Young Stem Tissues Research Articles

English

Field-infected cassava stems whose leaves were identified with differential symptoms ofAfrican cassava mosaic geminivirus (ACMV) disease were assessed for index of severity of symptoms (ISS) to determine their infection status by scoring young resultant plants in the laboratory. Extracts of young stem tissues and leaves of emergent shoots from topped stems were also assayed for occurrence of ACMV by the enzyme-linked immunosorbent assay (ELISA). Geminivirus disease incidence and severity of symptoms were most abundant on leaves of plants from cuttings of field-symptomatic (I) stems of the moderately-resistant TMS 4(2)1425 (63.2%) and the susceptible TMS 60506 (51.1%) genotypes while those from apparently symptom-free (H) stems of the resistant genotype TMS 30001 recorded significantly the least disease (0%). Similarly, the index of severity of symptoms on all plants (ISSAP) and diseased plants only (ISSDP) were significantly highest on leaves of TMS 4(2)1425 (2.42 and 2.83), and were significantly the least (1) on leaves of TMS 30001, respectively. ACMV was not detected in extracts of all sections of lignified cassava stems by ELISA as all absorbance values were below threshold (0.0890). However, the virus was detected at greater concentrations in leaves of emergent axillary shoots regenerating on topped plants of all node types of TMS 60506 and TMS 4(2)1425 as well as the base (node 1) of TMS 30001 stems but not on those from middle and uppermost nodes (10 and 20, respectively) of the latter genotype. The highest absorbance values were recorded on shoots on node 1 of TMS 60506 (0.1720 ± 0.096), TMS 4(2)1425 (0.1640 ± 0.115) and TMS 30001 (0.1580 ± 0.080) in that order, while the least values were on nodes 10 (0.0298 ± 0.020) and 20 (0.0289 ± 0.019) of TMS 30001.   Key words: African cassava mosaic geminivirus, infection status, cassava genotypes, detection limitations, enzyme-linked-immunosorbent assay.

In Situ Localization of Polyisoprene in Eucommia ulmoides

The localization of polyisoprene in the young stem tissues of Eucommia ulmoides was investigated by histochemical staining and Fourier transform infrared microspectroscopy (FT-IR). The fibrous structures were stained using Oil Red O. FT-IR microspectroscopy analysis proved that the fibrous structures were indeed trans-polyisoprene. The presence of granular structures clearly stained by the dye and having a characteristic absorption at 2960 cm-1 in the FT-IR analysis suggested that trans-polyisoprene accumulated in the vicinity of the cambium layer. We have successfully demonstrated the localization of trans-polyisoprene in plant tissues for the first time, and our histological investigation has allowed us to deduce the main sites of biosynthesis and rubber accumulation.

INSECTS ASSOCIATED WITH FABA BEAN, VICIA FABA (FABALES: FABACEAE), IN SOUTHERN FLORIDA

One hundred faba bean (Vicia faba L., Fabales: Fabaceae) accessions from the USDA-NSSL Seed Repository in Prosser, WA were grown outdoors in southern Florida from December 2000 through April 2001 and October 2001 through April 2002 to both evaluate their potential as a forage crop and to initiate selections of superior genotypes. Insect herbivores and their predators were observed for feeding associations and collected for identification throughout the two seasons of trials. Sixty-one species of insect herbivores and nectaring predators and parasitoids were observed feeding on or were captured on faba bean leaves, stems, flowers, extra-floral nectaries or pods. Additionally, thirty-two species of predacious and parasitic insects were observed eating herbivorous insects or captured while searching for prey or hosts on faba beans plants. The most significant damage was caused by large populations of Aphis craccivora Koch (Hemiptera: Aphidae) that fed on terminals and young leaf and stem tissue. Six Coccinellidae species fed upon aphids and reproduced on the crop. Pods were damaged by reproducing populations of Leptoglossus phyllopus (L.) (Hemiptera: Coreidae) and Nezara viridula (L.) (Hemiptera: Pentatomidae).

Domains of expansin gene expression define growth regions in the shoot apex of tomato.

