Showing papers on "Shoot published in 1980"

Xylem Transport of 1-Aminocyclopropane-1-carboxylic Acid, an Ethylene Precursor, in Waterlogged Tomato Plants.

Abstract: Waterlogging is known to cause an increase in ethylene synthesis in the shoot which results in petiole epinasty. Evidence has suggested that a signal is synthesized in the anaerobic roots and transported to the shoot where it stimulates ethylene synthesis. Experimental data are presented showing that 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene, serves as the signal. Xylem sap was collected from detopped tomato plants (Lycopersicon esculentum Mill. cv. VFN8). ACC in the sap was quantitated by a sensitive and specific assay, and its tentative chemical identity verified by paper chromatography. ACC levels in both roots and xylem sap increased markedly in response to waterlogging or root anaerobiosis. The appearance of ACC in the xylem sap of flooded plants preceded both the increase in ethylene production and epinastic growth, which were closely correlated. Plants flooded and then drained showed a rapid, simultaneous drop in ACC flux and ethylene synthesis rate. ACC supplied through the cut stem of tomato shoots at concentrations comparable to those found in xylem sap caused epinasty and increased ethylene production. These data indicate that ACC is synthesized in the anaerobic root and transported to the shoot where it is readily converted to ethylene.

The development of waterlogging damage in wheat seedlings (Triticum aestivum L.), 1: shoot and root growth in relation to changes in the concentrations of dissolved gases and solutes in the soil solution

Abstract: SummaryThe effects of waterlogging on concentrations of gases and various solutes dissolved in the soil water were investigated in the laboratory, to determine whether the early disruption to the growth of wheat was most closely associated with depletion of dissolved oxygen, accumulation of toxins, or changes in concentrations of nutrient ions in the soil water. Waterlogging slowed shoot fresh weight accumulation, leaf extension and nodal root growth; it also caused death of the seminal root system and early senescence of the lower leaves. However, the shoot dry weight initially increased above that of the non-waterlogged controls, and thus was not a reliable indicator of the early restriction to plant growth and development. The symptoms of damage to shoots and roots were attributed to the fall in soil oxygen concentrations, rather than to any decrease in concentration of inorganic nutrients in the soil water, or to the accumulation of any other measured solutes to toxic concentrations.

The development of waterlogging damage in wheat seedlings (Triticum aestivum L.)

Abstract: Decreases in the concentrations of nitrogen, phosphorus, potassium, calcium and magnesium, in the shoots of wheat seedlings soon after the start of waterlogging were mainly attributed to an inhibition of ion uptake and transport by roots in the oxygen deficient soil. There was a small net accumulation of nitrogen, phosphorus and potassium by the aerial tissues, principally the tillers rather than the main shoot. By contrast, calcium and magnesium accumulated in both tillers and main shoot. With waterlogging, nitrogen, phosphorus and potassium were translocated from the older leaves to the younger growing leaves, and in the case of nitrogen this was associated with the onset of premature senescence. Calcium and magnesium were not translocated from the older leaves, the younger leaves acquiring these cations from the waterlogged soil. The promotion of leaf senescence by waterlogging was counteracted by applications of nitrate or ammonium to the soil surface, or by spraying the shoots with solutions of urea, but the beneficial effects on shoot growth were small.

Relation of internal phosphorus concentration and plant weight in plants infected by vesicular‐arbuscular mycorrhizas

Abstract: Summary Our own results and a search of the literature have shown that shoots of plants infected with vesicular-arbuscular mycorrhiza normally contain higher internal concentrations of P than those of uninfected plants of equal size, over wide ranges of external P supply and of host plants. Increased demand for carbon by infected roots is a possible explanation for this, and simple graphical methods of estimating the resulting dry wt loss are suggested.

Myo-Inositol Esters of Indole-3-acetic Acid as Seed Auxin Precursors of Zea mays L.

Abstract: Indole-3-acetyl- myo -inositol esters constitute 30% of the low molecular weight derivatives of indole-3-acetic acid (IAA) in seeds of Zea mays. [ 14 C]Indole-3-acetyl- myo -inositol was applied to a cut in the endosperm of the seed and found to be transported from endosperm to shoot at 400 times the rate of transport of free IAA. The rate of transport of indole-3-acetyl- myo -inositol from endosperm to shoot was 6.3 picomoles per shoot per hour and thus adequate to serve as the seed auxin precursor for the free IAA diffusing downward from the shoot tip. Indole-3-acetyl- myo -inositol is the first seed auxin precursor to be identified. Application of either [ 14 C]IAA or 14 C-indole-3-acetyl- myo -inositol ester to the endosperm results in both free and esterified [ 14 C]IAA in the seedling shoot. Esterification of free IAA and hydrolysis of indole-3-acetyl- myo -inositol occurred in the shoot and not the endosperm yielding ratios of ester to free IAA which approximate the ratios of ester to free IAA normally found in corn shoot tissue. This proves, for the first time, that esterified IAA and free IAA are interconvertible in the growing shoot. Since free IAA may be limiting for plant growth, knowledge that the free hormone is in “equilibrium” with its conjugates suggests new methods for the control of plant growth.

