Effect of Foliar-Applied Salicylic Acid on Cotton Flowering, Boll Retention, and Yield.J.J. Heitholt [1,2] J.H. Schmidt [2] J.E. Mulrooney [3] Salicylic acid salicylic acid or 2-hydroxybenzoic acid, C6H4(OH)CO2H, a colorless, crystalline organic carboxylic acid that melts at 159°C;; it is soluble in ethanol and ether but is only slightly soluble in water. (2-hydroxybenzoic acid) may help regulate several plant functions, including systemic acquired resistance In plants, systemic acquired resistance (SAR) is a "whole-plant" resistance response that occurs following an earlier localized exposure to a pathogen. SAR is analogous to the innate immune system found in animals, and there is evidence that SAR in plants and innate immunity in to pathogens and the formation of flowers. The objective of this study was to characterize the effects of foliar-applied salicylic acid on cotton (Gossypium hirsutum Gossypium hirsutum, n See gossypol. L.) flowering, boll retention, and yield. Field experiments were conducted at two Mississippi locations in 1995 and at one location in 1997. In 1995, a single application of sodium salicylate Noun 1. sodium salicylate - a crystalline salt used as an analgesic and antipyretic analgesic, anodyne, pain pill, painkiller - a medicine used to relieve pain (0, 17.1, 51.3, or 171 g [ha.sup.-1]) was made two to three weeks prior to flowering. In 1997, nine sequential applications of sodium salicylate (51.3 g [ha.sup.-1]) or salicylic acid (44.3 g [ha.sup.-1]) or a check solution (Tween tween n. A child between middle childhood and adolesence, usually between 8 and 12 years old. [Blend of teen1 and between.] 20, polyoxyethylene sorbitan sorbitan /sor·bi·tan/ (sor´bi-tan) any of the anhydrides of sorbitol, the fatty acids of which are surfactants used as emulsifiers in pharmaceutical preparations; see also polysorbate 80. monolaurate only) were made beginning when the first floral buds were present and ending at first flower. In one of the 1995 tests and in the 1997 test, the cotton was not treated with insecticides after planting. Although physiological responses to exogenously-applied salicylic acid on cotton have been reported elsewhere, in the present study, flower production, boll retention, and yield were not significantly affected. Foliar foliar pertaining to or having the quality of leaves. applications of salicylic acid have been shown to affect flower induction Physiological process in the plant by which the shoot apical meristem becomes competent to develop flowers. Biochemical changes at the apex, particularly those caused by cytokinins, accompany this process. and flower numbers in several species. In minute duckweed duckweed, any plant of the genus Lemna and sometimes of related genera. Duckweeds are tiny floating or submerged aquatic plants with reduced or obsolete roots. They flower only rarely, and their flowers are small and inconspicuous. (Lemna paucicostata), salicylic acid increased the percent of plants flowering under both long- and short-day lengths (Watanabe and Takimoto, 1979). Kharana and Cleland (1992) showed that 10 [micro]M salicylic acid or benzoic acid benzoic acid (bĕnzō`ĭk), C6H5CO2H, crystalline solid organic acid that melts at 122°C; and boils at 249°C;. It is the simplest aromatic carboxylic acid (see aryl group and carboxyl group). induced flowering of L. paucicostata LP6. Both exogenous salicylic acid and the salicylic acid fraction of brown ambrosia ambrosia (ămbrō`zhə), in Greek mythology, food and drink with which the Olympian gods preserved their immortality. Extraordinarily fragrant, ambrosia was probably conceived of as a purified and idealized form of honey. aphid (Dactynotus ambrosiae) honeydew that had been feeding on cocklebur cocklebur or clotbur, any species of the genus