Expansins are members of a multigene family of extracellular proteins, which increase cell wall extensibility in vitro and thus are thought to be involved in cell expansion. The major significance of the presence of this large gene family may be that distinctly expressed genes can independently regulate cell expansion in place and time. Here we report on LeExp9, a new expansin gene from tomato, and compare its expression in the shoot tip with that of LeExp2 and LeExp18. LeExp18 gene is expressed in very young tissues of the tomato shoot apex and the transcript levels are upregulated in the incipient primordium. LeExp2 mRNA accumulated in more mature tissues and transcript levels correlated with cell elongation in the elongation zone. In situ hybridization experiments showed a uniform distribution of LeExp9 mRNA in submeristematic tissues. When gibberellin-deficient mutant tomatoes that lacked elongation of the internodes were treated with gibberellin, the phenotypic rescue was correlated with an increase in LeExp9 and LeExp2, but not LeExp18 levels. We propose that the three expansins define three distinct growing zones in the shoot tip. In the meristem proper, gibberellin-independent LeExp18 mediates the cell expansion that accompanies cell division. In the submeristematic zone, LeExp9 mediates cell expansion at a time that cell division comes to a halt. LeExp9 expression requires gibberellin but the hormone is not normally limiting. Finally, LeExp2 mediates cell elongation in young stem tissue. LeExp2 expression is limited by the available gibberellin. These data suggest that regulation of cell wall extensibility is controlled, at least in part, by differential regulation of expansin genes.

In-situ chemical analyses of trans-polyisoprene by histochemical staining and Fourier transform infrared microspectroscopy in a rubber-producing plant, Eucommia ulmoides Oliver.

The localization of polyisoprene in young stem tissues of Eucommia ulmoides Oliver was investigated by histochemical staining and Fourier transform infrared (FT-IR) microspectroscopy. The fibrous structures were stained with Oil Red O. FT-IR microspectroscopic analysis proved that the fibrous structures were trans-polyisoprene. Granular structures stained with the dye, and characteristic absorptions at 2,960 cm(-1) and 1,430 cm(-1) in FT-IR suggested that trans-polyisoprene accumulated in the vicinity of the cambium layer. We have thus successfully shown for the first time the localization of trans-polyisoprene in plant tissues, and our histological investigation allowed us to presume the main sites of biosynthesis and accumulation of trans-rubber. Furthermore, a new technical approach, the preparation of sections using an electronic freezing unit and the in situ analysis of polyisoprene using FT-IR microspectroscopy, is demonstrated to be a promising method for determining the accumulation of polyisoprene as well as other metabolites.

The Brassica napus extA promoter: a novel alternative promoter to CaMV 35S for directing transgene expression to young stem tissues and load bearing regions of transgenic apple trees (Malus pumila Mill.)

The Brassica napus extensin A gene is highly expressed in root tissue of oilseed rape. In an attempt to identify an effective root-specific promoter for biotechnological applications, we have examined the ability of the −940 extA promoter to drive expression of the gusA reporter gene in the vegetative tissues of apple (Malus pumila Mill cv. Greensleeves). Transgenic apple lines were produced by Agrobacterium tumefaciens-mediated transformation and GUS activity was analysed both quantitatively and qualitatively. The extA promoter was active in all tissues of young plants in all 15 clones examined. However Southern blot data suggested that only a proportion of the population contained the entire promoter and that others had suffered deletions of unknown length. This may have contributed to the variation seen in the quantitative and qualitative expression of GUS. Specific GUS activity was highest in the stems where it approached, and in some clones, exceeded that using the constitutive CaMV 35S promoter. Histochemical analysis confirmed that GUS was localised to tissues involved in structural support of the stem. Staining was particularly intense at nodal junctions where high tensile stress is exerted on the tissues. Maturing phloem tissues showed localisation of expression to the phloem parenchyma cells and phloem fibres. Transverse sections of the root revealed staining of primary procambial tissues including the young endodermis but no staining was seen in the cortex. Although the −940 extA promoter is clearly not root-specific in apple, it is likely to have useful biotechnological applications in tree species.

Purification and Molecular Analysis of an Extracellular γ-Glutamyl Hydrolase Present in Young Tissues of the Soybean Plant

A polypeptide present in intercellular wash fluids of young leaves ofGlycine maxhas been purified to electrophoretic homogeneity. The protein has been identified as γ-glutamyl hydrolase (GGH) based on the shared homology with a recently cloned cDNA from rat. The enzyme is present within the extracellular space of young leaves and a portion is bound to the cell wall. Northern and Western analysis confirm that this polypeptide is expressed only in young (1-15 d old) leaf, stem and root tissue and is therefore expressed under a strict developmental program. The primary sequence of γ-glutamyl hydrolase shares amino acid identity with a cDNA clone from rat and two partially sequenced cDNAs fromArabidopsis.Although the completein vivofunction of γ-glutamyl hydrolase in plants is unclear, it is known that the protein plays a critical role in folate metabolism and therefore likely in meeting the physiological demands of growing plant tissues.

