A Relationship between Length of Basis and Adventitious Root Formation in Pea Cuttings

A positive correlation between the length of the basis and the ability of the cuttings to form adventitious roots was observed in pea cuttings. Plants with a different basis length (the third internode) were obtained in different ways: Regulation by the level of irradiance, dark treatment or gibberellic acid. The length of the basis was also regulated by excision of the cuttings at different places on the stock plants. With increasing basis length an increase was found in the number of roots subsequently formed. The results were similar in cuttings from plants grown at different levels of irradiance or from dark treated plants. Optimal rooting was obtained by cutting the plants just above the second scale leaf. Cuttings from plants treated with 10^?3M GA₃ showed the same correlation between the length of the third internode and root formation as found in the other experiments, but the number of roots were at a lower level.     

Differences in Endogenous Levels of Gibberellin-Like Substances in Nodules of Phaseolus lunatus L. Plants Inoculated with Two Rhizobium Strains

Lima bean plants (Phaseolus lunatus L.) inoculated with Rhizobium sp. strain 127E14, which lacks constitutive nitrate reductase activity, were significantly taller after 4 weeks of age than plants inoculated with strain 127E15, which contains constitutive nitrate reductase activity. Plants inoculated with either strain responded to application of 5 micrograms gibberellic acid per plant with rapid internode elongation; plants inoculated with strain 127E15 became less responsive to gibberellic acid from 3 to 5 weeks of age, while plants inoculated with strain 127E14 did not. The height of plants inoculated with strain 127E14 was reduced by 20% with application of gibberellin biosynthesis inhibitors to the roots, while height of plants inoculated with strain 127E15 was unaffected.     

REGULATORY ROLE OF INDOLE-3-ACETIC ACID AND GIBBERELLIC ACID IN VEGETATIVE DEVELOPMENT OF XANTHIUM PENNSYLVANICUM

A single application of gibberellic acid to young internodes significantly accelerated the rate of internode growth and the rate of leaf production in shoots of Xanthium pennsylvanicum Wallr. The average duration of one plastochron in treated plants was reduced to 43% of control levels. Gibberellic acid also had a pronounced morphogenetic effect on leaves so that the area and leaf length of treated plants were both significantly reduced. Depending upon concentration, auxin had both inhibitory and promotive effects on Xanthium shoots. Indole-3-acetic acid markedly altered the response of the gibberellic acid-treated internodes and those located above and below the site of application. In addition, high auxin concentrations induced the formation of adventitious roots in treated internodes. Auxin also brought about significant reductions in the length and area of leaves developed under the influence of this hormone.     

Effects on the Stem of Winter Barley of Manipulating the Source and Sink during Grain-filling: II. CHANGES IN THE COMPOSITION OF WATER-SOLUBLE CARBOHYDRATES OF INTERNODES

Field-grown barley plants were manipulated by removing earsand by shading to promote and to reduce, respectively, the storageof carbohydrates in their stems. Water-soluble carbohydrate(WSC) was extracted and separated by HPLC into glucose, fructose,sucrose, and fructan of degree of polymerization (DP) 3, 4,5, > 5, and measured in both the penultimate and fourth internodesfrom the ear to determine the effects of the manipulations. During the accumulation of WSC, the mass of fructan with a DPgreater than 5 continued to increase whilst the mass of fructansof DP 3 to 5 reached a maximum and then remained constant. Fructanaccumulated in internodes while they were extending althoughmost of the fructan in an internode accumulated after it wasfully extended. When WSC was mobilized from the stem, the massof glucose, sucrose and fructan decreased but the mass of fructosefirst increased then decreased, indicating that fructan washydrolysed at a faster rate than its product, fructose, couldbe utilized. Plants shaded to 50% of incident light from 14 d after anthesisaccumulated the same mass of WSC in the stem as controlplantsin one crop, whereas in another crop, plants shaded to 9% ofincident light from 11 d after anthesis accumulated less WSCthancontrol plants. WSC in the stem was lost from the more intenselyshaded plants earlier than from control plants. Plants de-eared at anthesis and at 21 d after anthesis accumulateda similar mass of WSC to control plants, although plants de-earedat 9 d after anthesis, in another crop, accumulated a greatermass of WSC than control plants. Although control plants mobilizedalmost all of their stored WSC, de-eared plants retained 43–55%of the WSC stored in their penultimate internode and did notlose any stored WSC from their fourth internode. In the penultimateinternodes of de-eared plants the mass of glucose, sucrose andfructan decreased and this was balanced in part by an increasein the mass of fructose. In the fourth internode, the mass ofWSC remained constant but the mass of accumulated fructose wasequal to the decrease in the mass of fructan. Results are discussed in relation to current knowledge of fructanmetabolism and to contributions of stored WSC to grainyield. Key words: Winter barley, water-soluble carbohydrate, fructan, de-earing, shading     

