Showing papers on "Shoot published in 1975"

Comparison of the effects of a localised supply of phosphate, nitrate, ammonium and potassium on the growth of the seminal root system, and the shoot, in barley

Abstract: SUMMARY Barley plants were grown for 21 days in sand culture, continuously irrigated with nutrient solution. The rooting depth was divided into three compartments, one above another, such that different zones of the root system could be supplied with very low or high concentrations of a single inorganic nutrient, all other nutrients being maintained at a high concentration. Exposure of parts of the main seminal roots (axes) to high concentrations of phosphate caused a localized promotion of the initiation and subsequent extension of both first and second order laterals, compared with zones receiving very low concentrations of phosphate. This resulted in considerable modification to root form, but with only a small depression in shoot growth, compared with control plants receiving an ample supply to all parts of the root system. The extension of seminal axes was little affected by the concentration of phosphate to which they were exposed. Similar responses to those described for phosphate occurred with variation in concentration of nitrate or ammonium, but with potassium a localized supply promoted the growth of laterals to approximately the same extent as controls throughout the entire root system. The experiments show that adequate external concentrations of nitrogen and phosphorus are required by any part of the root system for optimal growth of laterals, but not axes. Possible mechanisms which compensate shoot growth when nutrients are supplied to only part of the root system, and agronomic implications, are discussed.

Experimental ecological genetics in plantago

Abstract: SUMMARY Induction of roots and shoots from leaves of Plantago lanceolata L. using IAA is a very effective technique which could be extended to large scale cloning for vegetative propagation and assay procedures in genecological studies on this and other species. In P. lanceolata, there were no differences between populations from contrasting habitats with regard to proportion of leaves producing roots and shoots. There was a high correlation between zinc tolerance measured on rooted leaves and on equivalent rooted tillers.

The possibility of predicting solute uptake and plant growth response from independently measured soil and plant characteristics

Abstract: A model of the way the rate of growth of a plant may be affected by the level of supply of a nutrient is presented. Growth rate is linked to the nutrient level of the photosynthetic tissues, which is assumed to control changes in the net assimilation rate, the leaf area per unit shoot weight, the shoot: root ratio, the root surface area, and the distribution of nutrient between root and shoot. The uptake of nutrient depends on the concentration of nutrient at the root surface, the root surface area and its absorbing power. All these relationships may be determined in stirred solution culture. A method of applying this information to soil grown plants is suggested.

Movement of ethylene from roots to shoots, a factor in the responses of tomato plants to waterlogged soil conditions

Abstract: SUMMARY Epinastic growth by petioles of tomato (Lycopersicon esculentum Mill., cv. Moneymaker) is stimulated by waterlogging the soil and the responding leaves and other shoot parts contain higher concentrations of ethylene than those of non-waterlogged plants. Waterlogged soil also contains increased amounts of ethylene in solution and the possibility that ethylene from this source can move to the shoots of waterlogged plants has been tested by applying the gas to the roots of plants growing in water culture. When concentrations of 2 ppm and above are supplied in this way, petiole epinasty develops in association with increases in ethylene extracted from the responding petioles. When 100 ppm is applied to the roots, increases in ethylene in the petioles precede the development of epinastic growth. Use of [14C] labelled ethylene indicates that the gas can move rapidly, unchanged from roots to shoots. The movement of ethylene and epinastic growth are both reduced if plants are previously steam-girdled near the base of the stem, suggesting that much ethylene moves by a route other than the transpiration stream. Ethylene supplied to the roots is shown to promote adventitious rooting and downward rolling of the young leaf laminae and to modify the orientation of shoot growth in the tomato mutant‘diageotropica’. It is proposed that increases in soil ethylene and movement of the gas to the shoot system are factors contributing to the development of epinasty and other responses of the shoots to waterlogging the soil.

Studies of flowering behaviour in Eucalyptus regnans F. Muell.