Effects of exposure to high ozone concentrations on stilbenes in Sitka spruce ( Picea sitchensis(Bong.) Carr.) bark and on its lignification response to infection with Heterobasidion annosum(Fr.) Bref.

The resistance of Sitka spruce ( Picea sitchensis(Bong.) Carr.) stem bark tissues to the root and butt rot pathogen Heterobasidion annosum(Fr.) Bref. was reduced in trees grown for 275 days in an atmosphere supplemented with ozone (120 nmol mol -1) compared with those grown in charcoal-filtered or ambient air. Levels of the stilbene glucosides astringin and isorhapontin, the main constitutive antifungal compounds in the bark of P. sitchensiswere not altered by the ozone treatment; neither was their accumulation in young stem tissues. However, the amount of induced lignification in living bark tissues at the margin of fungal lesions was reduced in stem lengths cut from ozone treated trees, following inoculation in vitrowith H. annosum. The starch content in the xylem of these ozone fumigated trees was reduced in comparison with the other treatments. These results are discussed in relation to disease resistance and antimicrobial defence in P. sitchensis.

Expression of the rice Osgrp1 promoter-Gus reporter gene is specifically associated with cell elongation/expansion and differentiation.

To study the expression and regulation of a rice glycine-rich cell wall protein gene, Osgrp1, transgenic rice plants were regenerated that contain the Osgrp1 promoter or its 5' deletions fused with the bacterial beta-glucuronidase (GUS) reporter gene. We report here a detailed histochemical analysis of the Osgrp1-Gus expression patterns in transgenic rice plants. In roots of transgenic rice plants, GUS expression was specifically located in cell elongation and differentiation regions, and no GUS expression was detectable in the apical meristem and the mature region. In shoots, GUS activity was expressed only in young leaves or in the growing basal parts of developing leaves, and little GUS activity was expressed in mature leaves or mature parts of developing leaves. In shoot apices, GUS activity was detected only in those leaf cells which were starting to expand and differentiate, and GUS expression was not detected in the apical meristem and the young meristematic leaf primordia. GUS activity was highly expressed in the young stem tissue, particularly in the developing vascular bundles and epidermis. Thus, the expression of the Osgrp1 gene is closely associated with cell elongation/expansion during the post-mitotic cell differentiation process. The Osgrp1-Gus gene was also expressed in response to wounding and down-regulated by water-stress conditions in the elongation region of roots. Promoter deletion analysis indicates that both positive and negative mechanisms are involved in regulating the specific expression patterns. We propose a simple model for the developmental regulation of the Osgrp1 gene expression.

Structure and tissue-specific expression of genes for phenylalanine ammonia-lyase from a hybrid aspen, Populus kitakamiensis

In Populus kitakamiensis, the genes for phenylalanine ammonia-lyase (PAL) form a small gene family similar to that found in many other plant genomes. A partial cDNA clone (cDNA1) was isolated from a cDNA library constructed with mRNA from the young stem tissue of P. kitakamiensis. A genomic clone, designated pal g1 and corresponding to cDNA1, was isolated from the genomic library and characterized. pal g1 consists of two exons separated by one intron and encodes a polypeptide of 714 amino acid residues. Another genomic clone, pal g2a, was also isolated. It has one intron and encodes a polypeptide of 682 amino acid residues. Transcripts of pal g1 and pal g2a were detected by use of gene-specific probes. pal g1 mRNA was expressed in a tissue-specific manner and was detected at the highest levels in young tissues near the shoot bud. By contrast, pal g2a mRNA was mainly accumulated in mature stems and appeared not to be expressed in young tissues.

Molecular cloning and the nucleotide sequences of two novel cDNAs that encode anionic peroxidases of Populus kitakamiensis

We have cloned and characterized two novel cDNAs for peroxidases from a cDNA library constructed with mRNAs from the young stem tissue of hybrid aspen, Populus kitakamiensis. Comparison of the deduced amino acid sequences of the two cDNAs, designated pA2 and pA3, with those encoded by other known genes for peroxidases revealed several already identified regions of homology (the regions of the two His residues, the distal and proximal His residues that are bound to protoheme). Southern blot analyses indicate that pA2 and pA3 correspond to two or three genes in each class of isoenzymes. The respective transcripts of the pA2 and pA3 groups were detected by use of gene class-specific probes and it was revealed that transcripts of both groups were expressed in the lignifying tissue of P. kitakamiensis.

