Chloramphenicol effects on adventitious root production by radish hypocotyls

Abstract

The excision of the root accelerates greatly the formation of adventitious roots in the hypocotyl of etiolated radish seedlings, but if the seedlings develop in CAP 1×10^?4M, no adventitious root are induced after cutting. IAA either alone or associated with CAP, significantly increases the number of primordia in normal hypocotyls if given at the moment of cutting, while it has not stimulatory effect on the hypocotyls of seedlings grown in CAP. IAA has significant effect on both elongation and tickening of hypocotyl segments prepared from seedlings grown in CAP, and this could indicate a specific action of the inhibitor either on a particular process or on particular cells.

The endodermis and the pericycle, which are the two cell layers implicated in the formation of the adventitious roots, could be the mediators of this particular effect of CAP in rooting.     

Stimulation of insulin release by L-glutamine

Summary Under normal environmental conditions, L-glutamine is well oxidized but fails to stimulate insulin release in rat pancreatic islets. However, a marked stimulation of insulin release by L-glutamine, without alteration in its oxidation rate, occurs when the intracellular pH of the islet cells is decreased and/or when theophylline is added to the incubation medium.     

Studies on the effect of certain enzymic poisons on the metabolism of storage organs III. Uptake and utilization of sucrose by radish root slices in presence of iodoacetate

Iodoacetate greatly retarded the uptake of sucrose and slightlyaffected its inversion by radish root slices. Carbohydrate content of the samples decreased substantiallyboth in water and in iodoacetate. Feeding with sucrose led tomarked accumulation of carbohydrates and supplemental additionof iodoacetate induced less accumulation of carbohydrates. Iodoacetate caused exudation of nitrogen fractions into theculture media. Protein synthesis via amino acids seems to beoperative in iodoacetate treated slices. It is also suggestedthat nitrate-N, in presence of sucrose, is converted into peptidesand proteins. Addition of iodoacetate to sucrose media inhibitedthis pathway of protein synthesis. Both sucrose and iodoacetate (4 x 10^–4M) stimulated theCO₂ output whereas 25 x 10^–4M iodoacetate did not changethe CO₂ output when compared with that of controls. Sucroseand iodoacetate (4 x 10^–4 M) when joined together maskedthe accelerating effect of each other. ¹Present address: Department of Botany, Faculty of Science,University of A'in Shams, Abbassia, Cairo, Egypt, U. A. R. (Received November 6, 1968; )     

Regulation of salt respiration in carrot root slices

In slices of carrot-phloem parenchyma washed for 7 days in water at 20 C, 50 mm KCl stimulates respiration by up to 100% of the ground respiration within 4 minutes of application. The data presented imply that ADP liberated in the cytoplasm as a consequence of KCl accumulation first stimulates a regulator reaction requiring ADP (phosphoglycerate kinase). Thereafter, the point of control alternates between this reaction and the phosphofructokinase reaction, forming a sequence of enzyme stimulations which continue after the new steady state of increased respiration is established. KCl induces a similar sequence in slices washed for 3 days, but it is completed within 3 minutes, and metabolite oscillations are not so marked. In slices washed for 2 days, KCl stimulates respiration by less than 10%, and the sequence of regulator reactions does not occur. Phosphoglycerate kinase is the only enzyme stimulated within 3 minutes of applying KCl to these slices. Contrary to previous reports, KCl frequently stimulates the respiration of freshly prepared slices by 10 to 30%.     

Studies on the effect of certain enzymic poisons on the metabolism of storage organs IV. Respiration and nitrogen assimilation by radish root slices in relation to feeding with KCN

At low and high concentrations, respectively, KCN stimulatedand inhibited the CO₂ output of radish root slices. Analysisof tissue slices showed that CO₂ production is nearly accountedfor by the loss in carbohydrates. After 48 hr, the content ofprotein-N was slightly changed in all the cyanide-treated tissues;whereas, that of soluble-N decreased markedly at high cyanideconcentrations and hardly changed at low concentrations. Leakageof soluble-N occurred at high concentrations of cyanide. The nitrogen compounds taken up were incorporated into the nitrogenpool of radish slices. KCN retarded uptake of nitrogen compounds,inhibited their utilization and led to excessive leakage ofsoluble-N from the tissues into the media. Increased CO₂ outputof slices in nitrogen media was largely accounted for by theloss in carbohydrates from the tissues. High concentrations of cyanide are thought to inhibit CO₂ outputthrough inhibition of the oxidase system and accompanying phosphorylations.The present results with low concentrations further substantiatethe uncoupling theory as a main factor involved in respiration. ¹Permanent address: Department of Botany, Faculty of Science,University of A'in Shams, Abbassia, Cairo, Egypt, U.A.R. (Received October 3, 1969; )     

