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Showing papers on "Shoot published in 1971"


Journal ArticleDOI
TL;DR: In this article, a mechanism is proposed by which secondary products of nitrate reduction in the shoot control the uptake of nitrates by the roots, and the reduction is stoichiometric to the synthesis of malate.
Abstract: A mechanism is proposed by which secondary products of nitrate reduction in the shoot control the uptake of nitrate by the roots. KNO3 enters the roots and is translocated to the shoot where nitrate is reduced and, at the same time, malate is produced. The reduction of nitrate is stoichiometric to the synthesis of malate (1). Part of the K-malate moves down to the root system in which malate is oxidized, yielding KHCO3 which exchanges for KNO3. Nitrate reduction in the shoot promotes the synthesis of malate which, after its translocation to the root, allows the preferential uptake of nitrate. Thus, plants reducing large amounts of nitrate may take up the anion without a superfluous accumulation of the cation. Furthermore, the utilization of nitrate by the shoot regulates its uptake by the root.

316 citations


Journal ArticleDOI
TL;DR: An analysis of shoot extension growth of Rhizophora mangle is presented, based on the continuous observation of a small population over a period of two years, which provides phenological information for a tree which fits the general category of "evergrowing" although in South Florida the climate is distinctly seasonal.
Abstract: An analysis of shoot extension growth of Rhizophora mangle is presented, based on the continuous observation of a small population over a period of two years. This provides phenological information for a tree which fits the general category of "evergrowing" although in South Florida the climate is distinctly seasonal. Environment has a strong governing influence, but the general progression of events is mediated endogenously. Growth is morphologically non-articulate, without obvious flushes, so that the unit of growth is regarded as the single internode. The apical bud has a uniform construction throughout the year, consisting of three leaf primordia and associated stipules, the expansion of the oldest pair of leaf primordia coinciding with the initiation of a new pair. Consequently environmental control of growth is effected through developmental processes in the apical bud. The rate of leaf expansion and leaf fall is at a peak in summer when temperatures and radiation levels are highest. Leaf fall is closely correlated with leaf expansion so that there is a relatively constant number of leaves on a shoot. However, there is some evidence that propagule abscission also affects leaf fall. All lateral organs (vegetative branches, inflorescences, and suppressed axillary buds) are developed within the apical bud, the types of organ differentiated at any one node apparently depending on plastochron length. This is most evident with regard to precocious (sylleptic) branches which are produced periodically in groups of from one to three. Suppressed axillary buds are very reduced and subject to apical dominance. When released from this. by pruning for example, they can reach a size which permits them to grow out as normal apical buds. Under continued apical dominance the life span of their potential for further growth is limited. Rhizophora mangle is, in a general sense, "everflowering" but expansion of flower buds is most frequent in summer, leading to a peak of fruit production about 4-7 months later and the largest crop of propagules 4-6 months later still. These observations are summarized in the form of a model which indicates how a single reproductive shoot might appear during this cycle, and how the population, as a whole, behaves. A hypothetical model of interrelationship between phenological phenomena is also presented as a basis for further work. The models serve to illustrate how shoot growth occurs in this tropical species, and how this is in marked contrast to the more familiar patterns of shoot growth in temperate trees. THE MOST DIVERSE floras of the world occur in the tropics where trees are usually the dominant life form. Despite this the study of the growth and development of tropical trees has been neglected (Tomlinson and Gill 1971) and present heories of tree behavior are based almost entirely on a few relatively well-studied north temperate xamples. Investigations of a wider range of tropical species should be made in order to extend our knowledge and add perspective to current theories of tree growth. This present study of shoot growth was undertaken with this ideal in mind using a widespread tropical species Rhizophora mangle L. which extends into subtropical Florida. The study continues the series of papers dealing with various aspects of the growth and anatomy of this species (Gill and Tomlinson 1969, 1971). Twig morphology of north temperate trees is characterized by segments delimited by series of bud scale scars. These articulations occur at the bases of branches and at intervals along them in such a way that they reflect he seasonal cessation of growth imposed by the severe winter climate. In contrast o this, Rhizophora shows no obvious articulation in the shoot system, an observation which led Koriba (1958) to place the Singapore species R. conjugata and R. macronata in his "evergrowing" category. South Florida has a seasonal climate, in contrast o the uniform climate of Singapore, and one might not expect the term "evergrowing" to apply to a species in a -non-uniform climate. The ability of an "evergrowing" species to flourish in a seasonal climate is investigated in this present article. A number of recent studies of north temperate trees have related the type of extension growth of the tree to the composition of its terminal buds (e.g., Critchfield 1960, Gill 1971). A few similar studies have attempted to do this for individual tropiical tree species (Bond 1942, 1945) but not one of these studies has involved a species which has a non-articulate morphology and is, therefore, apparently "evergrowing." Known examples of growth types 1 Contribution to a study of the growth of native woody plants of South Florida supported by a grant to Dr. P. B. Tomlinson from the Michaux Fund of the American Philosophical Society. Diagrams are the work of Priscilla Fawcett, Botanical Illustrator, Fairchild Tropical Garden. 2 Present address: Division of Plant Industry, C.S.I.R.O., P.O. Box 109, Canberra A.C.T. Australia 2601. 31Present address: Harvard Forest, Petersham, Massachusetts 01366 U.S.A. BIOTROPICA 3(2): 109-124 1971 109 in trees as a whole have been considered in a recent review by Tomlinson and Gill (1971) in a very general way where the suggestion is made that there are unlimited ways in which growth can be expressed in tropical trees. An earlier paper in this series on Rhizophora (Gill and Tomlinson 1969) described and illustrated the general morphology of R. mwngle and this provides a background for the present study in which extension growth and reproductive events are considered in relation to the seasonal changes in the environment. Radial growth has not been investigated despite its possible relationship to other phenological events. MATERIAL AND METHODS The source of material was a population of red mangrove in the vicinity of Fairchild Tropical Garden, Miami, Florida on the edge of Biscayne Bay. Climatically, the area is characterized by a warm humid summer and a relatively cool dry winter. Both maximum and minimum temperatures are high in summer when insolation reaches its highest value. Representative values for the period of observation are shown in figure 1. In winter, maximum temperatures may be high but minimum temperatures can fall close to freezing. Rainfall is spoiradic in winter and long periods without rain are common. In contrast, rain in summer is frequent and heavy. The annual average is 58 in (153 cm). Soils in the mangrove zone always remain wet and salinity varies according to tide, rainfall, and evaporation. The plants studied were 0.5-4 m tall and occurred in an area of mineral soil inundated by brackish water. All reproductive stages may be observed at any time of the year. Consequently observations were begun at different times on three different sets of shoots showing a variety of reproductive stages. One of these sets (shoots 22-41) was chosen because of the apparent high vigor of its shoots and their abundant branching. Measurements were begun on shoots of set one (1-21) in November 1968; on shoots of set two (22-41) in December 1968; on shoots of set three (42-58) in March 1969. Observations on all shoots continued until December 1970. The 58 shoots measured belonged to a total of 22 plants.