Xanthium, widely distributed, coarse annual plants of the family Asteraceae (aster family). , Xanthium strumarium L. induced flowering in inflated duckweed, L. gibba (Cleland and Ajami, 1974). However, in Japanese morningglory {[Ipomoea Ipomoea widespread genus of poisonous vines of the family Convolvulaceae; may contain various toxins including the indole alkaloid lysergic acid, furanoterpenes, indolizidine alkaloids (swainsonine). Includes I. asarifolia (salsa), I. nil (L.) Roth]=[Pharbitis nil (L.) Choisy]}, salicylic acid reduced flowering (Groenewald and Visser, 1978). In mung bean mung bean n. 1. An Asian plant (Vigna radiata) in the pea family, widely cultivated for its edible seeds and pods. It is the chief source of bean sprouts. 2. The seeds or pods of this plant. (Vigna radiata L.), three foliar sprays of 7.2 and 72 [micro]M salicylic acid increased seed yield per plant by 19 and 46%, respectively (Singh and Kaur, 1980). In cheena millet (Panicum miliaceum L.), salicylic acid increased plant height and grain number (Datta and Nanda, 1985). In addition to possible involvement in flowering, the knowledge of the role of salicylic acid in systemic acquired resistance and pest resistance has recently been advanced (Raskin, 1992; Delaney et al., 1994; Ryals et al., 1996; Sticher et al., 1997). Plant drenches of salicylic acid at 61 and 123 [micro]M also increased cotton root gossypol gossypol /gos·sy·pol/ (gos´i-pol) a toxin found in cottonseed and detoxified by heating; it has male antifertility properties, apparently having its effects in the seminiferous tubules. gos·sy·pol n. concentration by 35 and 47%, respectively (Khoshkhoo et al., 1993). Soaking cotton seedling root systems for 30 s in 0.1% salicylic acid reduced shoot fresh weight and root-knot nematode (Meloidogyne incognita race 3) egg numbers per root biomass (Hedin et al., 1995). Herbivory by Helicoverpa zea (Boddie) increased cotton leaf salicylic acid and [H.sub.2][O.sub.2] concentration (Bi et al., 1997), a response frequently observed following pathogenesis (Klessig and Malamy, 1994). However, foliar applications of salicylic acid did not affect cotton foliar resistance to H. zea. Hypersensitivity hypersensitivity, heightened response in a body tissue to an antigen or foreign substance. The body normally responds to an antigen by producing specific antibodies against it. The antibodies impart immunity for any later exposure to that antigen. response to bacterial blight (Xanthomonas campestris pv malvacearum) in cotton was reported to be related to the accumulation of salicylic acid in cotyledons (Martinez et al., 2000). Since the agronomic a·gron·o·my n. Application of the various soil and plant sciences to soil management and crop production; scientific agriculture. ag effects of salicylic acid on cotton in the mid-south USA have not been reported, the objective of this study was to determine whether foliar applications of sodium salicylate or salicylic acid would increase yield, flowering, and boll retention in field-grown cotton. MATERIALS AND METHODS Cotton (cv. Deltapine 50) was grown in the field in two locations (3 km apart) near Stoneville, MS in 1995. Seed were planted on 18 April 1995 (Test 1) at one location on a mixed soil type (a Bosket very fine sandy loam loam, soil composed of sand, silt, clay, and organic matter in evenly mixed particles of various sizes. More fertile than sandy soils, loam is not stiff and tenacious like clay soils. Its porosity allows high moisture retention and air circulation. and a Dundee very fine sandy loam) and on 10 May 1995 for the second location on Dundee silty clay (Test 2). No attempt was made to match planting dates between Test 1 and Test 2. In 1997, Test 3 was planted on 23 May at the same site where Test 1 was two years earlier. Conventional fungicide fungicide (fŭn`jəsīd', fŭng`gə–), any substance used to destroy fungi. Some fungi are extremely damaging to crops (see diseases of plants), and others cause diseases in humans and other animals (see fungal infection). seed-treatment and planting procedures were used. Row spacing was 102-cm and plots were four rows wide and 5.2 m long. Final plant stand density averaged 11 plants [m.sup.