The organization of cortical microtubule arrays in the radish root hair

Summary Cortical microtubule arrays in the radish root hair were analyzed from reconstructions of serial ultra-thin sections in order to test extant hypotheses concerning the role of microtubules in the deposition of oriented microfibrils of cellulose. Passing away from the tip, root hairs exhibit a transition from random to oriented deposition of microfibrils at approximately 25 m. Along the root hair, passing back from the tip, the microtubules: a) increase in number to a plateau at 25 m; b) change their length profiles from approximately 60% less than 1 m long in the hair tip to approximately 40% less than 1 m long at 60 m; c) maintain a constant pattern of angular deviation from the long axis, which is similar to the deviation pattern of the oriented wall fibrils; d) maintain a constant (approximately 70% of tubules) close (within 50 nm) proximity to the plasma membrane (PM); e) maintain a low (approximately 20%) degree of inter-microtubule proximity (i.e., within 50 nm of one another); f) show evidence for some variable long range (>50 nm) association. Fixation with glutaraldehyde in a complete microtubule polymerization medium (MTPM), or pretreatment with cytochalasin B cause an approximate twofold increase in 1. the proportion of long microtubules in the tip region and 2. microtubules within 50 nm of one another. Fixation in incomplete MTPM (without GTP) produces results similar to phosphate buffer controls. Alternative explanations for these results are examined. A new hypothesis accounting for microtubule involvement in oriented microfibril deposition is described.     

Laboratory studies of non-preference resistance to cabbage root fly in radish

First generation progenies selected from four radish cultivars on the basis of their attractiveness to ovipositing cabbage root fly in the laboratory were compared in the same environment. There were significant differences between and within cultivars in their attractiveness for egg-laying, indicating that genetic variation existed and that selection had effected a heritable change. However, inconsistencies between experiments indicated that other, as yet unquantified, factors were compounded with the heritable component of non-preference resistance. There was no evidence to suggest that seed weight, leaf area, or hypocotyl size affected the attractiveness of the plants. The effects of eliminating any choice between selections was investigated in the laboratory by exposing 4-wk-old ‘high’ and ‘low’ preference selections of cv. Asmer Tip Top to the pest for 6 days. Three times as many eggs were laid on ‘high’ than on ‘low’ preference selections, indicating that the heritable non-preference resistance to cabbage root fly in Asmer Tip Top was maintained when no choice was offered to the flies, an essential requirement for ‘resistant’ cultivars in the field.     

Coated vesicles and other cytoplasmic components of growing root hairs of radish

Summary Root tips of radish,Raphanus sativus, were fixed in glutaraldehyde followed by osmium tetroxide. The fine structure of young root hairs, not exceeding about 130, in length, was studied to relate their apical growth pattern to their cytoplasmic organization. The cytoplasm in the terminal 3–5 it of the root hair is characterized by an electron dense matrix in which lie numerous smooth-surfaced vesicles, large irregularly-shaped fibrous inclusions, and clusters of ribosomes. Other organelles are largely or entirely excluded from this region. Farther than about 5, from the tip, the hair cytoplasm is filled with plastids, rough endoplasmic reticulum, mitochondria, and dictyosomes. The latter produce smooth vesicles similar in size and morphology to those present in the apical dome. Vesicles of a different kind appear in the peripheral cytoplasm along the entire length of the hair. These vesicles possess an alveolate or chambered coat about 20 m thick and have a diameter of about 85 m, including coat. They originate by evagination from the large, smooth-surfaced vesicles in the vicinity of dictyosomes. It is suggested that proteins and carbohydrates are concentrated in the dictyosomes and then segregated in the smooth vesicles released from the dictyosome cisternae. The coated vesicles which bud from the smooth vesicles may serve to isolate the proteins and transport them to the hair surface for participation in wall synthesis. The smooth vesicles are believed to convey carbohydrates to the region of active wall extension at the hair apex.This work was supported in part by grant GM-10493 from the National Institutes of Health. United States Public Health Service, to Dr. H. T. Bonnett, Jr., and grant RG-628 from the National Science Foundation to Dr. E. H. Newcomb.     