181 citations


Journal ArticleDOI
TL;DR: Evidence is presented that normal growth of axillary shoots occurs even when all mineral ions have to be obtained by translocation from the lower compartment.
Abstract: A B S T R A C T Rooted stems of three aquatic species were cultured in a two-compartment apparatus which allowed the upper and lower portions of the stem to be kept in different nutrient solutions. p32 was supplied to either the upper or lower compartment. At the end of a 10-day growth period, the specific activity of phosphate was determined in axillary shoots which developed during the course of the experiment from buds in the upper compartment. The results indicated that most of the phosphate in these shoots was not absorbed from the ambient medium but was derived from the rooted stem base in the lower compartment (over 90 % in Myriophyllum brasiliense, 59 % in M. spicatum, and 74 % in Elodea densa). These results give a very different but probably more accurate picture of phosphate absorption in rooted aquatic vascular plants than short-term experiments, in which phosphate is readily taken up from the ambient medium by leaves of M. spicatum and E. densa. In M. brasiliense the amount of phosphate translocated is related to the mass of roots present. Evidence is presented that normal growth of axillary shoots occurs even when all mineral ions have to be obtained by translocation from the lower compartment.

150 citations


Journal ArticleDOI
TL;DR: In a comparison of shoot removal and shoot tip removal starting 15 days after full bloom on Fortune trees, both treatments improved set, but whereas shoot removal caused a heavier ‘June drop’ compared with untreated trees, shoot Tip removal increased the number of fruits retained to harvest and produced a yield increase.
Abstract: SummaryFruit set was increased by removing all shoots 5 days after full bloom and at weekly intervals thereafter from trees of Sunset and Laxton’s Fortune, but removing shoots from Fortune trees 25 days after full bloom produced no beneficial effect on fruit retention. All treatments resulted in a heavier rate of fruit shedding during the ‘June drop’ period than occurred from control trees, and at harvest the trees without shoots had fewer fruits, and lower yields, than the controls. In a comparison of shoot removal and shoot tip removal starting 15 days after full bloom on Fortune trees, both treatments improved set, but whereas shoot removal caused a heavier ‘June drop’ compared with untreated trees, shoot tip removal increased the number of fruits retained to harvest and produced a yield increase. The difference between the two treatments in their influence on fruit retention, during and after the ‘June drop’, is accounted for by the beneficial effect of a relatively small number of leaves on each tipp...

