Rooting Response of Feijoa Sellowiana and Myrica Rubra
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TAYLOR AND JOINER: FEIJOA - MYRICA 363 sawdust plunging medium the only treatment treatments (1£ pounds of sodium nitrate and comparisons attaining significance was that of 10 ounces of sodium nitrate and 5 ounces of L2 and L3. muriate of potash per 100 square feet, re Discussion spectively), was initiated August 6, 1959. The data indicate that excessive shading Under the conditions of this experiment, as used by some growers might materially re light and plunging media were the factors duce bud set. It is also indicated that the ad that affected bud formation in gardenia. Fer ditional nitrogen required by bacteria breaking tilizer treatments had no effect. down the sawdust may have been obtained at Bud production was low under 50 percent the expense of the plants. This was reflected saran shade and there was no difference be in reduced bud production. tween the peat and sawdust plunging media, Summary but it increased significantly in both plung A factorial experiment with Gardenia jas- ing media when the plants were given full minoides 'Veitchii/ combining three light con sun from October 1 until experiment was ter ditions (full sun, 50 percent saran shade and minated. Peat was superior to sawdust as a 50 percent saran shade from August 6 to Octo plunging medium only when the plants were ber 1, 1959, then full sun until experiment's grown in full sun. Plants given full sun and termination, May 4, 1960), two plunging with the pots plunged in peat produced the media (peat and sawdust) and two fertilizer most buds. ROOTING RESPONSE OF FEIJOA SELLOWIANA AND MYRICA RUBRA AS AFFECTED BY 2,3,5-TRIIODOBENZOIC ACID AND 3-INDOLEBUTYRIC ACID John B. Taylor and J. N. Joiner (2) high concentrations of TIBA antagonize the effects of externally applied auxins and University of Florida native auxins, and (3) toxic influences of Gainesville high concentrations @f TIBA are non-specific and eventually lead to the death of cells. Propagators of ornamental plant material These same reactions are also applicable have always been faced with the problem of to root growth. At concentrations of 10-8 to 10-° difficult-to-root species. The use of mist pro M synergistic action of TIBA with native or pagation and growth regulators has in many externally applied auxin is apparent. At high instances overcome this difficulty. However, er molarities, 10-8 to 10-5 antagonism occurs, there still remain many plants difficult to root and finally toxicity is manifest in the range even under the best commercial practices. of 10-3 to 10-4M. Feijoa sellowiana and Myrica rubra are clas Aberg (1) offers a probable explanation of sified in this category and were chosen as in the synergistic action of TIBA as an effect on dex plants for these experiments. the enzymatic systems regulating the metabo Zimmerman and Hitchcock (14) were the lism of 3-indoleacetic acid (IAA) in plant cells. first to test 2,3,5-triiodobenzoic (TIBA) as TIBA in low concentrations would increase the a plant growth regulating substance. They IAA synthesis and produce a greater hormonal classified it as a growth regulator which is response up to a threshold level. active in inducing modification of plant or Veldstra and Booij (11) propose that TIBA gans, but inactive in causing cell elongation competes with auxin for inactive sites in the or root formation. cell plasm thereby affording a greater op Aberg (1) in 1953, summarized the effects portunity for free auxin molecules to attach of TIBA on shoot parts as follows: (1) in very to active sites within the plant. low concentrations TIBA has a weak auxin ef Audus and Das (3) assume that the ef fect which is thought to be the result of sy- fect of TIBA or any growth regulating sub nergism between it and endogenous auxin; stance is a function of die amount of that ma- 364 FLORIDA STATE HORTICULTURAL SOCIETY, 1960 terial absorbed at an active center and the are those previously used by Taylor and Join amount absorbed is proportional to the rela er (10). They are: (1) no roots; (2) slight tive activity of the substance. These workers rooting; (3) moderately rooted; (4) heavily also visualize two active growth centers—one rooted; (5) very heavily rooted. This is il which promotes and the other which inhibits lustrated for feijoa in Figure 1. growth. The authors asserted that growth re sponse to auxin application could result from: (1) exogenous auxins applied in sufficient concentrations displaces endogenous auxin in supraoptimal amounts thereby reducing in hibition and stimulating growth; (2) endo genous auxin may not be present