Abstract: The buds of Eucalyptus regnans are protected by an operculine involucre for 12 months and develop as exposed umbels for a further 15-17 months. The flowering period is about 3 months but the extreme range is from late February to early July at elevations of 600-750 m. Flowers remain open for 1-2 weeks. Older trees tend to flower later than younger trees on the same site. Pollination is probably effected chiefly by insects and birds. Flowering abundance follows a 2-year cycle with a tendency for heavier production every fourth year, but this pattern may be interrupted by severe insect attack on young shoots. Considerable losses occur at all stages of development owing to abscission, and to damage by gall and other insects. Quantitative estimates of flowering from litter trays indicate that the flower production of good years may be 25-65 times as great as in poor years. The mature forest produced 2.15-15.5 times as many flowers as the pole stage trees, and 1.5-10 times as many as the spar stage forest. Estimates of the fruit set following the late autumn flowering of 1954 indicate that that of the mature forest was 1.6 times as great as that in the spar stage forest and 3.5 times as great as that in the pole stage forest. The corresponding relative flower abundance in these forests was 1.5 and 3.8 respectively. However, the percentage of Rowers setting fruit from the early autumn flowering of 1956 was very much lower. Most capsules abscind or dehisce or fall attached to twigs within 3 years of their maturity. The quantitative estimate of flowering and fruit set permits seed crops from heavy flowering to be forecast a few years ahead of seed fall.

Flower Development of the Chinese Gooseberry (Actinidia chinensisPlanch.): I. Development of the Flowering Shoot*

Abstract: Flower development of the Chinese gooseberry (Actinidia chinensis Planch.) was followed for the 1971–72 growing season for the pistillate cultivar ‘Hayward’ and the staminate clone ‘Alpha’. Flower initiation takes place late in the seasonal cycle, occurring just before the resumption of shoot growth in the spring (mid-late September). Development of pistillate and staminate flower buds is similar up to inception of the gynoe-cium which appears within 15 days of initiation. Pistillate flower buds continue androecial development but lack functional pollen, whereas staminate flower buds cease gynoecial development soon after the initiation of the stigma. Lateral flower buds are initiated giving a compound dichasium. In some pistillate cultivars, especially ‘Haywardrs, many of these lateral flower buds cease development soon after their initiation and abscise. Aberrant flower development occurs in some axils, notably in ‘Hayward’. The number of functional flowers remaining per shoot is independent of...

Study of callus growth and organ formation in wheat (Triticum aestivum) tissue cultures

Abstract: Callus cultures of wheat (Triticum aestivum L.) were established by incubation of segments from root tips, shoots of seedlings, and from rachis with B5 and T media. 2,4,5-Tri-chlorophenoxyacetic acid, Benazolin, and Banvel D (Dicamba) were found to be appropriate growth regulators for initiation and maintenance of wheat callus cultures. Cytokinins inhibited callus growth. This effect was less pronounced with zeatin than with kinetin and benzyladenine. Supplementation of media with cytokinins, however, increased the number of roots formed in the callus. Shoots and complete plants were regenerated from rachis and shoot callus.

Seasonal Shoot Growth of Eucalyptus spp. In the Brisbane Area of Queensland (With Notes on Shoot Growth and Litter Fall in Other Areas of Australia)

Abstract: Field data, collected at fortnightly intervals over a period of three years, show a distinctly bimodal rhythm in the shoot growth of Eucalyptus species in the Brisbane area of Queensland. Maximum growth occurs in autumn and spring growth is reduced during summer and, apart from periods of warmer weather, virtually ceases during winter. The bimodal growth rhythm is due to the interacting influence of unimodal curves relating monthly values for dry matter production of the leaf canopy to the respective effects of mean daily temperature, intensity of solar radiation, and available water. When the mean monthly temperature falls below 16-18°C, most photosynthates are translocated to stems and roots: little canopy growth then occurs, thus accentuating the winter depression in shoot growth. Shoot growth in the Brisbane region is compared with that observed in other areas of Australia. Shoot growth is minimal in plant communities dominated by: (a) arid to subhumid species of Acacia when the mean monthly temperature falls below 24-26°C (b) Eucalyptus spp., Myoporum sp., Heterodendrum sp. and dominant heath species when the mean monthly temperature falls below 16-18° (c) Acmena smithii (at least at Wilson’s Promontory) and Leptospermum myrsinoides when the temperature falls below 13-14° (d) Pinus radiata when the temperature falls below 10°. In contrast, Nothofagus cunninghamii shows little shoot growth when the temperature rises above 16°.