-2]. In Tests 1 and 2, foliar treatments were applied on only one date during the floral bud stage, approximately two to three weeks before first bloom. The treatments consisted of one application of 0, 0.625, 1.87, or 6.25 mM Na salicylate salicylate (səlĭs`əlāt'), any of a group of analgesics, or painkilling drugs, that are derivatives of salicylic acid. The best known is acetylsalicylic acid, or aspirin. (Sigma Chemical Co., St. Louis, MO). All solutions contained 0.05% (v/v) Tween 20 (polyoxyethylene sorbitan monolaurate, Sigma Chemical Co., St. Louis, MO) and were applied using a backpack sprayer with flat-fan nozzles. The rate of solution applied was 171 L [ha.sup.-l] (17.1 mL [m.sup.-2]). Thus, rates of sodium salicylate were 0, 17.1, 51.3, and 171 g [ha.sup.-l]. Application dates were 14 June 1995 for Test 1 and 15 June 1995 for Test 2. Initial flowering for Test 2 occurred approximately one week later than flowering for Test 1. An additional unsprayed check treatment, was included in both tests. Because the results in Tests 1 and 2 indicated that a one-time salicylic acid spray had little effect, we changed to multiple treatments in Test 3 to consist of a check (Tween 20 only), foliar sprays of 1.87 mM sodium salicylate (pH 5.4) with 0.05% Tween 20, and foliar sprays of 1.87 mM salicylic acid (pH 3.1) also with 0.05% Tween 20. Application dates were 16 June, 18 June, 20 June, 23 June, 25 June, 27 June, 1 July, 8 July, and 15 July 1997. The spray rate for each application was 17.1 mL [m.sup.-2] (171 L [ha.sup.-l]). For sodium salicylate and salicylic acid, respectively, seasonal totals of 462 g and 395 g were applied per ha. In Tests 1 and 3, plots were not treated with insecticide. In Test 2, plots were treated with insecticide on 27 May, 10 June, 22 June, 1 July, 15 July, 3 Aug., and 12 Aug. when insect pests typical of mid-South USA cotton reached threshold levels. On selected dates during flowering (approximately twice weekly), white flowers were counted on one of the inner rows of each plot (5.28 [m.sup.2] per plot). In upland cotton, petals of blooms are white or cream colored on the day of anthesis. Petals are inconspicuous in·con·spic·u·ous adj. Not readily noticeable. in  con·spic the day
prior to anthesis and are pink or red the day following anthesis. Thus,
it is possible to find and count all flowers at anthesis on a given day
without concern for counting flowers that reached anthesis on an earlier
or later date. An estimate of flowers reaching anthesis, on days when
counts were not made, was made by interpolation interpolationIn mathematics, estimation of a value between two known data points. A simple example is calculating the mean (see mean, median, and mode) of two population counts made 10 years apart to estimate the population in the fifth year. . Subsequently, total seasonal flower production was calculated (Heitholt, 1993). As the crop matured, open bolls were counted and hand-harvested from 4.6 m2 of one inner row per plot (same row as that used for the flower count). Hand harvest dates were 25 Aug., 6 Sept., 18 Sept., 27 Sept., and 6 Oct. 1995 for Test 1. Harvest dates were 7 Sept., 27 Sept., and 9 Oct. 1995 for Test 2. For Test 3, harvest dates were 9 Sept., 16 Sept., 30 Sept., 6 Oct., 16 Oct., 23 Oct., and 3 Nov. 1997. Boll retention (seasonal boll number divided by seasonal flower