THE EFFECT OF GIBBERELLIC ACID ON LEAF AREA AND DRY-MATTER PRODUCTION IN MAJESTIC POTATO

When gibberellic acid (50 p.p.m. in aqueous solution) was sprayed twice or six times at weekly intervals on potato plants (var. Majestic) with a low or high nitrogen supply it did not affect rate of leaf production on the main axis, but caused earlier senescence of leaves, especially with the more frequent spraying, and inhibited leaf production and growth on laterals of the high-nitrogen plants at nodes 10 and 11 but not at other nodes. This central region of the stem appears to have a low growth potential, probably because it lies midway between two zones of active growth, viz. the basal branches and the younger leaves on the main stem. Competition between these is increased by gibberellic acid. Gibberellic acid increased leaf area even when lack of nitrogen was restricting growth but this did not produce extra dry matter. Tuber weight was increased more in high-nitrogen plants by two sprayings than by six sprayings. The net assimilation rate of low-nitrogen plants was halved by spraying but was not changed in high-nitrogen plants where the value was similar to that of low-nitrogen control plants. The high-nitrogen plants had absorbed nearly all the available nitrogen between the second and third harvests, but plants treated with gibberellic acid, nevertheless, had more total dry weight and tuber dry weight than the controls. The nitrogen content of the leaves expressed on an area basis was lower in sprayed plants and, with continued spraying, fell at the third harvest to equal that of low-nitrogen plants. Evidently, the effect of gibberellic acid depended on the interaction between the rate of application and the nitrogen supply, but further work is necessary to define the conditions that give the maximal effect on dry-matter production.     

Increased photosynthetic rates following gibberellic acid treatments to the roots of tomato plants

This study was conducted to evaluate the effects of root applications of gibberellic acid (GA₃) on photosynthesis in tomato plants grown hydroponically. Photosynthetic rates (mg CO₂/dm²/hr) determined using an open infrared CO₂ gas exchange system showed a 40–50% increase within 5 hr after treatment with a 1.4 µM gibberellic acid (GA₃) to their roots. The effect was shown to persist for the duration of the experiment (9 days). Plants receiving pulses of 1.4 µM GA₃ to the roots for 1, 4, 8 or 12 hr exhibited significantly higher photosynthetic rates than the control for 6 days following treatment. By day 9 however, there was no significant difference. Continual treatments with 1.4 µM GA₃ to the roots maintained the photosynthetic rate significantly higher than the control for the duration of the experiment. Interestingly, at the lower light levels the percent stimulation was more dramatic. There was approximately a 90% increase in the photosynthetic rate at 80 µE m^-2 s^-1 while at saturating light conditions (560 µE m^-2 s^-1) there was approximately a 40% increase over the control rate. The light saturation point for both treated and control plants was 240 µE m^-2 s^-1. Applications of physiologically relevant concentrations of GA₃ to the roots of tomato plants stimulates photosynthesis more consistently than that achieved by previous studies involving foliar absorption.Approved for publication on May 28, 1981 as paper number 6242 in the Journal series of the Pennsylvania Agricultural Experiment Station.     