Endogenous shoot growth rhythms and indeterminate shoot growth in oak

Abstract: Wide variations of shoot growth patterns in saplings of pin oak (Quercus palustris Muenchh.) have been observed as a consequence of varying environmental conditions, experimental manipulations, and vigor of trees. Shoot growth patterns range from a series of recurrent, determinate flushes, constituting a genuine endogenous rhythm, to continuous, indeterminate growth. Observed growth patterns agree well with those predicted by a model of rhythmic growth which assumes the dependence of shoot growth on the functional equilibrium between shoot and root system. Indirect evidence suggests that cessation of shoot growth under favorable environmental conditions might be a consequence of internal water deficits. Observed differences in shoot growth patterns between young and mature trees are discussed as logical consequences of the model.

Effect of osmotic stress on abscisic acid levels in xylem sap of sunflower (Helianthus annuus L.).

Abstract: Addition of an osmoticum (-12 bars) to the rooting medium of sunflowers (Helianthus annuus L.) caused an increase in the level of abscisic acid (ABA) present in xylem exudate subsequently collected from cut shoots. Using tall and dwarf plants it was shown that there was a time lag in the appearance of increased levels of ABA in tall plants when compared with dwarf plants. The results indicate that the leaves, rather than the roots are the site of synthesis of ABA present in the xylem sap of osmotically stressed sunflower plants.

Influence of N‐Deficiency on the Abscisic Acid Content of Sunflower Plants

Abstract: Sunflower plants (7 weeks old) were transferred from a modified Hoagland solution to a N-free nutrient medium and kept there for 7 days. Abscisic acid (ABA) was determined in several parts of the plants and in exudates collected from the roots of some of these plants. N-deficiency considerably increased the ABA content of the leaves, especially the older ones, and also considerably increased the ABA content of the upper parts of the stem when compared to the control plants. In the roots and the exudates of these plants no ABA could be detected. After dissecting the stems the ABA content in the roots of the control plants with normal N supply dropped quickly, probably due to rapid metabolization. Judging by results obtained, it seems unlikely that the roots are responsible for the remarkable increase of the ABA content in the shoots caused by N-deficiency.

The Seasonal Growth of Eucalyptus regnans F. Muell

Abstract: At Wallaby Creek, Vic. (altitude 670 m), Eucalyptus regnans seedlings 1-6 m in height usually commence growth in early September, reach maximum growth in midsummer and cease growing in late May. The active growing season when shoot growth exceeds 12 mm per month is 7-9½. months. Slow growth occurs in midwinter in Melbourne (altitude 47 m) and is not affected by day length. The growth rates of seedlings of associated understorey species are, in descending order of magnitude: Acacia dealbata, E. vegnans, Prostantheva lasianthos, Pomadevvis aspeva, Acacia melanoxylon. Their growth periods are similar, except for that of A. melanoxylon which is much shorter. Leaves of E. regnans mature in 2½-3½ months. In larger seedlings some of the leaves produced are initiated during the growing season. The size of the mature leaf depends partly on the season of its emergence. In winter and spring, die-back of apical shoots occurs in most seedlings owing to weevil attack and fungal infection. Insects may severely damage young leaves, but rapid recovery in full light takes place by the development of axillary and accessory buds. Maximum diameter growth rates tend to occur in November just prior to the main peak of shoot extension. Further increases in diameter may occur in April, and slight shrinkage may take place in late summer and midwinter. The period of active growth can be correlated with the period over which the air temperatures at 1.3 m above ground exceed a daily mean of 5.0-7.5°C, a daily maximum of 12.8° and a weekly maximum exceeding 15.5°. Growth,resumption may be delayed until weekly minimum air tempera- tures rise above - 2°. The mean temperatures at 1.3 m are roughly the mean of air temperatures from the top and base of the shoot. The mean temperatures at the mean commencement and cessation of growth differ by only 0.6-1.6°C, whereas the day length differs by 1½ hr. Growth rates correlate strongly with mean temperatures (particularly mean maximum tempera- tures) in spring and early summer. The wide deviations which occur in late summer and early autumn may be attributable to depletion of soil water reserves.