number), yield, boll numbers, and boll size (lint lint - A Unix C language processor which carries out more thorough checks on the code than is usual with C compilers. Lint is named after the bits of fluff it supposedly picks from programs. per boll) were determined. The treatments in all three experiments were arranged in a randomized ran·dom·ize tr.v. ran·dom·ized, ran·dom·iz·ing, ran·dom·iz·es To make random in arrangement, especially in order to control the variables in an experiment. complete block design with six replications. An analysis of variance (ANOVA anova see analysis of variance. ANOVA Analysis of variance, see there ) was performed on all data. For Tests 1 and 2, sources of variation were replicate, control, rate (control), and error. For Test 3, only three treatments were used, so the sources of variation were replicate, treatment, and error. RESULTS AND DISCUSSION Tests 1 and 2 indicated that none of the treatments significantly affected yield (Table 1). It is possible that treatment of plants with salicylic acid can induce defenses against microbes, insects, and herbivores (Metraux and Raskin, 1992). Therefore, we originally hypothesized that a positive effect from salicylate was more likely in Test 1, which did not receive insecticide, than in Test 2. Other yield-related factors, such as flower production, boll numbers, boll retention percentage, and boll size were likewise unaffected by foliar-applied salicylate (Table 1). Flower production, boll numbers, and boll retention in this study were typical of previous studies with Deltapine 50 (Heitholt, 1993). In Test 3, a severe insect infestation infestation /in·fes·ta·tion/ (-fes-ta´shun) parasitic attack or subsistence on the skin and/or its appendages, as by insects, mites, or ticks; sometimes used to denote parasitic invasion of the organs and tissues, as by helminths. greatly reduced flowering and yield. Yield was not significantly (P=0.08) affected by either salicylic acid or sodium salicylate (Table 2). Flower numbers, boll retention, and boll size were also unaffected. Others have reported that [10.sup.-4] to [10.sup.-10] M salicylic acid decreased abscisic acid-induced leaf abscission (as measured by petiole petiole /pet·i·ole/ (pet´e-ol) a stalk or pedicle. epiglottic petiole the pointed lower end of the epiglottic cartilage, attached to the thyroid cartilage. breakage) in kidney bean kidney bean phaseolusvulgaris. (Phaseolus vulgaris L.) (Apte and Laloraya, 1982). In Tests 1, 2, and 3, differences in leaf damage due to treatments were not observed. However, a high incidence of boll rot was generally observed in Test 3 regardless of treatment (no data collected). In contrast to Patil and Wele (1992) factors other than salicylic acid obviously controlled the reproductive growth in field studies reported here. In the study by Patil and Wele (1992), salicylic acid may have increased yield by decreasing transpiration transpiration, in botany, the loss of water by evaporation in terrestrial plants. Some evaporation occurs directly through the exposed walls of surface cells, but the greatest amount takes place through the stomates, or intercellular spaces (see leaf). in a water-limited environment. The finding that Test 1 (no insecticides) exhibited a greater yield than Test 2 (insecticides applied) needs an explanation. In Tests 1 and 2 (1995), extremely warm August temperatures in the mid Delta impeded reproductive growth. Reproductive development of the earlier planted cotton (i.e., Test 1) was about one week further advanced than Test 2. Although one week is not extremely long, fruit growth in Test 1 apparently escaped much the warm temperatures that occurred in August 1995. This hypothesis is supported by the observation that earlier maturing cultivars tended to outyield later maturing cultivars at sites adjacent to Tests 1 and 2 that year (Heitholt and Meredith, 1998). In Test 3 (1997), the low yields (395 to 487 kg [ha.sup.