Effects of growth substances on the absorption and transport of iron plants

The effects of a number of growth substances on the absorption and translocation of iron were studied in bean plants. Gibberellic acid application to the trifoliate leaf enhanced absorption of Fe applied to the primary leaf. 2-Chloroethyltrimethylammonium chloride increased absorption by the primary leaf while 6-furfurylaminopurine (kinetin) increased the transport of Fe from the primary leaf to other parts. When the roots were pretreated with gibberellic acid, the absorption of Fe by the primary leaf and subsequent transport to the trifoliate leaves were increased. Triiodobenzoic acid reduced the absorption and transport of Fe.     

Effect of the polysaccharide ofAgrobacterium radiobacter on the growth of plants and occurrence of damping-off in sugar beet

Agrobacterium radiobacter, strain B6 (a strain isolated in this laboratory, which limited the occurrence of damping-off of sugar beet and influenced growth of plants in hot-house and field experiments) was found to produce an acidic exopolysaccharide in a mineral medium with various carbon sources. Hydrolyzates of the polysaccharide contained glucose, galactose, glycerol, succinic acid and pyruvic acid, whose quantitative content varied according to the carbon source used. The polysaccharide isolated from the medium containing glucose exhibited the highest physiological activity. Seeds germinated best and sugar beet roots were found to grow most rapidly in a medium containing 0.2 % (W/W) of the polysaccharide. The roots exposed for 3 d in this medium grew 2.7-fold as compared with non-treated plants. Higher sumbers of microorganisms were detected on the surface of roots treated with the polysaccharide. Growth of roots was also stimulated when immersing the seeds (30 min) in a 0.2 –0.4 % solution of this polysaccharide. After a two-fold treatment the roots were less damaged by the fungusPythium ultimum. Plants from seeds treated with the polysaccharide grew in the field soil more rapidly than the non-treated plants but worse than after bacterization of the seeds byA. radiobacter B6 and were only partially protected against the damping-off of sugar beet.     

THE APHICIDAL ACTION OF SOME SYSTEMIC INSECTICIDES APPLIED TO SEEDS

When large seeds such as broad bean are soaked in certain systemic insecticides, notably demeton, the plants which they produce are toxic to aphids. With small seeds the effect is difficult to detect.
Experiments with demeton solutions and broad beans show that equal quantities of water and demeton are absorbed. Beans vary greatly in the rate at which they absorb solution, so, to reduce variations, about 24 hr. soaking is necessary. The insecticidal activity of the plant is directly related to the quantity of solution absorbed by the seed. Larger bean seeds absorb more solution than small beans and the plants are more toxic. After short periods of soaking (4 hr.) there is more insecticide in the seed coat than in the cotyledons, after 24 hr. there is more in the cotyledons. Some of the toxic material in the seed reaches the growing plant via the soil and roots. The material in the cotyledons can pass directly to the growing plant. As some of the material absorbed by the seed passes into the soil, any factors such as an increase in soil volume or heavy watering which tend to dilute the insecticides reduce the quantity of toxic material reaching the plant. The same quantity of demeton is more effective when absorbed by a seed than when watered on to the soil around it. Seeds soaked in insecticide, dried, and stored for one month produced plants toxic to aphids.     

The Role of Roots in Control of Bean Shoot Growth

Restriction of root growth by growing bean plants (Phaseolusvulgaris L.) in very small pots led to the development of dwarfplants. The leaves of those plants were smaller and their internodesshorter than those of control plants which were grown in largerpots and had developed a more extensive root system. A largequantity of starch—much more than in control plants —accumulated in the leaves and shoots of the dwarf plants. Increasingthe amount of minerals which was supplied to the roots, enhancedleaf growth of the control plants but failed to affect the dwarfones, in spite of the fact that in both cases the treatmentincreased the content of N, P and K in all the plant organs.The leaf water content was similar in both treatments, but theleaf water potential was higher in the dwarf plants. Exogenousapplication of gibberellic acid (GA₃) to the dwarf plants overcamethe reduction of stem growth completely, and that of the leavespartially. Application of the cytokinin, benzyladenine (BA)did not affect stem growth, but increased that of the primaryleaves. A combined supply of GA₂ + BA restored completely thegrowth of the stem and the primary leaves, and partially thatof the trifoliate leaves. It is concluded that a limited rootsystem restricts shoot growth through an hormonal system inwhich at least gibberellins and cytokinins are involved, andthat the dwarfing is not a consequence of mineral or assimilatedeficiency, or due to water stress. Phaseolus vulgaris L., leaf growth, stem growth, root restriction, gibberellic acid, benzyladenine, cytokinin     