Effect of exogenous hydrogen peroxide on biophoton emission from radish root cells

Biophotons spontaneously emitted from radish root cells were detected using highly sensitive photomultiplier tube. Freshly isolated radish root cells exhibited spontaneous photon emission of about 4 counts s^?1. Addition of hydrogen peroxide to the cells caused significant enhancement in biophoton emission to about 500 counts s^?1. Removal of molecular oxygen using glucose/glucose oxidase system and scavengering of reactive oxygen species by reducing agents such are sodium ascorbate and cysteine completely diminished biophoton emission. Spectral analysis of the hydrogen peroxide-induced biophoton emission indicates that biophotons are emitted mainly in green–red region of the spectra. The data provided by electron paramagnetic resonance spin-trapping technique showed that formation of singlet oxygen observed after addition of H₂O₂ correlates with enhancement in biophoton emission. These observations provide direct evidence that singlet oxygen is involved in biophoton emission from radish root cells.     

Phenolic metabolism in root slices of selected carrot cultivars

Carrot root slices, stored for 4 days at 20 °C reacted with a strong accumulation of total phenols, especially chlorogenic acid. A significant accumulation of isocoumarin content within the peel was observed in stored slices. Synthesis of phenols was accompanied by an increase in phenylalanine ammonia lyase activity, wound induced respiration and ethylene production. The great variability among the studied four cultivars was found concerning isocoumarin synthesis, PAL activity, respiration rate and ethylene evolution, but less distinct in the case of chlorogenic acid accumulation. The carrot slices obtained from freshly harvested roots were more sensitive to mechanical damage and short-term storage than those prepared from roots previously stored.     

Influence of formulation on chlorfenvinphos uptake and cabbage root fly control on radish

Granular and liquid formulations of chlorfenvinphos were applied to a sandy-loam as continuous logarithmically-changing doses of approximately 0.2 to 4.0 kg a.i./ha and radish were sown immediately and 23 days after treatment. After 62 days, insecticide concentrations in the soil had not diminished detectably in the granule treatment but had declined by about 20% in the liquid treatment. In both sowings, residues in the harvested radish were higher, dose-for-dose, from the granule than from the liquid treatment and with both formulations were lower in the second than in the first sowing. Within treatments there were log-log relationships between the dose of insecticide and residue concentrations in the soil and radish. In both sowings the residues were most variable between replicate soil and crop samples from the granule treatment. In the first sowing, cabbage root fly damage was reduced most by the liquid treatment but in the second sowing equivalent doses of the two formulations gave similar protection. At 2.0, 2.24 or 3.0 kg a.i./ha, chlorfenvinphos incorporated before sowing protected radish better than pre-sowing or pre-emergence applications to the soil surface. When applied before sowing, the liquid formulation gave better protection and lower residue concentrations in the radish than the granules. As a post-emergence spray, chlorfenvinphos was much more effective than fonofos, diazinon or triazophos but it was often phytotoxic, decreased yield significantly, left large residues in the radish in two of the four experiments and, in common with other surface treatments, substantially decreased the Z:E chlorfenvinphos isomer ratio. Although a single application of granules protected two successive radish crops, it was concluded that third and subsequent sowings on the same land should probably be treated with smaller doses to limit terminal residues.     

Adventitious root induction inCorylus avellana L. cotyledon slices

Summary An experimental rooting system was developed to study in vitro adventitious root formation in hazelnut cotyledons. Experiments involveda) assay of several culture media,b) use of different developmental status of the seeds (germinated and ungerminated),c) cotyledons subjected to various light regimes, andd) different size of cotyledons slices. It was observed that higher rooting was induced in cotyledonary portions of 5- or 7-mm thickness (250 and 350 mm³, respectively) cultured on half-strength basal medium supplemented with 50 μM indole-3-butyric acid and 5 μM kinetin. Rooting was affected by light and the developmental state of seeds. Preinitiation, initiation, and root manifestation stages were defined according to specific culture periods and in relation with morphologic and histologic changes. The first histologic changes (cell division and root primordia induction) were observed after 12 days in culture. At 30 days of culture in rhizogenic medium root primodia were fully differentiated with well-developed vascular tissues.     

On the utilization of L-glutamine by glutamate dehydrogenase.