121 citations


Journal ArticleDOI
TL;DR: It is found that the rhythm of shoot growth persists under controlled environmental conditions and that growth under these conditions is asynchronous, as it appears to be in the field, and data strongly suggest endogeneity.
Abstract: A B S T R A C T The shoot-growth rhythm of tropical trees is a little understood phenomenon. Correlations of tree growth with environment, deteimined from field studies in the tropics, have been largely inconclusive, and few studies have been done under controlled environmental conditions. As an initial part of a project to study shoot-growth rhythms in tropical trees this paper describes the rhythm in Theobroma cacao L. An individual shoot passes through alternate periods of growth and dormancy. The growth period is characterized by the expansion of leaves and elongation of the shoot. During dormancy the length of the shoot remains constant, and no new leaves expand. Shoot-growth rhythm was divided into phases. Dissection of shoot tips from the various phases shows that the total number of leaves and leaf primordia in the shoot apex remains constant during the dormant period and does not increase until the onset of the growth period. This indicates that activity of the apical meristem as well as leaf expansion and shoot elongation are rhythmic. We found that the rhythm of shoot growth persists under controlled environmental conditions and that growth under these conditions is asynchronous, as it appears to be in the field. Our data strongly suggest endogeneity.

114 citations


Journal ArticleDOI
TL;DR: The young leaves' consumption proper of photosynthates and their contribution to the growth of flowers, fruits and shoots by exposing spurs and shoots to 14CO2 at the earliest stages of the growth period in apples were studied.
Abstract: The young leaves' consumption proper of photosynthates and their contribution to the growth of flowers, fruits and shoots by exposing spurs and shoots to 14CO2 at the earliest stages of the growth period in apple trees (Malus X domestica) were studied. By a parallel determination of the growth intensity in various organs an attempt is made to evaluate their relative dependence on current photosynthates and on reserves from inside the tree. The proper fixation of 14C by growth in the exposed leaves is high in the earliest phases of growth. The fixation of 14C is considerable in the flowers, including the petals, immediately prior to flowering, in intensely growing fruits, and in the woody parts of the current year's shoots, when the main part of the terminal growth has been completed. Under conditions of high intensity of growth in an organ, the total fixation by growth in the parts studied may amount to as much as 80–90% of the 14C absorbed. Only in the very earliest phases of development does the growth of flowers and shoots appear to be based to a greater extent on materials supplied from reserves than from current photosynthesis. Quantitatively the greater part by far of the total new growth in fruits and shoots appears to be based on materials from current photosynthesis.

111 citations


Journal ArticleDOI
TL;DR: It is suggested that one of the first effects of flooding is to reduce GA levels and so inhibit stem elongation and at a later stage of waterlogging GA3 is less effective and other factors appear to inhibit shoot growth.
Abstract: Flooding of tomato roots results in decreased stem growth. We have shown that flooding will reduce levels of gibberellins (GA) in the roots, shoots, and bleeding sap of tomato plants. The adventitious roots that appear on the third day of waterlogging may be responsible for the production of GA that accumulate in the shoot after 3 to 4 days of flooding. The endogenous GA of tomato will stimulate stem growth of tomato plants. Initially, application of gibberellic acid (GA3) will stimulate the growth of flooded plants to a greater extent than that of non waterlogged plants. It is suggested that one of the first effects of flooding is to reduce GA levels and so inhibit stem elongation. At a later stage of waterlogging GA3 is less effective and other factors appear to inhibit shoot growth.

79 citations


Journal ArticleDOI
TL;DR: It was found that plant growth, shoot/root dry weight ratio, relative water content, and potassium concentration decreased under salinity in cultivated and wild plants, but chloride and sodium concentrations and leaf succulence increased in all three plant types.
Abstract: The species used in this study were the cultivated tomato Lycopersicon esculentum, the wild species L. peruvianum, and plants originating from the wild species L, esculentum minor. The three plant types were compared in control and sodium chloride solutions for stability of fruit size, growth, dry weight, leaf relative water content and succulence, and chloride, sodium, and potassium contents. Fruit size decreased under salinity in the cultivated species but remained unchanged in the wild plants. It was also found that plant growth, shoot/root dry weight ratio, relative water content, and potassium concentration decreased under salinity in cultivated and wild plants. In all instances, except for potassium, the decrease was smaller in the wild plants. However, chloride and sodium concentrations and leaf succulence increased in all three plant types. Increases in chloride, sodium, and leaf succulence were greater in the wild plants. The differences in response to salinity between the cultivated and the wild plants and their significance are discussed.