A Study of the Absorption and Utilization of Phosphate by Young Barley Plants: I. THE EFFECT OF EXTERNAL CONCENTRATION ON THE DISTRIBUTION OF ABSORBED PHOSPHATE BETWEEN ROOTS AND SHOOTS

The effect of the external concentration on the distributionof phosphate absorbed by young barley plants was studied inexperimental periods varying from 1 hour to 7days.The experimentalwere carried out in water culture with radioactive phosphorusas a tracer. The concentration of labelled phosphate suppliedto the plants ranged from 0·0003 to over 30 p.p.m. P. When the external concentration of phosphate is reduced below10 p.p.m. P, the proportion of the absorbed phosphate foundin the shoots is markedly reduced. Plants which have been treatedwith low concentrations of phosphate lose recently absorbedphosphate to the outer medium when transferred to phosphate-freesolutions. Plants treated with higher concentrations lose asmaller proportion of recently absorbed phosphate. Different balances of other nutrients do not affect the generalrelationship between the absorption and distribution of phosphate,though quantitative changes occur.It is concluded that the retentionof phosphate in the roots induced by dilute media is a directconsequence of the small quantity of phosphate entering theroots and is not attributable to the effects of other ions whichmay be simultaneously absorbed.     

The Effect of Single and Repeated Gibberellic Acid Treatment on Internode Number and Length in Dwarf Peas

In long-term experiments comparing the results of single and repeated treatment of dwarf peas with gibberellic acid, both once-treated and weekly-treated plants formed more internodes than control plants. The initial high rate of internode formation in the once-treated peas dropped rapidly reaching that of control plants three weeks after treatment. Weekly-treated plants maintained a higher rate of internode formation. The ratio of internode lengths of once-treated plants to control plants was high (over 3) for the internodes which were elongating during or shortly after the single treatment but dropped rapidly and approached unity in later-developed internodes. The ratio of internode lengths of weekly-treated plants to control plants continued to be high throughout the experiment.     

The effect of calcium bicarbonate on iron absorption and distribution byChrysanthemum morifolium, (Ram.)

Summary Plants grown for two weeks in high-bicarbonate nutrient solution with iron became chlorotic, absorbed less iron, and translocated a lower percentage of absorbed iron than did green plants grown under low bicarbonate with iron. Chlorotic plants, pretreated in low-bicarbonate solutions lacking iron, absorbed more iron and translocated a higher percentage to leaves than the green plants. Plants induced to chlorosis by high bicarbonate absorbed less iron after transfer to low-bicarbonate solution containing iron than did chlorotic plants pretreated with low-carbonate solution lacking iron. Initial localization of iron occurred in the roots. A considerable amount of the iron initially found on the roots was translocated to developing shoots over a nine-week period unless the plants were grown in high bicarbonate solutions. More iron was translocated from roots of plants in minus-iron solutions following initial absorption than when iron was supplied in the nutrient solutions. Journal Series Paper736. University of Georgia, College of Agriculture Experiment Stations, College Station, Athens, Ga. 30601.     