Gibberellin physiology of safflower: endogenous gibberellins and response to gibberellic acid

Endogenous gibberellins (GAs) were extracted from safflower (Carthamus tinctorius L.) stems and detected by capillary gas chromatography-mass spectrometry from which GA1, GA3, GA19,, GA20, GA29, and probably, GA44 were detected. The detection of these GAs suggests that the early 13-OH biosynthetic pathway is prevalent in safflower shoots. Deuterated GAs were used as internal standards and GA concentrations were determined in stems harvested at weekly intervals. GA1 and GA19 levels per stem increased but concentrations per gram dry weight decreased over time. GA20 was only detected in young stem tissue. Gibberellic acid (GA3) was also applied in field trials and both GA3 and the GA biosynthetic inhibitor, paclobutrazol, were applied in growth chamber tests. GA3 increased epidermal cell size, internode length, and increased internode cell number causing stem elongation. Conversely, paclobutrazol reduced stem height, internode and cell size, cell number and overall shoot weight. In field tests, GA3 increased total stem weight, but decreased leaf weight, flower bud number and seed yield. Thus, GA3 promoted vegetative growth at the expense of reproductive commitment. These studies collectively indicate a promotory role of GAs in the control of shoot growth in safflower, and are generally consistent with gibberellin studies of related crop plants.

Translocation of 14C-assimilates in Jerusalem Artichoke ( Helianthus tuberosus L.)

Summary When a single leaf of Jerusalem artichoke was exposed to 14CO2, labelled assimilates were primarilytransported basipetally within a limited section of the stem (about 25 % of the vascular bundles). The tubers received 14CO2 selectively indicating a high degree of continuity for the phloem from the leaves to the tubers. Speed of translocation decreased remarkably during ageing of the plant. Labelled fructans were formed in stems, stolons, tubers and roots. The stem served as a potent fructan reservoir up to preflowering stage. Sucrose was the main transport form into all parts of the plant. After flowering sucrose was directly translocated to the tubers without temporary storage in the stem. Young stem tissues gained the ability of forming fructans only gradually. On the contrary young stolons had a high capability of polymerization even before tuberization. After 14CO2- assimilation labelling of highly polymerized fructans occurred later than labelling of oligosaccharides. Polymerization capability was more pronounced in stolons and tubers than in roots and stems.

Relationship between Ureide N and N2 Fixation, Aboveground N Accumulation, Acetylene Reduction, and Nodule Mass in Greenhouse and Field Studies with Glycine max L. (Merr)

The relationship between ureide N and N(2) fixation was evaluated in greenhouse-grown soybean (Glycine max L. Merr.) and lima bean (Phaseolus lunatus L.) and in field studies with soybean. In the greenhouse, plant N accumulation from N(2) fixation in soybean and lima bean correlated with ureide N. In soybean, N(2) fixation, ureide N, acetylene reduction, and nodule mass were correlated when N(2) fixation was inhibited by applying KNO(3) solutions to the plants. The ureide-N concentrations of different plant tissues and of total plant ureide N varied according to the effectiveness of the strain of Bradyrhizobium japonicum used to inoculate plants. The ureide-N concentrations in the different plant tissues correlated with N(2) fixation. Ureide N determinations in field studies with soybean correlated with N(2) fixation, aboveground N accumulation, nodule weight, and acetylene reduction. N(2) fixation was estimated by (15)N isotope dilution with nine and ten soybean genotypes in 1979 and 1980, respectively, at the V9, R2, and R5 growth stages. In 1981, we investigated the relationship between ureide N, aboveground N accumulation, acetylene reduction, and nodule mass using four soybean genotypes harvested at the V4, V6, R2, R4, R5, and R6 growth stages. Ureide N concentrations of young stem tissues or plants or aboveground ureide N content of the four soybean genotypes varied throughout growth correlating with acetylene reduction, nodule mass, and aboveground N accumulation. The ureide-N concentrations of young stem tissues or plants or aboveground ureide-N content in three soybean genotypes varied across inoculation treatments of 14 and 13 strains of Bradyrhizobium japonicum in 1981 and 1982, respectively, and correlated with nodule mass and acetylene reduction. In the greenhouse, results correlating nodule mass with N(2) fixation and ureide N across strains were variable. Acetylene reduction in soybean across host-strain combinations did not correlate with N(2) fixation and ureide N. N(2) fixation, ureide N, acetylene reduction, and nodule mass correlated across inoculation treatments with strains of Bradyrhizobium spp. varying in effectiveness on lima beans. Our data indicate that ureide-N determinations may be used as an additional method to acetylene reduction in studies of the physiology of N(2) fixation in soybean. Ureide-N measurements also may be useful to rank strains of B. japonicum for effectiveness of N(2) fixation.