75 citations


Journal ArticleDOI
TL;DR: Young vegetative clones of yellow nutsedge were propagated by subdivision of older clones and then grown 6 months under photoperiods of 8 to 24 hr, and certain active vegetative processes-total peripheral shoot development, rhizome proliferation, and rate of higher order shooting- were progressively promoted.
Abstract: Young vegetative clones of yellow nutsedge (Cyperus esculentus L.) were propagated by subdivision of older clones and then grown 6 months under photoperiods of 8 to 24 hr. Early stages of development of basal bulbs, tubers, and flowering structures were characterized in terms of apical meristem activity and differentiation of various foliar appendages: cladophylls, prophylls, leaf primordia, foliar tube development, and involucral leaves. Ramification of the axial stem system was interpreted as a repeating phylogenetic sequence: viz., undifferentiated axial meristem (from basal bulb) a primitive stem (rhizome) a advanced stem (new basal bulb). New photosynthetic leaves differentiated every 4.5 to 5 days, and each exhibited a sigmoid pattern of growth for 24 to 40 days. As photoperiods increased from 14 to 24 hr, certain active vegetative processes—total peripheral shoot development, rhizome proliferation, and rate of higher order shooting—were progressively promoted. The rate of differentiation of indeterminate rhizome tips into basal bulbs (new shoots) was maximum at 16 hr and into tubers at 8 to 12 hr. Delayed tuberization, however, occurred even at the longest photoperiod. Flowering occurred only at photoperiods of 12 and 14 hr. Active vegetative processes were competitive with tuberization, and flowering was competitive with both active and dormant vegetative development.

68 citations


Journal ArticleDOI
TL;DR: Results corroborate and extend previous results, in that light is not required for nitrate reductase induction per se in leaves of dark-grown seedlings but is required to reactivate the protein synthetic apparatus of older leaves.
Abstract: Nitrate reductase can be induced in excised shoots of 3-day-old dark-grown Zea mays (var. WF9 × M14) seedlings in the absence of light. In contrast, leaves of 10-day-old dark-grown seedlings require a light treatment in order to induce enzymatic activity. Leaves of 10-day-old dark-grown seedlings contain a very low level of polyribosomes while 3-day-old shoots contain a very high level of polyribosomes. There is a gradual loss of polyribosomes from 3 to 10 days and a gradual loss of in vitro protein synthetic activity of the ribosome preparations. The loss of polyribosomes and decrease in their amino acid-incorporating activity correlate positively with the loss of ability to induce nitrate reducase activity as leaves of dark-grown corn seedlings age. These results corroborate and extend our previous results, in that light is not required for nitrate reductase induction per se in leaves of dark-grown seedlings but is required to reactivate the protein synthetic apparatus of older leaves.

68 citations


Journal ArticleDOI
TL;DR: The formation of blind shoots and malformed flowers in rose plants grown under various temperatures and light intensities, and subjected to different cut back procedures has been studied.
Abstract: The formation of blind shoots and malformed flowers in rose plants grown under various temperatures and light intensities, and subjected to different cut back procedures has been studied. Low temperature, low light intensity and low cut back promoted blind shoot formation. Hybrid tea cultivars are more sensitive for unfavourable temperature, light and cut back treatments than Floribunda cultivars. The process of floral abortion is initiated during the early stages of shoot growth before the differentiation of floral parts has been completed. Low temperatures (12–15°C) in this critical stage of development strongly promote blind shoot formation, but have no effect when stamen and pistil primordia had been formed in the apical flower bud. The formation of malformed flowers, so-called “bullheads”, which have significantly more petals than normal flowers, is also promoted by low temperature and low cut back. Light intensity seems to have no effect. Shoots subjected to low temperature (12°C) during the early stages of development, before the differentiation of the floral organs are fully completed, produce malformed flowers to a greater extent than shoots subjected to high temperature (18–24°C) during this period. It is suggested that blind shoot formation in roses is subject to hormonal control.

Journal ArticleDOI
13 Apr 1971-Botany
TL;DR: The data are interpreted as indicating that root and shoot GA's are interrelated in that the GA1 in the shoot originates in the root system.
Abstract: Removal of root apices from light-grown Phaseolus coccineus seedlings inhibited shoot growth. This inhibition was partially overcome by treatment with gibberellin A3. Extracts from control seedlings and seedlings without root apices were purified with G-10 Sephadex, chromatographed on silicic acid partition columns, and tested for GA-like activity with the 'Tan-ginbozu' dwarf rice and barley aleurone α-amylase bioassays. The major GA in control plants was GA1; traces of GA19 were also detected. Removal of root apices resulted in the disappearance of GA1 and the accumulation of GA19 in the leaves and apical buds and in the subapical root remnants. Gibberellin A1 levels in the cotyledons were unaffected by the removal of the root apices.The data are interpreted as indicating that root and shoot GA's are interrelated in that the GA1 in the shoot originates in the root system. Synthesis of the cotyledon GA1 appears to be independent of GA metabolism in the roots. A scheme is proposed that involves the recycli...

