EFFECT OF GIBBERELLIC ACID ON THE GROWTH AND ANATOMY OF COLEUS BLUMEI, ANTIRRHINUM MAJUS AND SALVIA SPLENDENS

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1 New Phytol. (1967) 66, EFFECT OF GIBBERELLIC ACID ON THE GROWTH AND ANATOMY OF COLEUS BLUMEI, ANTIRRHINUM MAJUS AND SALVIA SPLENDENS BY JACK M. BOSTRACK* AND B. ESTHER STRUCKMEYER Department of Horticulture, Lnirersitx of Wisconsin, Madison {Received 21 March 1967) SUMMARY Plants of Coleus bluniei (Coleus), Antirrhinum majus (snapdragon) and Sahia splendens (Salvia) exhibited three common responses to foliar applications of 50 mg/1 aqueous solution of gibherellic acid (GA); elongation of the internodes, hyponasty and chlorosis. Elongation of subapical internodes was a result primarily of cell division in both Antirrhinum majus and Sahia splendens. Gibberellic acid at 500 mg/1 caused less elongation of the sub-apical region than at 50 mg/1 and 100 mg/1 in S. splendens. Treated plants had a smaller stem diameter and more xylem parenchyma. Coleus bluniei cuttings showed reduced rooting when treated with 50 nig/l GA. INTRODUCTION Application of gibberellic acid (GA) to plants, results in a variety of responses. The elongation of internodes has been reported to be a result of cell division (Sachs, Bretz and Lang, 1959; Greulach and Haesloop, 1958), cell elongation (Kato, 1955; Brian, 1958) or both (Dure and Jensen, 1957; Cooper, 1958; Bradley and Crane, 1957). Treated plants exhibited a change in leaf shape or size (Brian and Grove, 1957; Soost, 1959; Gray, 1957) and a retardation of root growth (Kato, 1958). The results of this investigation are intended to add to the information concerning the effects of GA on plant growth and anatomy. MATERIALS AND METHODS Rooted cuttings of Coleus bluniei and Salvia splendens, and seedlings of Antirrhinum majus were grown in the glasshouse at a temperature of approximately 65' F. Gibberellic acid was applied as an aqueous foliar spray, three times a week at concentrations of 50, ioc and 500 mg/1. Plants sprayed with distilled water served as controls. Tissues selected for anatomical examination were sampled and processed according to standard microtechniques (Sass, 1958). RESULTS Effects of GA on shoot apical meristems All GA-treated plants exhibited elongation of internodes. Shoot apices of Antirrhinum majus showed no change in size, shape or organization as a result of treatment w ith 50 mg/1 of GA. Early elongation of the sub-apical internodes occurred in treated plants * Present address: Biology Department, Wisconsin State University, River Falls, Wisconsin. 539