Wheat Growth Related to Rhizosphere Temperature and Oxygen Levels1

Abstract: Although extensive research has been conducted on the separate effects of various soil-temperature levels and various soil-oxygen levels on wheat growth, little work has been done on the interaction of soil-temperature and soil-oxygen levels upon wheat response. Mexican semi-dwarf wheat (Triticum aestivum L. em Thell cv Yecora) was grown in soil at regulated temperatures under greenhouse conditions to measure response to varying combinations of root zone oxygen levels and soil temperatures. Components of dry weight production, tillering, leaf area, stomatal aperature, and leaf xylem tension were measured. Decreasing soil-oxygen levels reduced total, root, and top dry weight components and root/shoot ratios, reduced leaf area, and retarded tillering. Soil temperature of 15 C generally favored higher total, shoot, and root dry weight, and a lower root/shoot ratio, increased leaf area, and increased the number of tillers per plant at harvest compared to 9 and 21 C. Stomatal closure (as measured by a diffusion porometer) occurred at very low soil-oxygen levels, but no consistent aeration or temperature effect on leaf water potential was observed. Low soil temperature and low soil oxygen levels interacted to retard shoot development pointing to a dependence of shoot development on root metabolism. The data underscore the need to characterize both soil temperature and soil oxygen availability when considering either parameter separately in order to fully understand the relative oxygen status of plant roots.

Shoot formation in potato tuber discs in tissue culture

Abstract: Tuber discs of potato (Solanum tuberosum) growing on a modified Murashige and Skoog medium produced callus and embryoid bodies but failed to form shoots. However, if 0.4 ppm of 6-benzylaminopurine was added to the basal medium, shoots became visible seven weeks after inoculation.

The effects of ethylene in the root environment upon the development of barley

Abstract: Following observations that ethylene can occur in anaerobic or partially anaerobic soils at concentrations which can affect plant growth, shoot and root growth of barley plants, maintained in solution culture, were examined after long-term exposure of the roots to ethylene in air; the subsequent growth on transfer to a similar but ethylene-free environment was also studied. Both root and shoot dry weights were reduced slightly by the ethylene treatment; seminal root extension was inhibited greatly while lateral root growth was stimulated; absorption of ions and their transport from root to shoot within the plant was not affected. On transfer to an ethylene free environment the extension rate of the seminal axes increased markedly and was the greater the shorter the period of the preceding ethylene treatment; the extension of laterals initiated during the ethylene treatment was stimulated greatly but the growth of those formed subsequently was inhibited.

In vitro organ culture of Actinidia chinensis PL as a technique for vegetative multiplication

Abstract: SummaryFormation of shoot buds, roots and globular embryoids were induced in in vitro culture of stem and root segments of Actinidia chinensis PL (Kiwi or Ichang). Among several growth substances tested, zeatin, a natural cytokinin, was found to be most effective for the differentiation of shoot buds. Complete plants were obtained by isolating developed shoot buds from expiants and inducing root formation on them using a medium containing a low concentration of auxin.

Effect of aeration on the flood-induced formation of adventitious roots and other changes in sunflower (Helianthus annuus L.)

Abstract: The effects of flooding, flooding with aeration, and no flooding of the root system on shoot growth was studied in sunflower plants. The responses of shoots appear to be brought about by: (1) The anaerobic condition of the roots which causes stem dwarfing, chlorosis, and petiolar epinasty. (2) The presence of water in excess of field capacity (but not anoxia) around the roots which results in an increase in stem hypertrophy and the formation and growth of adventitious roots.

Influence of ultraviolet radiation on germination and early seedling growth

Abstract: The influence of UV-B radiation (280–320 nm) from filtered and unfiltered FS-40 fluorescent sunlamps on germination and early seedling growth was examined for a range of vegetables (tomato, radish, cucumber, lettuce, and bean) and field crops (wheat, cotton, soybean, and millet). Continuous exposure of seeds for 3 days to 26.9 × 10−2 W × m−2 UV-B radiation (280–320 nm) at 25°C, had a slight effect on fresh weight of seedlings but no appreciable influence on germination percentage, or dry weight of seedlings. Extending the time of exposure to 6 days, however, resulted in abnormal seedling growth in all species but wheat. Typical responses were short, stubby roots, bronzing of the cotyledons, increased pigmentation, and abnormal curvature of the shoots.