Journal ArticleDOI
TL;DR: The results of this study show that invasion and rapid encroachment of S. pyramidatus on C. dactyloides are pri- marily due to an allelopathic effect, with competitive mechanisms and mechanical disturbance probably accentuating this effect.
Abstract: Field observations of stands of Sporobolus pyramidatus indicated a reduction of growth of S. pyramidatus in the center of the stands. Associated species were either reduced in growth or eliminated from these stands. Rapid encroachment of S. pyramidatus on Cynodon dactylon was also observed. Experiments were designed to determine if the observed vegetational patterning was a result of allelopathy. Early studies eliminated shading and soil factors as causal agents. Experiments with field soil taken from around S. pyramidatus plants indicated that phytotoxins were present and were relatively stable in the soil. Decaying shoot material exerted the most phytotoxic effect on growth and germination of the test species; however, C. dactylon was adversely affected by all factors tested except leaf leachate. Buchloe dactyloides was inhibited by field soils and, by decaying shoots. The decaying shoots of S. pyramidatus inhibited the growth of its own seedlings. There was also an indication that the leaf leachate and root exudate of S. pyrami- datus may be responsible for its own decline. Para-coumaric acid and ferulic acid were extracted from S. pyrami- datus shoot residue in large quantities. Both compounds were very inhib- itory to germination of Amaranthus palmeri seed. The results of this study show that invasion and rapid encroachment of S. pyramidatus on C. dactylon and possibly on B. dactyloides are pri- marily due to an allelopathic effect, with competitive mechanisms and mechanical disturbance probably accentuating this effect. S. pyramidatus is more inhibitory to C. dactylon than to itself, thus allowing it to invade new areas before it eliminates itself.

Journal ArticleDOI
TL;DR: Chronic exposure of Pinto bean plants to levels of ozone sufficient to cause foliar injury adversely affected shoot and root growth and vigour and enhanced senescence and these effects were reflected in quantitative rather than qualitative differences in the successional root surface fungi.


Journal ArticleDOI
TL;DR: The results indicate that suckering in roots of intact aspen plants is prevented by auxin transported into the roots from growing shoot parts.
Abstract: Experiments with small plants of Populus tremula L. growing in solution culture indicate that polarly transported auxin is an important factor in the control of axillary bud growth. If the auxin supply from the growing apex is eliminated, the number of buds released is influenced by factors translocated in the transpiration stream from the roots. Suckers may be induced to develop from aspen roots, the age of which is six weeks or more. Removal of the growing apex and the axillary buds or stoppage of shoot growth by short day treatment were effective in inducing abundant suckering in small aspen plants. Some mature leaves had to be maintained, indicating the dependence of sucker formation on carbohydrate supply. These treatments are known to decrease auxin production in the shoots. Extraction and biological assay showed a decrease in the content of auxin in the roots as a consequence of removal of growing shoot parts. The results indicate that suckering in roots of intact aspen plants is prevented by auxin transported into the roots from growing shoot parts.

Journal ArticleDOI
01 Mar 1971-Botany
TL;DR: Cone production responses to treatment, and cone crop variation over several years were correlated with reduced bud failure during the period of new shoot elongation, indicating a predetermined potential for annual cone production and that cone crop periodicity is determined by later conditions favorable or unfavorable to continued early bud development.
Abstract: Partial girdles were applied in August, 1957, to one stem of two double-stemmed, 20-year-old Douglas fir (Pseudotsuga menziesii (Mirb.) Franco). The second stem served as control. A third double-stemmed tree was treated in May, 1958. Cone production responses were obtained on all three girdled stems, averaging 7.4 times that of control stems in 1959, and 1.6 and 2.3 times that of control stems in 1961 and 1962. Cone production responses to treatment, and cone crop variation over several years were correlated with reduced bud failure during the period of new shoot elongation. Total number of buds per shoot was initially similar for paired stems. These relationships indicated a predetermined potential for annual cone production, and that cone crop periodicity is determined by later conditions favorable or unfavorable to continued early bud development. Treatment increased both sugars and starch in shoots sampled 40 days after August girdling, but only starch remained elevated the next spring and throughout ...

Journal ArticleDOI
TL;DR: Aureobasidium pullulans was frequently isolated from surface-sterilized living twigs, buds, leaves and seeds of sycamore, and from twigs of horse-chestnut and lime and diminished in the roots during the first year of growth.
Abstract: Aureobasidium pullulans was frequently isolated from surface-sterilized living twigs, buds, leaves and seeds of sycamore, and from twigs of horse-chestnut and lime. The distribution of the fungus in the sycamore is described. It was isolated from roots and shoots of seedlings, but diminished in the roots during the first year of growth.

Journal ArticleDOI
TL;DR: It is concluded that control of protein hydrolysis in pea cotyledons is not mediated through the level of protease enzymes, as indicated by the proteolytic activity of tissue extracts, or by the amount of soluble nitrogen compounds accumulated.