Solutes in the Free Space of Growing Stem Tissues

The concentration of osmotically active solutes in the cell wall free space of young stem tissues was studied using a variety of extraction methods. When the intercellular air spaces of etiolated pea (Pisum sativum L.) internodes were perfused with distilled H(2)O, the resulting solution contained a solute concentration of about 70 milliosmoles per kilogram. A second procedure involving vacuum infiltration of segments followed by centrifugation to collect the free space solution gave similar results. Apical stem segments yielded free space extracts about twice as concentrated as those from basal portions of the stem. After correcting for dilution of the free space solution by the infiltrated water, the osmotic pressure of the undiluted free space in pea stem tissue was estimated to be 2.9 bars for apical segments, 1.8 bars for basal regions. These values may be somewhat overestimated due to solute efflux from intracellular pools during the extraction procedure. Similar results were obtained for stem regions of etiolated soybean (Glycine max [L.] Merr.) and cucumber (Cucumis sativus L.) seedlings.From measurements of the electrical conductivity and refractive index of free space extracts before and after ashing, it appears that 25% of the solutes are inorganic electrolytes and 75% are organic nonelectrolytes with an average size similar to that of glucose.A significant osmotic pressure in the wall space offers an explanation for the frequent observation that nontranspiring plants have negative water potentials. Calculations of hydraulic resistance from water potential data must take into account solutes in the free space, else ;apparent,' but unreal, changes in resistance may be calculated.

Critical Ca Levels and Ca/Mg Ratios in Trifolium subterraneum L. Grown on Serpentine Soil1

AbstractSerpentine soils are known to have a low Ca/Mg ratio and to respond to applied Ca in many instances. To assist in assaying the Ca status of these soils we determined the effect of growth stage, plant part, and defoliation treatment on the critical Ca concentrations and Ca/Mg ratios in subclover growing in potted serpentine soil of the Henneke series, a lithic Argixeroll.One of six rates (0, 200, 400, 800, 1,600, and 3,200 ppm) of Ca as CaSO4 and uniform rates of P, K, S, and Mo were applied to each pot and the soil was mixed uniformly and planted to ‘Geraldton’ subclover (Trifolium subterraneum L.). On one set, leaves were removed 61, 85, and 114 days after planting. On a second set, leaves were removed on days 85 and 114, and the third set grew without clipping until day 114.Critical Ca percentages in the three youngest leaves ranged from 0.55 to 0.69%, with no consistent trend due to growth stage or number of times the plant had been defoliated. In old leaves, critical Ca levels ranged from 0.81 to 1.47% and were higher for 114‐day‐old plants than for 85‐day‐old plants. The more often the plant was defoliated the lower the critical Ca level in old leaves. There was no significant difference between young and old stem tissue in critical Ca levels: 0.30 to 0.38% Ca. Defoliation did not induce a consistent change.Critical Ca/Mg ratios in young leaves increased from 0.42 to 0.60 between plant ages of 61 and 85 days, whereas no significant change occurred from day 85 to 114. With plants defoliated for the third time at day 114 the critical Ca/Mg ratio was 0.36, although at the first and second clippings their critical ratios were 0.60. Calcium/Mg ratios were similar in young and old leaves. In young stems the critical Ca/Mg ratios on day 114 for the first, second, and third clippings were respectively 0.48, 0.39, and 0.21. The same values for old stem tissue were 0.38, 0.27, and 0.18.It was concluded that percent Ca and Ca/Mg ratios in new and old stems were insensitive as measures of Ca status since these values changed less in stem than in leaves over a wide range of Ca levels. Percent Ca in young leaves was the best measure of Ca status because critical values varied less due to stage of growth or clipping treatment than did percent Ca in old leaves or Ca/Mg ratios in young or old leaves.