The effect of soaking and drying seeds before planting on the germination and growth of Triticum vulgare under normal and saline conditions

Abstract: The soaking of wheat seed (Triticum vulgare L.) in water or CaCl2 solutions followed by air-drying before planting accelerated the germination but did not affect the final percentage germination and subsequent growth of the seedlings under normal conditions. However, under conditions of 0.5% NaCl salinity the soaking and drying of the seeds before planting stimulated the germination and growth of the seedlings. In no case were the presowing treatments more effective in improving the germination and root and shoot growth under 0.5% NaCl salinity than under normal condition. Under 0.5% NaCl salinity the seedlings grown from treated seeds had more extensive and deeper root systems than the seedlings grown from untreated seeds. Presowing soaking of the seed failed to improve the germination under increasing salinity of 1.0 and 1.5% NaCl.

The life history of shoots of Carex lacustris

Abstract: Most shoots of Carex lacustris live for about 12–14 months, emerging in autumn, overwintering as shoots of up to 50 cm in length, and maturing during the next summer. Others emerge in early spring but both groups die in late autumn. A third class emerges in late July or August, grow to be over 50 cm in length, and die in late autumn, living only 2 or 3 months.Flower initials in this species begin growth in the September–October period and overwinter while about 1.0 cm in length. The shoots that develop inflorescences are in general longer, heavier, and have a greater basal diameter than those shoots which do not flower. More shoots flower if the water level in the marsh was high the previous year.

Effect of Root Temperature on Budbreak, Shoot Growth, and Fruit-Set of 'Cabernet Sauvignon' Grapevines

Abstract: Three-year-old dormant 9Cabernet Sauvignon9 vines, growing in 5-gallon containers in a greenhouse, were pruned to two 10-node canes and then grown for 9 weeks in water baths With root temperatures kept at 11, 15, 20, 25, 30, and 35 C. Air temperatures were the same for all treatments, fluctuating between a minimum of 20 C at night and a maximum of 32 C in the day. Budbreak and bloom occurred 3 to 8 days earlier at 25-30 C than at 11 C. The number of buds that broke per vine increased with temperature, and was 2 to 3 times as great at 30-35 C as at 11-15 C. Total shoot growth per vine, measured as length or dry weight, was maximal at 30 C root temperature, as was also the total number of leaves and leaf area per vine. Average shoot length, dry weight per unit length of stem, leaf area, and leaf and cluster dry weights were significantly less at 35 C than at lower root temperatures. With an increase in temperature between 15 and 35 C, there was a decrease in percent dry matter in stems but an increase in leaves. The number of cluster per vine was proportional to the number of buds that broke. The number of berries set per vine did not differ significantly with temperature. However, the number of berries per cluster was significantly greater at 11 C than at root temperatures of 20 C or higher, with berry set approximately proportional to leaf area per cluster.

The question of grain content and forage quality in maize: comparisons between isogenic fertile and sterile plants

Abstract: Results are presented from four experiments in which comparisons were made between isogenic sterile and fertile plants of maize to study the effects of grain content on yield and quality of shoot dry matter. In two experiments comparisons were made over a range of densities, extending from 5 to 25 plants/m2 in 1972 and 5 to 20 plants/m2 in 1973. The other two experiments, grown in 1974 at a density of 10 plants/m2, were sampled 30, 60 and 90 days after flowering.In 1972 and 1973 yield of shoot dry material was about 10% higher in fertile plants at the lowest density, 5 plants/m2, but grain formation had a negligible effect at higher densities. In 1974, at 10 plants/m2, the yield advantage for fertile plants was 6–7%. These results are in line with other European data, but show a much smaller effect of grain formation on shoot dry matter yield than is normally recorded in USA trials. The discrepancies probably reflect differences in environmental conditions.Absence of grain had little effect on contents of nitrogen, ash and in vitro digestible dry matter, and increased content of pepsin soluble material and hot water soluble carbohydrates. Percentage content of dry matter in the shoot was higher in fertile plants in 1973, and during the later stages of crop development in 1974.The results suggest that the importance attached to high grain content as an essential requirement for yield and quality in forage maize is exaggerated, and that the restriction of maize breeding and testing programmes to assessments of grain production, in the belief that the best grain varieties will also be best for forage, can no longer be justified in northern European countries.