-1] vs. 708 to 1040 kg [ha.sup.-l] in 1995) were likely due to a late planting date combined with high insect pressure. Despite salicylic acid's lack of effect here, the results should not be interpreted to preclude the importance of salicylic acid in systemic acquired resistance or its role for protecting cotton against insects and pathogens. Future studies need to characterize genotypic differences in response to salicylic acid concentrations and determine whether those differences can affect pathogen resistance or yield. ACKNOWLEDGMENT The authors thank D. Boykin for statistical advice. (1.) Author for correspondence. Current address: Texas Agricultural Research and Extension Center, 17360 Coit Road, Dallas, TX 75252, j-heitholt@tamu.edu (2.) USDA-ARS USDA-ARS United States Department of Agriculture-Agricultural Research Service , P.O. Box 345, Stoneville, MS 38776 and (3.) USDA-Forest Service, Starkville, MS 39759 LITERATURE CITED Apte, P.V., and M.M. Laloraya. 1982. Inhibitory action of phenolic phe·no·lic adj. Of, relating to, containing, or derived from phenol. n. Any of various synthetic thermosetting resins, obtained by the reaction of phenols with simple aldehydes and used as adhesives. compounds on abscisic acid-induced abscission. J. Exp. Bot. 33:826--830. Bi, J.L., J.B. Murphy, and G.W. Felton. 1997. Does salicylic acid act as a signal in cotton for induced resistance to Heliocoverpa zea? J. Chem. Ecol. 23:1805-1818. Cleland, C.F., and A. Ajami. 1974. Identification of the flower inducing factor isolated from aphid honeydew as being salicylic acid. Plant Physiol. 54:904-906. Datta, K.S., and K.K. Nanda. 1985. Effect of some phenolic compounds and gibberellic acid on growth and development of cheena millet (Panicum miliaceum L.). Indian J. Plant Physiol. 28:298--302. Delaney, T.P., S. Uknes, B. Vernooij, L. Friedrich, K. Weymann, D. Negrotto, T. Gaffney, M. Gut-Rella, H. Kessmann, E. Ward, and J. Ryals. 1994. A central role of salicylic acid in plant disease resistance. Science 266:1247-1250. Groenewald, E.G E.G For Example ., and J.H. Visser. 1978. The effect of arachidonic acid arachidonic acid /arach·i·don·ic acid/ (ah-rak?i-don´ik) a polyunsaturated 20-carbon essential fatty acid occurring in animal fats and formed by biosynthesis from linoleic acid; it is a precursor to leukotrienes, prostaglandins, and , prostaglandin prostaglandin (prŏs'təglăn`dən), any of a group of about a dozen compounds synthesized from fatty acids in mammals as well as in lower animals. and inhibitors of prostaglandin synthetase synthetase /syn·the·tase/ (-the-tas) a term used in the names of some of the ligases, no longer favored because of its similarity to synthase and its emphasis on reaction products. syn·the·tase n. , on the flowering of excised Pharbitis nil shoot apices a·pi·ces n. A plural of apex. under different photoperiods. Z. Pflanzenphysiol. 88:423-429. Hedin, P.A., B. Tang, and R.G. Creech. 1995. Effect of bioregulators on development and reproduction of root-knot nematode in cotton plant roots. Miss. Agric. Forest. Exp. Stn. Bulletin 1028, 6 p. Heitholt, J.J. 1993. Cotton boll retention and its relationship to lint yield. Crop Sci. 33:486-490. Heitholt, J.J., and W.R. Meredith, Jr. 1998. Yield, flowering, and leaf area index The Leaf Area Index or LAI is the ratio of total upper leaf surface of a crop divided by the surface area of the land on which the crop grows. The LAI is a dimensionless number. of okra-leaf and normal-leaf cotton isolines. Crop Sci. 38:643-648. Kharana, J.P., and C.F. Cleland. 