THE DEVELOPMENTAL MORPHOLOGY OF NICOTIANA TABACUM ‘WHITE BURLEY’ AS INFLUENCED BY VIRUS INFECTION AND GIBBERELLIC ACID

Stein , Diana B. (U. Montana, Missoula.) The developmental morphology of Nicotiana tabacum ‘White Burley’ as influenced by virus infection and gibberellic acid. Amer. Jour. Bot. 49(5): 437–443. Illus. 1962.—‘White Burley’ tobacco with Severe Etch Virus (SEV) displayed a reduction of plant height which was overcome to a limited degree by spraying with gibberellic acid (GA). Spraying with GA, while hastening maturity in terms of earlier elongation and flowering, also prolonged the life of treated plants. Infection with SEV caused an increased rate of leaf production, and since flowering was also delayed, the greater number of leaves is produced by infected plants. Spraying with GA also increased the rate of leaf production but did not increase the final number of leaves produced. All groups except the unsprayed virus-infected plants showed a spurt in leaf production just prior to flowering. The pattern of internode elongation was obtained by the periodic measurement of individual internodes. In general, this pattern reflected the stunting properties of the virus and the growth-promoting properties of the GA. Internodes which were mature at time of spraying with GA were not affected. Infection with virus generally delayed elongation and shifted the internode pattern. Infection with SEV tended to reduce the size of leaves already present prior to inoculation, but some leaves produced after infection were actually 1arger than the same leaves on the controls. Spraying a healthy plant with GA made older leaves longer and wider, while less mature leaves at time of treatment tended to be longer and narrower. Spraying with GA reversed the reduction in size caused by the virus only if the leaf was a very young primordium or was formed during the course of treatment with GA.     

Auxin Physiology of Dwarfism in Pisum sativum

Similar levels of diffusible auxin are measured for the apices of both Little Marvel (dwarf) and Alaska (normal) cultivars of the pea when grown in sunlight and darkness. In sunlight, however, diffusible auxin disappears in the subtending internode of the Little Marvel plant but remains at 50 per cent of the level of the apex in the subtending internode of the Alaska plant. The enzyme preparation from the apex of the dwarf plant converts tryptophan and tryptamine to IAA more readily than that from the normal plant. Indoleacetyl aspartate synthetase activity is also higher in the dwarf plant than in the normal plant and the dwarf plant contains four times as much conjugate as the normal plant with or without treatment with gibberellic acid. Gibberellic acid (GA) does not affect the induction of the synthetase enzyme nor the enzymatic formation of indoleacetyl aspartate. The growth induced by GA is the result of an increased synthesis of auxin.     

Influence of gibberellic acid on <Superscript>14</Superscript>CO<Subscript>2</Subscript> metabolism,growth, and production of alkaloids in <Emphasis Type="Italic">Catharanthus roseus</Emphasis>

Changes in growth parameters, carbon assimilation efficiency, and utilization of ¹⁴CO₂ assimilate into alkaloids in plant parts were investigated at whole plant level by treatment of Catharanthus roseus with gibberellic acid (GA). Application of GA (1 000 g m⁻³) resulted in changes in leaf morphology, increase in stem elongation, leaf and internode length, plant height, and decrease in biomass content. Phenotypic changes were accompanied by decrease in contents of chlorophylls and in photosynthetic capacity. GA application resulted in higher % of total alkaloids accumulated in leaf, stem, and root. GA treatment produced negative phenotypic response in total biomass production but positive response in content of total alkaloids in leaf, stem, and roots. ¹⁴C assimilate partitioning revealed that ¹⁴C distribution in leaf, stem, and root of treated plants was higher than in untreated and variations were observed in contents of metabolites as sugars, amino acids, and organic acids. Capacity to utilize current fixed ¹⁴C derived assimilates for alkaloid production was high in leaves but low in roots of treated plants despite higher content of ¹⁴C metabolites such as sugars, amino acids, and organic acids. In spite of higher availability of metabolites, their utilization into alkaloid production is low in GA-treated roots.     