2 S40 JACK M. BOSTRACK AND B. ESTHER STRUCKMEYER (Plate 27, Xos. I and 2) as a result of an increased rate of cell division which accounted for few er leaf primordia within the terminal bud (Plate 27, Nos. 3 and 4). The average number of leaf primordia in the terminal bud of untreated and treated plants was 6.5 and 4.0 respectively. Plants of the d\\ arf, indeterminate, variety of Salvia, 'St. John's Fire', were grown in lung days and treated with 50, 100 and 500 mg/1. GA. After 20 days the plants treated \\\Xh 100 mg/1 GA were nearly twice the height of the untreated ones. Plants treated with ^00 mg/i GA were not as tall as those treated with 100 mg/1. Plants of both treatment groups exhibited greater elongation of sub-apical internodes than the untreated ones. However, the elongation of internodes occurred to a greater extent in plants receiving 100 mg/1 GX (Plate 2S, Xos. 8 and 9). Measurements of pith parenchyma cells revealed that the elongation of the sub-apical internodes was a result of an increase in the rate of cell division. Treated Coleus bhimei plants showed a similar elongation of internodes, although the response was not as conspicuous as the other species. Effects of GA on stem anatomv Transverse sections of stems sho\\ed the diameter of Antirrhinum majtis plants treated with :^o mg/1 GA to be considerably less than untreated ones. The cells of the fourth internode from the terminal bud were smaller in diameter, particularly in the pith and cortex (Plate 27, Nos. 5 and 6). Inaddition, GA stimulated the differentiation of xylem parenchyma. Some axillary shoots of A. majiis plants near the growing point, treated for an extended period of time, showed a gradual weakening and degeneration of tissue. When maximum degeneration of tissue had occurred, the growing points of the axillary shoots hung in a pendant fashion (Plate 27, Xo. 7), and the supporting, degenerated stem tissue had become white and flaccid. The degeneration did not inhibit conduction of materials acropetally, because the growing point and young leaves continued growth until the experiment was terminated. Although the tissue immediately below the growing point had collapsed, the apex continued to grow, produce leaves and respond negatively to gravity. The degeneration of cells occurred in the cortex, phloem and vascular cambium. In advanced stages all of the tissues were obliterated except the vessels. Cuttings of Coleus bltnnei were treated with GA; one group was placed in distilled water and the second group was grown in a 50 mg/1 solution of GA. Eleven days after treatment the stimulation of the vascular cambium was apparent by the production of xylem parenchyma. This reaction was more pronounced 26 days after treatment (Plate 28, Xos. 10 and 11). Production of xylem parenchyma was observed also in treated Salvia sptendens plants. Effects of GA on leaf grotvtli All three species of plants exhibited a hyponastic response to foliar application of a 50 mg/1 concentration of GA. Examination of the petiole base of Coleus blumei showed the hyponastic response was caused by an increase in cell elongation on the lower side of the petiole. Higher concentrations of GA induced opposite effects. Salvia splendens exhibited an epinastic response to 100 mg/1 and 500 mg/1 GA. Gibberellic acid induced a change in the shape of leaves. The lamina of treated plants of S. splendens and Coleus blumei were narrower, longer, more acuminate and exhibited

Effect of gibberellic acid on Coleus, etc. 541 undulated surfaces compared to the untreated. The leaves of treated Antirrliinuni iiiajns were narrower and shorter than those on untreated plants.

3 Effect of gibberellic acid on Coleus, etc. 541 undulated surfaces compared to the untreated. The leaves of treated Antirrliinuni iiiajns were narrower and shorter than those on untreated plants. The mature lamina of treated and untreated plants revealed no significant microscopic anatomical differences. Effects of GA on rooting oj Coleus blumei cuttings Foliar applications of 50 mg/1 GA did not inhibit the formation of roots on C. bhnnei cuttings. Studies were made to determine if GA would be more effective in inhibiting root initiation and growth if the cuttmgs were immersed directly in a 50 mg/1 solution of GA. Twenty-five uniform cuttings were grown in five fiasks covered with brown paper. Two flasks of five cuttings each contained distilled water; one was sprayed twice a week with GA. Similarity, two flasks of five cuttings each, one treated and one not, contained Hoagland's nutrient solution (Hoagland and Arnon, 193S). The fifth flask of fi\ e cuttings contained 50 mg/1 solution of GA. Nine days later, treated and untreated cuttings grown in distilled water and Hoagland's solution showed profuse root formation and growth. Cuttings grown immersed in the GA solution only had root primordia protruding through the epidermis. The effects of the various treatments on the growth of roots after 33 days is shown in Plate 28, No. 12. The treated and untreated cuttings grown in Hoagland's nutrient solution had the greatest number of roots; those grown in distilled water had the next greatest and the least number of roots developed on cuttings grown in the solution of GA. DISCUSSION Recent work on the shoot apical meristem of Hyoscyamus niger and Samolus parz-iforus treated with GA (Sachs et al., 1959) revealed that cell activity of the sub-apical region, immediately below the apical meristem, was largely responsible for the elongation of the plant axis as a result of cell division. Eighty per cent of the GA-induced cell divisions were anticlinal, which contributed to the extension of the plant axis. Greulach and Haesloop (1958) also found that applications of GA resulted in elongation of internodes oi Phaseohis vulgaris and concluded that this was chiefly the result of increase in the rate of cell division. Arney and MancinelH (1966) reported that the effect of GA treatment varies with the tissue and the stage of maturation of cells. They found no evidence of premature cell enlargement. Measurements of stem pith cells in the subapical region of Salvia splendens and Antirrhinum majiis in this investigation are in accord with the findings of Arney and Mancinelli (1966). Haber and Luippold (i960) related that cell division alone cannot result in increased growth of tissue, because the division of one cell into two, each one-half the size of the parent cell, will not result in enlargement. Cell expansion after cell division is necessary for normal growth. Roller, Highkin and Caso (i960) reported that the basal internodes in certain vernalizable grasses elongated after treatment with GA. However, GA did not promote the elongation of the sub-apical internodes. Numerous conflicting reports in the literature suggest that several factors may influence the response of plants to GA, such as inherent differences in plants, the concentration of GA applied, the stage of maturation at the time of treatment and environmental conditions.