Temperature and Other Climatic Influences on Shoot Development and Growth of Eucalyptus regnans

Abstract: The growth and development of shoots of Eucalyptus regnans F. Muell. trees up to 8 m tall growing in their natural environment in central Tasmania were studied continuously for 3 years and related to climatic factors. The influences of temperature were further investigated by experiments with seedlings in a phytotron. Height growth was practically nil in winter and greatest in summer. Throughout the year weekly rates of height growth were closely related to weekly mean maximum air temperatures, increasing from nil or slight at 10°C to peak rates at the highest temperatures experienced (25°). Substantial diameter increments were observed in all seasons and their relation to temperature was relatively weak. There was no positive relation between weekly growth in height or diameter and weekly precipitation. Bud and shoot growth were characterized by continuity of development of all organs throughout the growing season. The youngest of the leaves and internodes which had emerged before winter from the bud resumed growth in spring, but did not reach the lengths achieved by those leaves and internodes which emerged from the bud after winter. It was only by this morphological feature that the boundaries of the annual shoot were identifiable. In agreement with the field observations, the growth of seedlings in glasshouses was found to be slow at day/night air temperatures of 10/5°C and to increase steeply with temperatures to 24/19°. Amongst the notable morphogenic influences associated with increasing temperatures in the glasshouses were poorer root development relative to top growth, thinner and smaller but more numerous leaves, and shorter and more numerous internodes. The elongation of individual leaves and internodes was faster but considerably less prolonged as temperatures increased. The E. regnans seedlings tested failed to prove thermoperiodically sensitive. It is concluded that the dormancy in shoot development observed in the field during winter is due to quiescence imposed by low temperatures, and that in the Tasmanian environment the pattern of growth and development of the vegetative shoots of E. regnans is directly and predominantly controlled by air temperatures throughout the year.

The cell cycle in vegetative and floral shoot meristems measured by a double labelling technique.

Abstract: A double labelling technique was used to measure the length of the cell cycle in the shoot apical meristem of Silene coeli-rosa L. plants kept in short days, in which they remained vegetative, or exposed to 7 long days, which induced flowering. The length of the cell cycle in the vegetative plants (those in short days throughout) was about 18 hrs. It was also 18 hrs, or somewhat longer, in plants which had been exposed to long-day conditions for 5 days, by which time 90% of the plants are committed to flower. When plants had been exposed to the full inductive period of 7 long days and had been transferred back again to non-inductive (short day) conditions, floral morphogenesis had just begun and the cell cycle had almost halved, to 10 hrs. The cell cycle was therefore unaltered during floral induction and shortened only at the onset of the growth of the flower itself.

A study on the population dynamics of the perennial plant species Chamaenerion angustifolium (L.) scop.

Abstract: From a study of differently aged populations of the perennial plant species Chamaenerion angustifolium a concept was deduced concerning the population dynamics of the species. The age structure was determined by counting the rings of periderm in the roots. After the establishment of seedlings vegetative propagation is the main factor in population development. The longevity of populations depends on exogenic factors, since older root samples—if isolated from the population—appeared to be as viable as were younger specimens. The oldest population studied had been able to persist for about thirty years due to the mineral cycle brought about by the population itself. In still developing populations a greater number of shoots tend to sprout from younger roots than from older roots, when compared per unit root weight. The shoot density in full-grown populations (in which further root expansion does not occur) is related to the root biomass per unit area. It was suggested that the allocation of reserve assimilates within the roots is an endogenic factor determining the shoot density. After the early sprouting phase the shoot development depends mainly on environmental factors.

Vegetative Propagation of Pinus sylvestris

Abstract: Methods for the vegetative propagation of Pinus sylvestris L from interfascicular shoots are described Using 5-year-old plants the outgrowth of interfascicular shoots was promoted by removal of terminal and lateral buds; this response was augmented substantially by application of cytokinin, tri-iodobenzoic acid, alar and morphactin alone and especially in combination The rooting capacity of shoot cuttings from interfascicular shoots appeared to be largely determined by the state of growth of the stock plant Cuttings from dormant stock plants subjected to short-day treatment followed by a period of low temperature gave the best rooting, especially when the cuttings themselves had been cold-stored prior to planting Rooting was optimal when such cuttings were treated with a mixture of 25 mg/l of indolebutyric acid and 25 mg/l of napthaleneacetic acid as a 48 h basal soak, and were planted on a heated mistbench under extended illumination; over 90% of such cuttings could be rooted These results are discussed in relation to bud activity, endogenous hormone levels and promoting tissue extracts also tested