Gibberellin Substitution for the Requirement of the Cotyledons in Stem Elongation in Pisum sativum Seedlings

The removal of the cotyledons from 8-day-old light-grown Pisum sativum cv. Alaska seedlings caused a reduction in the rate of stem elongation to 50% of the intact control value. Gibberellic acid restored the stem elongation rate of decotylized plants to the level of the intact controls. The effect of decotylization was to lower both the rate of node formation and the rate of internode elongation. The steady state rate of internode elongation was reduced to 50% of the control rate by decotylization. Applied gibberellic acid did not restore the normal rate of node formation nor the lag in internode elongation caused by decotylization, but gibberellic acid did restore the normal steady state rate of internode elongation. Analysis of variance demonstrated an interaction between the cotyledons and applied gibberellic acid. 2-Isopropyl-4-dimethylamino-5-methyl phenyl-1-piperidine carboxylate methyl chloride inhibited internode elongation to the same extent in both intact and decotylized plants. The results indicate that the cotyledons are an effective source of gibberellin for the young pea seedling.     

An endogenous RNA-synthesis-promoting oligopeptide from Cucurbita pepto var. patissonina

The effect of CPPTI (Cucurbita pepo patissonina trypsin inhibitor) on the growth of Cucurbita pepo var patissonina (White bush) was examined. Plants treated with CPPTI grew faster than untreated plants and similarly to those treated with gibberellic acid. Isolated cell nuclei from plants treated with CPPTI showed that of the three DNA-dependent RNA polymerases assayed, RNA polymerase I (EC2.7.7.6) activity was preferentially elevated.Abbreviations CPPTI Cucurbita pepo patissonina trypsin inhibitor - GA₃ gibberellic acid - IAA indole-3-acetic acid - kDa kilodalton - RP I DNA-dependent RNA polymerase I     

湿度对变色秋海棠植株生长的调节作用

以变色秋海棠为材料,观测在不同空气湿度条件下栽培对植株生长的影响。结果表明:在平均湿度 75%的栽培环境,变色秋海棠的根系不太发达,茎的伸长生长明显,叶片大、质薄色浅、毛被较疏,叶柄长,以至 株高、冠幅增加;而在相对湿度60%以下略为胁迫的条件下,变色秋海棠的营养生长与上述指标对应相反。 由于相对湿度在变色秋海棠生长过程中的调节作用,导致变色秋海棠植株开展型和紧凑型两种观赏效果,可 根据需求,因地制宜采取不同的湿度调控进行栽培管理。     

Effects of drought on non-mycorrhizal and mycorrhizal maize: changes in the pools of non-structural carbohydrates, in the activities of invertase and trehalase, and in the pools of amino acids and imino acids

To study the response of non-mycorrhizal and mycorrhizal maize plants to drought, the changes in the pools of non-structural carbohydrates and amino acids were analysed in leaves and roots of two maize cvs. Plants well colonized by the arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) (60% of root length infected) and comparable non-mycorrhizal plants were subjected to moderate drought stress by reducing the water supply. This stress induced a conspicuous increase in the trehalose pool in the mycorrhizal roots, probably because it was accumulated by the fungal symbiont. Furthermore, glucose and fructose were accumulated in leaves and roots of non-mycorrhizal plants but not in the mycorrhizal ones. Starch disappeared completely from the leaves of both mycorrhizal and non-mycorrhizal plants in response to drought. Activities of soluble acid invertase and trehalase were also measured. Acid invertase activity increased during drought in the leaves of both non-mycorrhizal and mycorrhizal plants whilst in the roots it was unaffected in non-mycorrhizal plants and decreased in the mycorrhizal ones. Without drought stress, trehalase activity was considerably higher in the leaves and roots of mycorrhizal plants than in those of non-mycorrhizal plants. It increased conspicuously during drought, primarily in the leaves of non-mycorrhizal plants. A drought-induced accumulation of amino acids as well as imino acids was found in roots and leaves of both mycorrhizal and non-mycorrhizal plants; leaves of mycorrhizal plants accumulated more imino acids than those of non-mycorrhizal ones. Our results show that drought stress and the presence of a mycorrhizal fungus have a considerable effect on carbon partitioning, imino acid and amino acid accumulation in maize plants.