Journal ArticleDOI
TL;DR: In this article, short-term uptake tests (48 hr) disclosed that increasing levels of Ca in solution cultures decreased both Sr and Ba uptake by bush beans and decreased the proportions of them remaining in roots compared with that transported to leaves.
Abstract: Short-term uptake tests (48 hr) disclosed that increasing levels of Ca in solution cultures decreased both Sr and Ba uptake by bush beans and decreased the proportions of them remaining in roots compared with that transported to leaves. Barium uptake was greater than Sr, and the concentration of both of these elements was highest in roots and lowest in leaves. Calcium accumulation was highest in stems and lowest in leaves. Uptake of Sr and Ba by roots showed little temperature dependency, but long-distance transport to shoots was temperature dependent as is known for Ca. Strontium and Ca and also Ba to a lesser extent served as stable-element carriers for transport of Sr⁸⁵ isotope into bush beans, but Mg did not. A level of 10⁻²M Ba in nutrient solution was toxic to the plants; that which was transferred to shoots killed the leaves. Its effect on permeability resulted in large transfer of Sr⁸⁵ to shoots. Long-term uptake tests (90 days) with tobacco grown in solution culture disclosed that Ca accumulated more in leaves while Sr and Ba accumulated more in roots. Two desert-plant species, Lycium andersonii and Lycium pallidum, showed interesting differences in their accumulation of these elements. L. andersonii tended to concentrate Ca in leaves, but Ba was concentrated in roots with Sr equally divided between roots and leaves. L. pallidum concentrated all three of these cations more in roots than in leaves.

Journal ArticleDOI
TL;DR: It is suggested that a dilute nutrient solution could provide sufficient nutrients for adequate root growth prior to major shoot growth, at which time a more concentrated nutrient solution is needed.
Abstract: Soybean plants (Glycine max L. Merr. var. Hawkeye), grown in nutrient solutions maintained at graded concentrations showed a large response in both shoot dry weight and total ion uptake. Growth rate was dependent upon nutrient concentration, even when quantity of nutrient was not limiting. Peak periods for absorption of specific ions at certain growth stages were not exhibited. Rates of ion uptake by soybeans were generally proportional to the growth rate during the period of major growth. It is suggested that a dilute nutrient solution could provide sufficient nutrients for adequate root growth prior to major shoot growth, at which time a more concentrated nutrient solution is needed.

Journal ArticleDOI
TL;DR: Cold-treated shoots acquire the capacity for rapid transport 7 days after they are placed into favorable growing conditions, at which time dormancy callose disappears from the phloem, respiratory activity of the stem tissue increases, and mitotic reactivation occurs in the bud.
Abstract: Transport of indoleacetic acid-1(14)C following application to the buds of intact white ash (Fraxinus americana L.) shoots proceeds at a velocity of about 1.3 centimeters per hour in actively growing seedlings, but only 0.3 centimeter per hour in dormant seedlings. The rapid movement is metabolically controlled, and at 1 C or in a nitrogen environment it is reduced to 0.2 centimeter per hour, suggesting that the slower movement is due to diffusion. The transport profile for growing shoots shows a logarithmic decrease in activity in stems treated for 3 hours. However, over longer treatment intervals, especially after 12 hours, a steady state of recoverable activity occurs in the more basal stem segments. Cold-treated shoots acquire the capacity for rapid transport 7 days after they are placed into favorable growing conditions, at which time dormancy callose disappears from the phloem, respiratory activity of the stem tissue increases, and mitotic reactivation occurs in the bud. Following shoot reactivation, the velocity and amount of exogenously supplied indoleacetic acid transported remained relatively uniform until the onset of the succeeding dormant period. Five per cent, or less, of the applied tracer moves into the shoot, with substantial portions remaining as indoleacetic acid.

Journal ArticleDOI
TL;DR: Water vapor loss through cuticle damaged by the sporulation process, together with the reduction in root to shoot ratio which occurs in diseased plants, upset the water economy of the diseased plant under mild drought conditions.
Abstract: Bean plants (Phaseolus vulgaris L.) infected with the rust Uromyces phaseoli became unusually susceptible to drought as sporulation occurred. Under the conditions used (1,300 ft-c, 27 C, and 55% relative humidity) such plants wilted at soil water potentials greater than -1 bar, whereas healthy plants did not wilt until the soil water potential fell below -3.4 bars. Determinations of leaf water and osmotic potentials showed that an alteration in leaf osmotic potential was not responsible for the wilting of diseased plants. When diffusive resistance was measured as a function of decreasing leaf water content, the resistance of healthy leaves increased to 50 sec cm(-1) by the time relative water content decreased to 70%, whereas the resistance of diseased leaves remained less than 8 sec cm(-1) down to 50% relative water content. Apparently, water vapor loss through cuticle damaged by the sporulation process, together with the reduction in root to shoot ratio which occurs in diseased plants, upset the water economy of the diseased plant under mild drought conditions.