542 JACK M. BOSTRACK AND B. ESTHER STRUCKMEYER Associated with internode elongation was a smaller stem diameter reported earlier bv Brian et al. (1954) and Bostrack and Struckmeyer (1964).

4 542 JACK M. BOSTRACK AND B. ESTHER STRUCKMEYER Associated with internode elongation was a smaller stem diameter reported earlier bv Brian et al. (1954) and Bostrack and Struckmeyer (1964). The three species of plants in this investigation showed a reduction in stem diameter. This response appears to be common in dicots, but may not be the case for monocots (Cherry, Lund and Earlev, i960). In certain species GA induced increased cambial activity. Wareing (1958) observed that the cambium of seedlings of Acer pseudoplatanus, cut shoots of Populus nigra var. italica and Fraxinus excelsior responded to GA (o.^-i.o mg/g lanolin) and indoleacetic acid (IAA) by producing new tissue. When IAA was applied, lignified vessels wtrt produced. Applications of GA only resulted in formation of tissue consisting of small unlignified cells. Wareing concluded that although treatment with GA stimulated division of cambial initials, the derived cells underwent little vacuolation or lignification, and that typical xylem was not formed. In this investigation the cambium of the stem of treated Coleus bhimei and Sahia splendits plants was stimulated by applications of GA. However, in contrast to the findings of Wareing, this was accompanied by lignification of the derived cells. Alteration in size and shape of leaves on plants treated with GA has been reported in the literature frequently. Gray (1957) reported that treated tomato leaves lost their dentate shape and became entire; leaves of tobacco and African violets became longer and narrower ; pepper leaves exhibited an undulated surface and leaves of pinto beans increased in area. The changes in leaf morphology effected by GA treatment during this investigation were similar to those reported by other investigators. The postulation that a concentration of GA sufficient to elicit maximum elongation of the shoot axis will retard or completely prevent the development of secondary or adventitious roots, is generally agreed. According to Stowe and Yamaki (1957) the inhibition of root growth resulting from GA treatment is not as conclusive as the inhibition of root initiation on cuttings. Kato (1958) reported that GA not only inhibited root formation, it also counteracted the stimulative effect of applied IAA on the initiation of roots. Treatment of Coleus blumei cuttings in various ways indicated that GA and its method of application influenced, but did not inhibit, the rooting response. Microscopic examination revealed that numerous root primordia were initiated within 9 days and ultimately adventitious roots were produced on GA-treated plants. These results are in contrast to the findings of Kato (1958) and others (Alvim, i960; Marth, Audia and Mitchell, 1956). The concentration of GA used might be a factor limiting the development of roots of different species. Concentrations as low as 3-5 ppm may be stimulative (Richardson, 1958; Whaley and Kephart, 1957) while higher concentrations ( ppm) tend to inhibit root growth (Leivonen, 1958; Marth et al, 1956). ACKNOWLEDGMENTS Published with the permission of the Director of the Wisconsin Agricultural Experiment Station. Supported, in part, by the Research Committee of the Graduate School from funds supplied by the Wisconsin Alumni Research Foundation.