Biological activities of indoleacetylamino acids and their use as auxins in tissue culture.

Abstract: The auxin activities of a number of indoleacetylamino acid conjugates have been determined in three test systems: growth of tomato hypocotyl explants (Lycopersicon esculentum Mill. cv. Marglobe); growth of tobacco callus cultures (Nicotiana tabacum L. cv. Wisconsin 38); and ethylene production from pea stems (Pisum sativum L. cv. Alaska). The activities of the conjugates differ greatly depending on the amino acid moiety. Indoleacetyl-l-alanine supports rapid callus growth from the tomato hypocotyls while inhibiting growth of shoots and roots. Indoleacetylglycine behaves in a similar manner but is somewhat less effective in supporting callus growth and in inhibiting shoot formation. The other amino acid conjugates tested (valine, leucine, aspartic acid, threonine, methionine, phenylalanine, and proline) support shoot formation without supporting root formation or much callus growth. The tobacco callus system, which forms abundant shoots in the presence or absence of free indoleacetic acid, produces only rapid undifferentiated growth in the presence of indoleacetyl-l-alanine and indoleacetylglycine. The other conjugates inhibit shoot formation weakly if at all. Most of the conjugates induce sustained ethylene production from the pea stems but at rates well below the initial rates observed with free indoleacetic acid. Many, but not all of the effects of conjugates such as indoleacetyl-l-alanine can be mimicked by frequent renewals of the supply of free indoleacetic acid.

Effect of vesicular-arbuscular mycorrhizal fungi on the relations of plant growth, internal phosphorus concentration and soil phosphate analyses

Abstract: Summary The effect of infection by vesicular-arbuscular mycorrhiza on the predictive value of soil analysis for available P was tested in a glasshouse experiment. Leeks (Allium porrum) were grown on ten Rothamsted soils with a wide range of initial NaHCO3-soluble P, each of which also received 5 levels of added P. Soils were partially sterilized with 1 Mrad of γ-radiation, or left untreated; plants on sterilized soil were infected with yellow-vacuolate endophyte (Glomus mosseae) or left non-mycorrhizal. The NaHCO3-soluble P in the soils was measured 5 days after phosphate addition. Yields from all P levels on all soils were plotted against soil NaHCO3-soluble P content and separate smooth response curves were obtained for non-infected and artificially-infected plants. Infection increased yield only on soils with less than 100 mg P kg−1. In contrast, naturally-infected plants gave no clearly defined response curve to P, and on three soils the yields were consistently low. These soils gave very low natural infections and had low spore densities probably due to the cropping history of the sites. Artificially-infected plants had much higher shoot P concentrations than did uninfected plants of similar dry weight, over a large range of soil phosphate levels; this effect was also noted with the endophyte G. fasciculatus. Naturally-infected plants showed a poor relationship between shoot P concentration and yield.

Distribution of wheat germ agglutinin in young wheat plants.

Abstract: A liquid phase, competition-binding radioimmunoassay for wheat germ agglutinin, with a detection limit of 10 nanograms, was developed in order to determine the distribution of this lectin in young wheat plants. Affinity columns for wheat germ agglutinin removed all antigenically detectable activity from crude extracts of wheat tissue; thus, the antigenic cross-reactivity detected by the assay possesses sugar-binding specificity similar to the wheat germ-derived lectin. The amount of lectin per dry grain is approximately 1 microgram, all associated with the embryo. At 34 days of growth, the level of lectin per plant was reduced by about 50%, with approximately one-third in the roots and two-thirds in the shoot. The data also indicate that actively growing regions of the plant (the bases of the leaves and rapidly growing adventitious roots) contain the highest levels of lectin. Half of the lectin associated with the roots could be solubilized by washing intact roots in buffer containing oligomers of N-acetylglucosamine, whereas the remainder is liberated only upon homogenization of the tissue.

Fruit-set of unpollinated ovaries of Pisum sativum L. : Influence of vegetative parts.

