachability of N in fishwaste compost should be considered before it is used as growing media for nursery stock. This study examined N availability and leaching, and transformation of organic N constituents in fishwaste compost (HGF) as well as the effect of the compost on growth of rhododendron (Rhododendron fortunei 'Scintillation'). With an initially high inorganic N concentration, the compost enhanced growth of rhododendron during its first flush of growth. Because of extensive N leaching, this beneficial effect was short-lived. Periodic additions of N fertilizer at 150 mg N kg -1 were required to improve growth of rhododendron. Approximately 45% of inorganic N present initially in the HGF was leached regardless of the proportions of HGF in the mixtures. With N uptake by the plants representing a small fraction of inorganic N added, the inorganic N lost not accounted for probably was lost by denitrification and/or ammonia volatilization. Most N fertilizer applied as NH 4 NO 3 to 100% bark was also leached. Concentrations of labile amino acids changed significantly in 4 mo, from 53.6% to <5% of total organic N in the HGF. Similar reduction also occurred for amino sugars. Even with such a magnitude of change in the two labile N fractions, there was no marked increase in inorganic N in the leachate 2 wk after transplanting and in growth of rhododendron. A large proportion of amino acids and amino sugars present in the compost initially were probably transformed to a more stabilized organic N form.

Vacuole proteins in parenchyma cells of secondary phloem and xylem of Dalbergia odorifera

Light- and electron-microscopic observations were made on the stem parenchyma cells of Dalbergia odorifera T. Chen (Papilionaceae), a tropical deciduous tree. In the secondary phloem of branchlet and trunk, all of the parenchyma cells except companion cells contain vacuole proteins. Only the outer secondary xylem of branchlets, but not trunk secondary xylem, has proteins in the ray parenchyma and the vasicentric parenchyma. The xylem vacuole proteins begin to accumulate at the end of the growing period and they disappear after the first flush of growth in spring. The vacuole proteins in phloem cells, particularly in the cells near the cambium, also show seasonal fluctuations. Under the electron microscope, the vacuole proteins appear as fibrous materials in aggregation or in more or less even dispersion, and they occur in the large central vacuoles during both the growth and dormant periods. According to the published studies, the stem storage proteins in the temperate trees appear as small protein-storage vacuoles or protein bodies, and the proteins in the tropical trees occur in large central vacuoles. This distinction is assumed to be related to the differences in the nature of dormancy between temperate and tropical trees.

Effects of Plant Growth Stage on Glyphosate Absorption and Transport in Ligustrum (Ligustrum japonicum) and Blue Pacific Juniper (Juniperus conferta)

Carbon-14-labeled glyphosate [N-(phosphonomethyl)glycine] was foliarly applied to ligustrum (Ligustrum japonicumThunb.) and blue pacific juniper (Juniperus confertaParl. ‘Blue Pacific’) at the following growth stages: cold acclimation, winter dormancy, budbreak, shoot elongation, and termination of the first flush of growth (shoot termination). At shoot elongation juniper plants absorbed 2% of applied14C by 14 days after treatment (DAT). Applications at other growth stages resulted in no significant absorption of14C by junipers. Within 7 DAT the amounts of radioactivity absorbed by ligustrum were significant and depended upon growth stage in the following order: budbreak &lt; shoot termination &lt; shoot elongation. Absorption by overwintered leaves occurred at budbreak but not at elongation or termination. Transport of absorbed14C in ligustrum was primarily acropetal and occurred only in budbreak and flowering treatments. Differences in tolerance to glyphosate between juniper and ligustrum appear to be related to differential absorption. Seasonal differences in ligustrum tolerance also appear to be associated with differences in absorption. Although growth stage affected transport in ligustrum, differential transport does not appear to play a major role in seasonal influences on long-term glyphosate phytotoxicity.

Modification of episodic growth in Skimmia japonica ‘Rubella’ by gibberellic acid treatment

Applications of GA 3 in May/June, when the first flush of growth was maturing, induced an extra flush of vegetative growth and initiated lateral bud break. Flower initiation was delayed and flower size reduced by the GA 3. These responses were only slightly modified by additional sprays with BAP and TIBA. GA 4+7 was ineffective in promoting either extra extension growth or lateral bud break, but it did reduce flower size.

The influence of grazing on the botanical composition of an irrigated pasture at Lawes, south-east Queensland

An irrigated mixed pasture of short rotation ryegrass (Lolium multiflorium x L. perenne) Phalaris tuberosa L. and white clover (Trifolium repens L.) was grazed at six- and eight-weekly intervals and at six-weekly intervals with two summer grazings omitted. Yields of the components were measured for three years. Short rotation ryegrass contributed very little to yield after its first flush of growth following sowing. At the end of the three years, short rotation ryegrass in the six-weekly grazing treatment was contributing six per cent of the total yield, two per cent in the eight-weekly treatment, and one per cent in the rested treatment. Resting for eighteen weeks in summer favoured the development of Phalaris and hence reduced clover dominance. At the end of three years, Phalaris was contributing forty-four per cent of the total yield in the rested treatment and twenty-three and thirty-seven per cent in the six-weekly and eight-weekly grazing treatments.

A SEASONAL STUDY OF THE VEGETATIVE SHOOT APEX AND THE PATTERN OF PITH DEVELOPMENT IN HIBISCUS SYRIACUS

Tolbert, Robert J. (West Virginia U., Morgantown.) A seasonal study of the vegetative shoot apex and the pattern of pith development in Hibiscus syriacus. Amer. Jour. Bot. 48(3): 249–255. Illus. 1961.—The shoot apex of Hibiscus syriacus L. is described as having a cytohistological zonation superimposed on a tunica‐corpus configuration. The apex is flat‐topped or may have a saddle‐back or concave appearance as seen in median longitudinal section. The metrameristem, consisting of the tunica and corpus initials, is comprised of large, light‐staining, vacuolate cells that have thick cell walls and exhibit much dark‐staining intercellular substance. Surrounding the metrameristem is the flanking meristem, which is responsible for the outer layers of the shoot, and from which the leaf primordia arise. The pith rib meristem lies below the metrameristem and consists of files of cells that are responsible for the pith. There are no major seasonal changes in the structure of the apex during the yearly cycle. The pith displays a long‐shoot type of development with the cells remaining in distinct files during the first flush of growth in the spring. As growth slows and internode elongation is gradually reduced, the pith displays the characteristic short‐shoot type of development, consisting of a spongy tissue of rounded cells with many intercellular spaces and no distinct files of cells. A crown is differentiated across the top of the pith at the end of the growth period. This consists of a band of cells with thick, dark‐staining cell walls, which separates by the apex from the last year's growth. In contrast to many gymnosperms, this crown is dispersed by renewed cell activity the following spring.

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