Effect of gibberellic acid on Coleus, etc. 543 REFERENCES ALVIM, P. T. (i960). Net assimilation rate and growth behavior of bean as affected by gibberellic acid, urea and sugar sprays. P/. P/(vs;o/.

5 Effect of gibberellic acid on Coleus, etc. 543 REFERENCES ALVIM, P. T. (i960). Net assimilation rate and growth behavior of bean as affected by gibberellic acid, urea and sugar sprays. P/. P/(vs;o/., Loj/cnifer, 35, 285. ARNEY, S. E. & MANCINELLI, P. (1966). The basic action of gibberellic acid in elongation of 'Meteor' pea stems. Neti' PhytoL, 65, 161. BOSTR.ACK, J. M. & STRUCKMEYER, B. E. (1964). Effects of gibberellic acid on the anatomy of soybeans (Glycine max). Am. J. Bot., 51, 611. BR.'IDLEY, M. V. & CRANE, J. C. (1957). Gibberellin-stimulated cambial acti\ity in stems of apricot spur shoots. Science, N.Y., 126, 972. BRIAN, P. W. (1958). Role of gibberellin-like hormones in regulation of plant growth and flowering. Nature, Lond., 181, BRIAN, P. W., ELSON, G. W., HEMMINC, H. G. & RADLEY, M. (1954). The plant-growth-promoting properties of gibberellic acid, a metabolic product of the fungus Gibberella fujikuroi. J. Sei. Fd A«ric. 5, 602. BRIAN, P. W. & GROVE, J. F. (1957). Gibberellic acid. Endeavour, 16, 161. CHERRY, L., LUND, H. A. & EARLEY, E. B. (i960). Effect of gibberellic acid on growth and yield of corn. Agron.J., 52, 167. COOPER, J. P. (1958). The effect of gibberellic acid on a genetic dwarf in Lolium pereiine. New PhytoL, 57, DvRE, L. S. & JENSEN, W. A. (1957). The influence of gibberellic acid and indoleacetic acid on cotton embyros cultured in vitro. Bot. Ga:., 118, 254. GRAY, R. A. (1957). Alteration of leaf size and shape and other changes caused by gibberellins in plants. Am. J. Bot., 44, 674. GREUL.'iCH, V. A. & HAESLOOP, J. G. (1958). The influence of gibberellic acid on cell division and cell elongation in Phaseolus vulgaris. Am. J. Bot., 45, 566. HABER, A. H. & LuiPPOLD, H. J. (i960). Effects of gibberellin on gamma-irradiated wheat. Am.J. Bot., 47, 140. HoAGUND, D. R. & ARNON, D. I. (1938). The water-culture method for growing plants without soil. Circ. Calif, agric. Exp. Stn, 347. KATO, J. (1958). Studies on the physiological effect of gibberellin II. On the interaction of gibberellin with auxins and growth inhibitors. Physiologia PL, 11, 10. KATO, Y. (1955). Responses of plant cells to gibberellin. Bot. Gaz., 117, ib. KoLLER, D., HiGHKiN, H. R. & C.\so, O. H. (i960). Effects of gibberellic acid on stem apices of vernahzable grasses. Am.J. Bot., 47, 518. LEIVONEN, H. (1958). The effects of gibberellins and indoleacetic acid on the root cells of Narcissus tazetta (L.). Physiologia PL, 11, 838. MARTH, P. C., AUDIA, W. V. & MITCHELL, J. W. (1956). Effects of gibberellic acid on growth and development of plants of various genera and species. Bot. Gaz., 118, 106. RlCH.\RDSON, S. D. (1958). Radicle elongation of Pseudotstiga menziesii in relation to light and gibberellic acid. Nature, Lond., 181, 429. SACHS, R. M., BRETZ, C. F. & LANG, A. (1959). Shoot histogenenesis: The early effects of gibberellin upon stem elongation in two rosette plants. Am.J. Bot., 46, 376. SASS, J. E. (1958). Botanical Microtechnique. Iowa State University Press, Ames, Iowa. SoosT, R. K. (1959). Effects of gibberellic acid on genetic characters in two tomato lines. Bot. Gaz., 121, 114- STOWE, B. B. & YAMAKI, T. (19^7). The history and physiological action of the gibberellins. A. Rev. PL PhysioL, 8, 181. WAREING, P. F. (1958). Interaction between indoleacetic acid and gibberellic acid in cambial activity. Nature, Lond., 181, WHALEY, G. W. & KEFHART, J. (1957). Effect of gibberellic acid on growth of maize roots. Science, AM'., 125, 234.