1992. Role of salicylic acid and benzoic acid in flowering of a photoperiod-insensitive strain of Lemna paucicostata LP6. Plant Physiol. 100:1541-1546. Khoshkoo, N., P.A. Hedin, and J.C. McCarty, Jr. 1993. Effects of bioregulators on the terpenoid ter·pene n. Any of various unsaturated hydrocarbons, C10H16, found in essential oils and oleoresins of plants such as conifers and used in organic syntheses. aldehydes in root-knot nematode infected cotton plants. J. Agric. Food Chem. 41:2442--2446. Klessig, D.F., and J. Malamy. 1994. The salicylic acid signal in plants. Plant Mol. Biol. 26:1439--1458. Martinez, C., J.C. Baccou, E. Bresson, Y. Baissac, J.F. Daniel, A. Jalloul, J.L. Montillet, J.P. Geiger, K. Assigbetse, and M. Nicole. 2000. Salicylic acid mediated by the oxidative burst is a key molecule in local and systemic responses of cotton challenged by an avirulent a·vir·u·lent adj. Not virulent. race of Xanthomonas campestris pv malvacearum. Plant Physiol. 122:757--766. Metraux, J.P., and I. Raskin. 1993. Role of phenolics in plant disease resistance. Pages 191--209 in I. Chet ed. Biotechnology in plant disease control. Wiley-Liss, Inc. Patil, S.M., and A.D. Wele. 1992. Yield of cotton as influenced by antitranspirants and land surface modification. Punjabrao Krishi Vidyapecth Res. J. 16:265-266. Raskin, I. 1992. Role of salicylic acid in plants. Annu. Rev Plant Physiol. Plant Mol. Biol. 43:439-463. Ryals, J.A., U.H. Neuenschwander, M.G. Willits, A. Molina, H.-Y. Steiner, and M.D. Hunt. 1996. Systemic acquired resistance. Plant Cell 8:1809-1819. Singh, G., and M. Kaur. 1980. Effect of growth regulators on podding and yield of mung bean (Vigna radiata L. Wilczek). Indian J. Plant Physiol. 23:366-370. Sticher, L, B. Mauch-Mani, and J.P. Metraux. 1997. Systemic acquired resistance. Annu. Rev. Phytopathol. 35:235-270. Wantanabe, K., and A. Takimoto. 1979. Flower-inducing effects of benzoic acid and some related compounds in Lemna paucicostata 151. Plant Cell Physiol. 20:847-850.
Effect of sodium salicylate on flower production, boll characteristics,
and lint yield of Deltapine 50 cotton in 1995 at two locations.
Na Salicylate Seasonal
Treatment Flowers Bolls Boll
Test 1 number [m.sup.-2] Retention Lint Yield
No Insecticide % kg [ha.sup.-1]
Unsprayed 104 65.7 63 970
Tween 20 only 107 63.9 60 973
17.1 g [ha.sup.-1] 110 66.2 60 1010
51.3 g [ha.sup.-1] 110 63.3 57 938
171.0 g [ha.sup.-1] 106 70.2 66 1040
LSD (0.05) [a] ns ns ns ns
Test 2
Conventional
Insecticide
Unsprayed 114 55.7 49 764
Tween 20 only 117 54.6 47 739
17.1 g [ha.sup.-1] 114 53.2 47 725
51.3 g [ha.sup.-1] 110 54.0 50 751
171.0 g [ha.sup.-1] 114 49.5 43 708
LSD (0.05) [a] ns ns ns ns
Na Salicylate
Treatment
Test 1 Boll Size
No Insecticide g (lint)
Unsprayed 1.47
Tween 20 only 1.53
17.1 g [ha.sup.-1] 1.52
51.3 g [ha.sup.-1] 1.48
171.0 g [ha.sup.-1] 1.48
LSD (0.05) [a] ns
Test 2
Conventional
Insecticide
Unsprayed 1.37
Tween 20 only 1.37
17.1 g [ha.sup.-1] 1.36
51.3 g [ha.sup.-1] 1.40
171.0 g [ha.sup.-1] 1.44
LSD (0.05) [a] ns
(a.)LSD values for Test 1 were 11, 5.3, 9, 81, and 0.07 and for Test 2
were 13, 6.3, 14, 70, and 0.12.
Effect of nine sequential pre-bloom foliar sprays of Tween 20, 1.87 mM
salicylic acid, or 1.87 mM sodium salicylate on flower production, boll
characteristics, and lint yield of Deltapine 50 cotton in Test 3 (1997).
The field was not treated with insecticide.
Salicyclic Acid Seasonal Bolls Boll Lint
Treatment Flowers Retention Yield
number [m.sup.-2] % kg [ha.sup.-1]
Tween 20 only 37.2 31.4 85.7 432
Salicyclic acid 40.1 33.1 83.2 487
Na salicylate 34.9 27.3 80.3 395
LSD (0.05) [a] ns ns ns ns
Salicyclic Acid Boll
Treatment Size
g (lint)
Tween 20 only 1.39
Salicyclic acid 1.48
Na salicylate 1.46
LSD (0.05) [a] ns
(a.)LSD values for Test 3 were 7.9, 5.3, 14.2, 75, and 0.09.
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