Abstract: The influence of removing the apical shoot and different leaves above and below the flower on the fruit-set of unpollinated pea ovaries (Pisum sativum L. cv. Alaska) has been studied. Unpollinated ovaries were induced to set and develop either by topping or by removing certain developing leaves of the shoot. Topping had a maximum effect when carried out before or on the day of anthesis, and up to four consecutive ovaries were induced to set in the same plant. The inhibition of fruit-set was due to the developing leaves and not to the apex. The third leaf above the first flower, which had a simultaneous development to the ovary, had the stronger inhibitory effect on parthenocarpic fruit-set. The application of different plant-growth regulators (indoleacetic acid, naphthylacetic acid, 2,4-dichlorophenoxyacetic acid, gibberellic acid, benzyladenine and abscisic acid) did not mimic the negative effect of the shoot.

Promotion of sink activity of developing rose shoots by light.

Abstract: Holding young rose shoots (Rosa hybrida cv. Marimba) in darkness while the rest of the plant was in light reduced the amount of 14C assimilates recovered from the darkened shoot by half. Relative specific activity of the shoot tip grown in light was 13.5 times greater than that of the darkened one. The flower bud at the shoot tip degenerated in darkness and died. Shoots 2 to 3 centimeters long, after flower initiation, were most sensitive to the dark treatment. The degeneration is a gradual and reversible process in the first 8 days of darkness, followed by irreversible damage and atrophy. Darkening enhanced the ability of the young leaves to compete for the available assimilates over that of the darkened shoot tip. The enhancement of the mobilizing ability of the shoot tip by light is independent of photosynthesis since spraying with 3-(3,4-dichlorophenyl)-1,1-dimethylurea or holding shoots in a CO2-free atmosphere did not diminish the promoting effect of light on flower bud development or assimilate import. The possibility that light exerts its effect by photoproduction of ATP was also excluded inasmuch as no differences were found in ATP levels of shoot tips held in darkness and those held in light.

Mammalian epidermal growth factor promotes plant growth

Abstract: Application of mouse submaxillary gland epidermal growth factor to young sorghum seedlings at low concentrations (≈0.4-4 μM) increased shoot growth significantly over 3- and 6-day periods. The effects were dose dependent.

The influence of vesicular‐arbuscular mycorrhizas on phosphorus transfer between plants

Abstract: SUMMARY In six experiments Lolium perenne L. and Plantago lanceolata L. were grown together in pots. Two experiments also included L. perenne alone, P. lanceolata alone, or L. perenne + Trifolium repens L. In five of the experiments prior sterilization of the soil followed by reinoculation was used to obtain two treatments, one having plants infected with vesicular-arbuscular mycorrhiza, the other non-mycorrhizal. The shoots of some plants in each pot (‘donors’) were injected with 32P. After a week these shoots were removed, and after a further week the remaining plants (‘receivers’) were harvested and their 32P content determined. In all experiments and species-combinations there was some 32P transfer to the shoots of both mycorrhizal and non-mycorrhizal receiver plants. The amount of transfer in mycorrhizal treatments was 2 to 8-fold greater than in non-mycorrhizal treatments, except in one experiment where mycorrhizal infection was very low. There was no clear difference between the different species combinations in the amount by which phosphorus transfer was enhanced by mycorrhizas. These results show that mycorrhizas can increase phosphorus transport between plants, but do not show whether there is direct transport from one root to another via interconnecting hyphae or whether the phosphorus must leave the donor root before being taken up by mycorrhizal hyphae.

Culture of chestnut shoots from buds in vitro.

Abstract: SummaryA method is described of growing chestnut shoots in vitro from lateral buds of 3-4 month-old seedlings cultured in a nutrient medium. The addition of BAP to the culture medium, optimally at a concentration of 1 mg l-1 caused the development of axillary shoots. Zeatin induced more vigorous shoots, but with little development of axillary shoots. Kinetin had no effect, compared to the control, without cytokinin. An adverse effect on growth was observed when GA3 was added to the cultures. Sub-cultures of single shoots and nodes excised from shoots on the initial cultures were established in a medium with 0.1 mg l-1 BAP to promote further shoot multiplication.

Economy of Carbon and Nitrogen in Nodulated and Nonnodulated (NO3-grown) Cowpea [Vigna unguiculata (L.) Walp.]