JACK M. BOSTRACK AND B. ESTHER STRUCKMEYER EXPLANATION OF PLATES PLATE 27 Xo. I. Longitudinal section of shoot apex of an untreated Antirrhinum majus plant, x 81. No. 2. Longitudinal section of shoot apex of A.

6 JACK M. BOSTRACK AND B. ESTHER STRUCKMEYER EXPLANATION OF PLATES PLATE 27 Xo. I. Longitudinal section of shoot apex of an untreated Antirrhinum majus plant, x 81. No. 2. Longitudinal section of shoot apex of A. majus plant treated with 50 mg/1 GA showing elongation of sub-apical internodes as a result of cell division, x 81. No. 3. Transverse section of shoot apex of untreated A. majus plant, x 60. No. 4. Transverse section of shoot apex of A. majus plant treated with 50 mg,'. G.A. Fewer leaf primordia in terminal bud. x 60. No. 5. Transverse section of fourth internode of untreated A. majus plant, x 33. No. 6. Transverse section of fourth internode from stem tip of A. majus plant treated with 50 mg/1 G.A. X 33. N'o. 7. Buds of axillary shoot (arrow) oi A. majus plant treated with 50 mg/1 GA (right) hanging in a pendant manner as a result of degenerated tissue. Normal axillary buds in untreated plant at left. PLATE 28 No. 8. Longitudinal section of untreated Salvia splendens plant showing short sub-apical internodes. X 12. No. 9. Longitudinal section of shoot apex of S. splendens plant treated with 50 mg/1 GA showing early elongation of sub-apical internodes and thinner stems, x 12. No. 10. Trans\ erse section of Coleus blumei cutting grown m distilled water for 26 days, x 40. No. II. Trans\'erse section of C. blumei cutting grown in distilled water and sprayed with 50 mg/1 GA for 26 days. Note increased activity of cambial initials resulting in production of xylem parenchyma, x 40. N'o. 12. Cuttings of C. blumei plants 33 days after initiation of treatment. Treatments are from left to right: untreated grown in distilled water; untreated grown in Hoagland's nutrient solution; cuttings grown with stems immersed in 50 mg/1 GA; plants sprayed with 50 mg/1 GA and grown in distilled water; plants sprayed with 50 mg/1 GA and grown in Hoagland's nutrient solution. Least amount of root growth occurred on cuttings grown in G.A solution (centre) and greatest root development on untreated and sprayed cuttings grown in Hoagland's solution.

7 THE NEW PIIY'rOLOGIS'l\66, 4 27 JACK M. BOSTR.ACK AM. B. HS'I'HKR S'VRl'CKMK\EH KFFE('T OF (ilhherelllc 4C1D ON COLEL'S, ETf\ i faciua pai;,- 544)

THE NEW PHYTOf.OGIST, 66, 4 PLATE 28 12 JACK M.

8 THE NEW PHYTOf.OGIST, 66, 4 PLATE JACK M. BOSTRACK ANU B. ESTHER STRUCKMEYER ON COLEUS, ETC. OF GIBBERELLIC ACID

INTERACTION OF GIBBERELLIC ACID AND INDOLE- ACETIC ACID IN THE DIFFERENTIATION OF WOUND VESSEL MEMBERS

INTERACTION OF GIBBERELLIC ACID AND INDOLE- ACETIC ACID IN THE DIFFERENTIATION OF WOUND VESSEL MEMBERS BY L. W. ROBERTS AND D. E. FOSKET Department of Biological Sciences, University of Idaho, Moscow,