The action of glutamate dehydrogenase on L-glutamine was followed by determining the formation of α-ketoglutaramate. The rate of the reaction with L-glutamine was about 0.01% of that observed with L-glutamate. The findings suggest that α-ketoglutaramate present in tissues arises mainly by transamination rather than by oxidation of glutamine. tamine. Glutamate dehydrogenase does not catalyze glutamate formation from α-ketoglutarate and L-glutamine at a significant rate, but the present findings do not exclude the possibility that glutamine amide nitrogen is used for synthesis of α-amino groups in the mammal by pathways involving coupling between glutamate dehydrogenase and glutaminase (or $\text{Ω-amidase}$) or a glutamine-binding subunit, i.e., by reactions equivalent to that catalyzed by glutamate synthase.     

Induction of primary root curvature in radish seedlings in a static magnetic field

Primary roots of radish (Raphanus sativus L.) seedlings were exposed to an inhomogeneous static magnetic field generated by a permanent magnet, during continuous rotation on a 0.06 rpm clinostat, thereby reducing the unilateral influence of gravity. The roots responded tropically to the static magnetic field with the tropism appearing to be negative. These roots responded significantly (P < 0.05) to the south pole of the magnet. The significant tropic response was found for a magnetic flux density of 13-68 mT, for a field gradient of 1.8-14.7 T/m, and for the product of magnetic field and field gradient of 0.023-1.0 T(2)/m. A small, but insignificant, response of the roots to the north pole has also been found.     

Utilization of L-alanine and L-glutamine by lactating mammary gland of the rat. A role for L-alanine as a lipogenic precursor.

1. Lactation is associated with an increase in the arterial blood concentration of L-alanine and L-glutamate, but a decrease in that of L-glutamine compared with the corresponding values for virgin rats. 2. Virgin rats fed a 'cafeteria diet' that induces hyperphagia have increased arterial concentrations of L-alanine, L-glutamate and L-glutamine. During lactation L-alanine and L-glutamate concentrations are even higher. 3. The removal of L-alanine is decreased in hepatocytes from lactating rats fed either a chow or cafeteria diet. 4. Measurements of arteriovenous differences across lactating mammary glands indicate that appreciable amounts of L-glutamine and L-alanine are extracted by the gland. 5. A high proportion of the L-alanine metabolized by isolated acini from fed lactating rats is converted into lipid. 6. Metabolism of L-alanine in acini from starved lactating rats is limited by the activity of pyruvate dehydrogenase. 7. It is concluded that L-alanine and certain other amino acids taken up by the gland in excess of the requirements for protein synthesis can be converted into lipid.     

The influence of plant age on resistance of radish to cabbage root fly egg-laying

Cabbage root fly ( Delia brassicae ) egg-laying around radish plants ranging in age from newly emerged seedlings to plants with flowering shoots was studied in the field and laboratory. The attractiveness of radish changed with age, one peak in egg-laying occurring just before plants were of marketable size and further peaks as they produced flowering shoots. The pattern of egg-laying was similar for the six radish cultivars tested, both in the field and laboratory, irrespective of whether flies did or did not have a choice of plants of different ages. At any one age, there was no correlation between egg-laying and plant size. Selection within radish cultivars for the extremes of the range of egg-laying preference appeared to alter the cycle of attractiveness of different radish stocks to cabbage root fly, the response being influenced by environmental conditions.     

CDNA cloning of radish (Raphanus sativus) myrosinase and tissue-specific expression in root

Two cDNA clones of myrosinase (thioglucoside glucohydrolase, EC 3.2.3.1) were isolated from radish (Raphanus sativus) seedlings. Both clones were identified as MB (B type myrosinase) from their sequence homology at the amino acid level to MBs cloned from other Brassicaceae species. The tissue distribution of gene expression and enzyme activity of myrosinase corresponded well to the site of glucosinolate accumulation in different tissues of radish. The myrosinase-glucosinolate system was localized in the cotyledons in the seedlings and in the peel of the root in the mature plant. Tissue printing analysis showed that myrosinase mRNA and activity were localized in the epidermis and vascular cambium that were present in the peripheral part of the root but few signals were detected in the parenchyma inside of the vascular cambium. Since the myrosinase-glucosinolate system is known to be a defense system in higher plants, the localization of the myrosinase-glucosinolate system in the peel of the root may act to protect the sink organ from the attack of herbivores or pathogens in soil.