or in insuf ficient concentrations and the exogenous auxin applied would affect the growth center di rectly, or (3) if optimal amounts of auxin and antiauxin are applied the inhibition of growth is due to the inhibition center being acti vated which inhibits the promotion center Fig. 1. "Rooting quality rating" system used for rating due to the greater activity of the antiauxin. FEIJOA SELLOWIANA. Most research workers have placed TIBA in Results the vague, broad classification of antiauxins. The rooting of Myrica rubra cuttings was In general, these substances are thought to not significantly affected by treatment. Only antagonize auxins except when used in very nine of 520 cuttings rooted. minute concentrations. Snyergism occurs if TIBA at the rate of 1.1 ppm (treatment 3) used in combination with an auxin at low con produced a greater percent of rooted cuttings centrations or weak auxin activity if used alone. and a better "rooting quality" score than any Growth promotion by antiauxins is thought of the other treatments (Table 1). Treatment to be the influence of the mediated auxin 3 was the only treatment significantly better system and not the antiauxin alone. than the control (treatment 13), and treat Methods and Materials ment 5 was the only one that significantly de Two experiments were initiated February 27, pressed rooting below that of the control. The 1960, in a greenhouse at Gainesville, to test remaining TIBA treatments were neither sig the effect of TIBA and indolebutyric acid nificantly better nor worse than the control. (IBA) on the rooting of Feijoa sellowiana and None of the IBA treatments (treatments 7, Myrica rubra cuttings. Concentrations of the 8, 9, 10, 11, 12) were significantly better or variables were 0.3 ppm, 0.7 ppm, 1.1 ppm, worse than the control (treatment 13). 3.0 ppm, 7.0 ppm and 11.0 ppm. The control Discussion treatments were distilled water. The treat Joiner (6) produced 90% rooting with feijoa ments of both experiments were assigned in when the cuttings were placed under constant randomized block design. There were four replications and the experimental unit was 10 Table 1. Effect of 2,3,5-triiodobenzoic acid and 3-Indolebutyric acid on rooting of feijoa. cuttings. Treatment Materials Percent Rooting Terminal cuttings, 3 to 5 inches long, were Number Used-FPM Rooted Quality obtained from plants on the University of 1 0.3 TIBA 12.5 1.30 0.7 TIBA 15.0 1.23 Florida campus. Treatments were applied as a 1.1 TIBA 42.3 2.15 24-hour soak after which cuttings were in I 3.0 TIBA 15.0 1.30 5 7.0 TIBA 2.5 1.03 serted in a sterilized medium of 50% peat-50% 6 12.0 TIBA 15.0 1.30 0.3 IBA 22.5 1.50 No. 30 perlite. Intermittent mist was applied I O.7 IBA 20.0 1.23 from 8:00 A. M. until 5:30 P. M. in an un 9 1.1 IBA 16.5 1.35 10 3.0 IBA 15.0 1.28 shaded glass greenhouse. 11 7.0 IBA 7.5 1.05 12 11.0 IBA 10.0 1.25 Duration of the experiment was eight weeks, 13 Control-distilled 15.0 1.30 terminating April 23, 1960. Cuttings were re water L.S.D. .05 .01 moved and percent rooting and "root quality" Between percent rooted means 9.86 13.21 were determined. The "rooting quality" values Between rooting Quality TTK*ftDg 0.28 0.37 TAYLOR AND JOINER: FEIJOA - MYRICA 365 mist during February and March after re ering the endogenous auxin below the thres ceiving a 24-hour soak of 3ppm IBA. Dickey hold level. Again maximum inhibition should (5) working with this plant without hormone occur at treatment six rather than five. found that feijoa rooting was unaffected by Rooting quality as affected by TIBA may season of year. Recent work by Taylor and also be partially explained by the above post- Joiner (1) has shown feijoa to root very poorly ulations but would be subject to the same during July and August under the best treat limitations. ment previously described by Joiner (6). It is possible that maximum stimulation of This experiment has shown that TIBA at rooting by TIBA occurs in the range of l.lppm 1.1 ppm is much more effective in promoting to 3.0 ppm. Previous workers have shown rooting of feijoa than IBA at this or any other that antiauxins have a very narrow range in concentration of TIBA and IBA used. Poole (8) which they act as growth promoters and aux conducting an experiment simultaneously with in synergists. feijoa, using several levels of IBA as spray and Logical explanations of these seeming dis soak treatments, got only 12.5% rooting with crepancies are impossible from the data of this his best treatment. experiment and information available concern These data indicate a narrow or limited ing the action of these auxin and antiauxin ma range in which root promotion occurs as a re terials.