Journal ArticleDOI
TL;DR: Germination results indicated that Michigan seeds required cold treatment prior to germination in a 65-85 F treatment, but that seeds from North Carolina did not require cold treatment and germinated well in either 65- 85 F or 65-95 F treatments.
Abstract: Seed germination response to temperature and salinity and seedling response to daylength, temperature, and salinity were studied in Ammophila breviligulata Fern from Michigan and North Carolina Germination results indicated that Michigan seeds required cold treatment prior to germination in a 65-85 F treatment, but that seeds from North Carolina did not require cold treatment and germinated well in either 65-85 F or 65-95 F treatments. During germination, North Carolina seeds were more salt-tolerant and less sensitive to high temperatures than seeds from Michigan Seedling studies revealed that best vegetative growth by both populations occurred under long-day conditions with daytime temperatures between 70 and 80 F Growth of Michigan seedlings was more restricted under short daylengths at lower temperatures and also by high temperatures under both short- and long-day conditions than growth of North Carolina seedlings. Michigan seedlings generally contained more shoot moisture and had higher chlorophyll co...

Journal ArticleDOI
TL;DR: Young to mature, conventionally managed, single-stem, deblossomed and fruiting Arabica coffee trees growing in a fertile lateritic clay loam at Ruiru, were uprooted at 2- to 3-monthly intervals between February 1967 and June 1968 and analysed for organic-N, and total P, K, Ca and Mg.
Abstract: SUMMARY Young to mature, conventionally managed, single-stem, deblossomed and fruiting Arabica coffee trees growing in a fertile lateritic clay loam at Ruiru, were uprooted at 2- to 3-monthly intervals between February 1967 and June 1968. Each was divided into ten parts which were dried, weighed, completely ground, and analysed for organic-N, and total P, K, Ca and Mg. Mature trees took up about 100 g N, 6 g P, 100 g K, 35 g Ca and 10 g Mg each per annum, of which 8-29 % (depending on the element) would be removed in an average crop of fruits, and 50-81 % returned to the soil in prunings and fallen leaves. About half the P and K in senescing leaves was returned to the tree. N, K, Ca and Mg uptake by deblossomed trees was relatively rapid when they produced a large post-drought ‘flush’ of shoot growth in February-April 1967. Thereafter uptake kept pace with changes in dry weight, and the concentration of N, K, Ca and Mg in the tree parts changed relatively little. By contrast, P-uptake was relatively rapid over the cool, dry season 1967 (June-September), when the roots < 1 mm diameter grew rapidly, and during the subsequent Short Rains, but was slow during the hot, dry season 1968 (December-March) when the surface 2-3 ft of soil dried out. The concentration of P in the trees changed accordingly, especially in the branches. The flower buds took 39 % of the small total P-uptake during the hot, dry season 1968. Trees bearing a light or moderate crop of fruits absorbed all the minerals determined more rapidly than deblossomed trees. The fruits on heavily fruiting trees took 89,95,98 and 99 % of the net current increment in Mg, K, organic-N and P, respectively, but only 39 % of the Ca. All leaves on the fruiting trees became rich in Ca, and most of their woody parts were depleted of P. Mineral uptake in a coffee plantation is compared with that in plantations of other woody perennial crops, and some practical implications are noted in relation to soil and plant factors affecting the mineral nutrition of coffee in Kenya, with special reference to phosphates.