Abstract: The response of non-nodulated cowpea (Vigna unguiculata (L.) Walp. cv Caloona) to a wide range of NO3 levels in the rooting medium was studied 40 days after sowing by in vitro assays of plant organs for NO3 reductase (EC 1.6.6.1) and analyses of root bleeding (xylem) sap for nitrogenous solutes. Plants fed 1, 5, 10, 20, and 40 millimolar NO3 showed, respectively, 64, 92, 94, and 91% of their total reductase activity in shoots and 34, 30, 66, 62, and 58% of the total N of their xylem sap as NO3. These data, and the absence in the plants of significant pools of stored NO3, indicated that shoots were major organs of NO3 assimilation, especially at levels of NO3 (10 to 40 millimolar) that maintained plant growth at near maximum rates. Partitioning and utilization of C and N were studied in nodulated, minus NO3 plants and non-nodulated plants fed 10 or 20 millimolar NO3, the levels of NO3 which gave rates of growth and N assimilation closest to those of the symbiotic plants. The conversion of the C of net photosynthate to dry matter was similar in nodulated plants (67%) and NO3-grown plants (64%), but greater proportions of photosynthate were translocated to below ground parts of nodulated plants (37%) than of NO3-fed plants (23 to 26%). Greater photosynthate consumption by nodulated roots was associated with proportionately greater root growth and respiration and 2-fold greater export of C in xylem than in the NO3-fed plants. Theoretical considerations suggest that the elevated CO2 output of nodulated roots was due not only to CO2 loss associated with nodule function, but also to a much greater nonassimilatory component of respiration in the supporting root of the nodulated plant compared to roots of the NO3-fed plants. Data are compared with previously published information from other legumes.

Influence of leaves and roots on meristem development inNicotiana tabacum L. cv. Wisconsin 38

Abstract: The terminal, apical shoot meristem ofN. tabacum cv. Wisconsin 38 normally differentiates into a flower after producing 30 to 40 nodes. The influence of leaves and roots on the regulation of flowering was evaluated by counting the number of nodes produced after removal of leaves or the induction of adventitious roots. Leaf removal has no effect on the number of nodes produced before flower formation. Root induction significantly increases the number of nodes produced before flower formation. The plant behaves as if it were measuring the number of nodes between the meristem and the roots as a means of regulating meristem conversion from vegetative to floral differentiation.

Plantlet formation from embryonic tissue of chestnut grown in vitro

Abstract: Development of axillary shoots was induced when isolated embryonic axes of chestnut (Castanea sativa Mill.) were cultured on a defined medium containing 6-benzyl-aminopurine (BAP). The optimal concentrations of BAP were determined for development of axillary shoots from both embryonic axes and subcultured shoots. After shoot multiplication a great number of shoots have been maintained sequentially without significant change in the proliferative rate for one year. Limited rooting has been obtained with excised shoots. Indole-3-butyric acid (IBA) at 2 mg/l was used to induce root primordia. After 8 days of treatment the plantlets were transferred to an auxin-free medium for root development.

Propagation of potato by shoot-tip culture. 1. Shoot multiplication

Abstract: Extensive proliferation via axiallary meristems can be induced in potato shoot-tips (15–20mm) cultured in liquid media. Proliferation is greatest when a 4-week period of shake culture for 1 1/2 h per day is followed by stationary culture. The rate of proliferation is influenced by light, temperature and phytohormones. Gibberellic acid and kinetin are essential, but the optimal concentrations are different for initial inocula and for subcultures. Under optimal conditions shoot multiplication rates in excess of 10–25 fold per 8 weeks are obtained, but there are genotypic differences in the response.

Tillage effects on root development, water uptake and growth of oats

Abstract: The experiment was carried out in 1976 on a well-drained, loess-derived soil. The general objective was to study the interrelation between root development, water uptake and shoot growth of oats (Avena sativa L.) under field conditions during one growing season. A specific purpose was to determine if regular tillage induces differences in rooting pattern, water uptake and plant growth as compared to untilled soil. In tilled soil a plough-sole layer at 20–30-cm depth induced higher rooting densities within the 10–20-cm layer, but restricted proliferation of roots in deeper layers. Accordingly, total water uptake from the 10–20-cm layer was greater and from the 20–60-cm layer it was less than from untilled soil. Water uptake was particularly limited in the plough-sole layer. The water uptake rate was functionally related to rooting density and soil water potential. Relative growth rate of root length decreased with increasing soil water tension and ended at approximately 19 bar. Tillage favored initial shoot growth, but in June accelerated shoot growth on untilled soil was associated with higher evapotranspiration and a deeper soil exploration by roots. Shoot growth rate was linearly related to transpiration rate. One mm of water use corresponded to a production of 40 kg/ha dry matter.