Low temperature induced metabolic changes in the shoot meristematic region of Marquillo × Kenya Farmer wheat dwarf 1 plants

Marquillo × Kenya Farmer 1 (Mql × KF 1) wheat plants respond to very short 16° treatment by decreased meristematic activity of the apical meristem and extensive cellular destruction in young leaf and stem tissues. By radiotracer techniques the metabolism of 3H-thymidine, 32P, and 14C-leucine fed to intact shoot tissues of Mql × KF 1 and normal Marquillo (Mql) plants were studied.Immediately after the onset of 16° treatment, the incorporation of both 3H-thymidine and 32P into the DNA of Mql × KF 1 meristematic regions began to decline rapidly although the total uptake of label into the meristematic tissue remained constant. The incorporation of 32P into the RNA, the acid-soluble organic phosphate compounds, and phospholipids of the Mql × KF 1 meristems also declined during the first 24 h and the inorganic phosphate radioactivity increased. After the initial decrease, the proportion of radioactivity in the RNA and acid-soluble organic compounds increased to near control levels. The distribution patterns of both 3H-thymidine and 32P were unchanged in the meristematic region of Mql × KF 1 plants at 26° or Mql plants at 16° or 26°. Protein synthesis in meristematic regions, measured by the incorporation of 14C-leucine, responds to temperature similarly in Mql × KF 1 and Mql plants.The inhibitions of mitosis, phospholipid synthesis, and DNA synthesis were extremely rapid and reversible after short 16° exposures, and are thought to be close to the primary process of temperature lethality of Mql × KF 1 plants. Although it is not known if any of these processes are responsible for the others, it is proposed that the cellular destruction is caused by the inability of cells in the elongating regions to synthesize the phospholipid components of membranes.

The Effect of 2,4-Dichlorophenoxyacetic Acid on the Respiration of Etiolated Pea Seedlings.

Since the report of Brown (6) that 2,4-dichlorophenoxyacetic acid (2,4-D) increased the rate of carbon dioxide production from intact bean plants, many reports on the influence of 2,4-D on respiration have appeared in the literature. Smith (14) and Avery (1) have reviewed the literature which appeared before 1950. Some of the more recent papers are listed in the Literature Cited section of this paper (7, 8, 12, 17, 18). French and Beevers (7) suggest that the increase in respiration induced by 2,4-D, indoleacetic acid (IAA), and other plant growth substances is a result of the increase in growth induced by these substances. An increase in growth with an attendant increase in anabolic reactions would increase the supply of high energy phosphate acceptors, and thus, presumably, increase the rate of respiration. This suggestion was based, in part, on the findings that these plant growth substances, in the concentration range that increased the elongation of corn coleoptile segments, increased the respiration of the segments, while 2,4-dinitrophenol, which inhibited growth, also caused a marked increase in the rate of respiration. The work of Kelly and Avery (12) lends support to this interpretation. These workers found that, although the respiration of young pea stem tissue was markedly stimulated by 2,4-D, the respiration of tissue slices from older pea stem segments which had ceased to elongate was not increased by 2,4-D. Bonner and Bandurski (4), in their discussion of the action of IAA on respiration and growth, are inclined to a view similar to that of French and Beevers (7). This paper reports the results of an investigation on the phenomenon of respiratory stimulation by 2,4-D with respect to the qualitative and quantitative changes in the respiratory substrate. It is postulated that 2,4-D increases respiration by causing more glucose to be catabolized via the pentose phosphate path-

Sunflower Stem Cultures for the Detection of Plant Hormones

FRAGMENTS of young stem tissue of Helianthus annuus (L.), when cultured on a nutrient medium containing 2 per cent sucrose and mineral salts, are capable of making only a limited amount of growth, chiefly confined to the production of a pad of callus tissue on the cut surface. Such cultures have been shown to respond in various ways to certain plant hormones. Root production results from the addition to the medium of one part per thousand million of such substances as indole acetic, indole butyric or naphthalene acetic acid to the agar on which such stem fragments are cultured. The type of root growth varies with the hormone used1. Higher concentrations of these substances cause a characteristic proliferation of the stem tissue. These reactions have already been used to demonstrate the presence of indole acetic acid in commercial penicillin. The crystalline penicillins G and X were shown to have root-initiating properties by this means, but to differ from indole acetic acid in that they failed to induce the same characteristic cellular proliferation at high concentration2. The reactions have also led to the detection of growth-substances in bacteria-free crown gall tissue.