Journal ArticleDOI
TL;DR: To elucidate what controls flowering, Xanthium was chosen because it has been so thoroughly investigated and has a cluster of intriguing differences from Perilla in its flowering physiology (such as its much greater "sensitivity" to photoinduction-cf Evans, 1969).
Abstract: Conditions were developed for the sterile culture of shoot tips of Xanthium pensylvanicum Wallr. for use as a bioassay for flower-controlling chemicals. By using a modified Murashige-Skoog medium (minus the auxin but including kinetin) and light intensity much higher than usual for plant tissue cultures, fast growth and development of the shoot tips was achieved. Under short-day conditions (8 hr day: 16 hr night), the cultures from vegetative shoots flowered and fruited; under noninductive conditions (using a 2 hr light-break in the middle of the dark period), the shoot tips continued vegetative development. Both intact plants and cultured tips could be photoinduced in the first days after germination. Ecdysterone, a potent insect moulting hormone, was tested in the bioassay system. It was without either qualitative or quantitative effect on flowering or vegetative development on either cultured shoot tips or intact plants irrespective of whether they were under inductive or noninductive photoperiodic conditions. DESPITE ATTEMPTS by researchers who had extensive experience with sterile cultures (e.g., Wetmore, 1956), shoot tips of the short-day plant (SDP) Xanthium have apparently not been successfully cultured. It would be useful to accomplish this for two reasons. First, earlier cultures of the shoot tips of the SDP Perilla had provided interesting confirmation and extensions of the hypothesis that leaves in long day (LD) were actively inhibiting flowering, because Perilla shoot tips even when cultured in LD developed inflorescences up to the sporogenous stage if the larger and older leaves were excised before implanting (Raghavan and Jacobs, 1961). If the youngest two leaf-pairs below the apical bud were not excised, however, the cultures remained vegetative under LD conditions (although they flowered under SD). To elucidate what controls flowering, it is of obvious interest to see if the results from Perilla apply to other photoperiodically sensitive genera. Xanthium was chosen because it has been so thoroughly investigated and has a cluster of intriguing differences from Perilla in its flowering physiology (such as its much greater "sensitivity" to photoinduction-cf Evans, 1969). Secondly, if we succeeded in culturing Xanthium shoot tips but they remained vegetative in LD, we planned to use the cultured apical buds as an improved 1 Received for publication 15 March 1971. Research supported by funds provided by the Eugene Higgins Trust Fund, by facilities made available by the Whitehall and John A. Hartford Foundations to the Department of Biology, Princeton University, and by a Hoyt Foundation grant and NSF grants to W. P. Jacobs. The aid of Anthony Procaccini in growing and maintaining the plants, of Susan Kirk in the early culture work, and of Dan Suthers in taking the photographs is gratefully acknowledged. bioassay for testing flower-promoting extracts and solutions. Cultured buds would serve as improved bioassay material because they would be sterile (thus obviating artefacts from bacterial interactions with compounds added). They would also be a simpler system than the whole plant: we would be testing the flower-inducing activity of an extract more directly by adding it to a cultured apical bud rather than to the older leaves of the complete plant. In the latter case, active material in the extract would have to penetrate the leaf, avoid metabolism there, be moved out of the leaf and up the stem to the reactive meristem and there bring about the changed activity that results in flowering. By using cultured buds we hoped to "isolate" the major reactive system (as suggested by the "PESIGS" rules, Jacobs, 1959), and avoid these secondary pitfalls. [Other investigators have independently thought of using cultured shoot tips as bioassays for flower-promoting extracts (e.g., Nitsch and Nitsch, 1967; Nitsch, 1968).] The current paper reports on progress made since We started culturing Xanthium in mid-1965. Our first results with cultured buds forced us to re-examine thoroughly floral development in intact Xanthium plants because we discovered that the normal development of the many separate male and female inflorescences was inadequately represented by descriptions restricted to the single, terminal, male inflorescence, as used by most earlier physiologists studying Xanthium flowering. This fuller description of normal floral development is now published and was used for interpreting the cultures (Kirk, Morrow, and Jacobs, 1967). One of our aims was to be ready to use a wider variety of cultural conditions than tissue culturists


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TL;DR: Studies with a fluorescence spectrophotometer and gas chromatography confirm earlier results that IAA occurs in buds and sprouting shoots of Scots pine.
Abstract: Studies with a fluorescence spectrophotometer and gas chromatography confirm earlier results that IAA occurs in buds and sprouting shoots of Scots pine. IAA could be found during the whole vegetation period but not during winter dormancy. The largest amount was obtained during shoot growth in spring and early summer. During the most intensive elongation phase, a gradient could be found in the concentration of auxin with the highest amount in the basal part and a decreasing concentration upwards in the shoot.

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TL;DR: Reactions of leaves on various kinds of branches were similar to those on main stems except that leaves on flower shoots showed more frequent occurrence of reaction types 3 and 4 and these reactions have been shown by plants grown in the open and in the glasshouse.
Abstract: When potato plants cv. King Edward are inoculated with Phytophthora infestans by a standard method, which is described, four types of leaf reaction can be distinguished: (1) successful infection with fungal spread giving normal lesions, (2) relative hypersensitivity (as defined), (3) hypersensitivity (as defined) and (4) no visible symptoms. Leaves showing these reactions form zones on growing plants and up to three such zones can be present. In very young plants all leaves are very susceptible and show normal lesions. In older plants up to flowering time reaction types 2, 3 and 4 appear in a zone intermediate between susceptible zones with reaction type 1 at the top and base of the plant. In plants immediately after flowering there may be a less well-defined susceptible zone at the top of the plant so that temporarily only two clear zones are present. With further increase in leaf number the susceptible zone at the base increases in size, the intermediate more resistant zone remains constant in extent and a susceptible zone is again present at the top. The overall resistance of plants therefore varies with age and may be related to the occurrence of different reaction types. These reactions have been shown by plants grown in the open and in the glasshouse but are more apparent on leaves attached to the plant and, with the exception of normal lesions, are much less frequently seen on detached leaves. Reactions of leaves on various kinds of branches were similar to those on main stems except that leaves on flower shoots showed more frequent occurrence of reaction types 3 and 4. When the concentration of sporangia in the inoculum applied to leaves on main stems was 5000/ml reaction types 3 and 4 were most frequent but were somewhat fewer at a concentration of 10000 sporangia/ml and least at concentrations between 25000 and 100000 sporangia/ml.