PHYSIOLOGICAL ROLE OF 8-HYDROXYQUINOLINE CITRATE AND SUCROSE IN EXTENDING VASE-LIFE AND

Transcription

1 MAROUSKY: CUT GLADIOLUS STUDIES 409 PHYSIOLOGICAL ROLE OF 8-HYDROXYQUINOLINE CITRATE AND SUCROSE IN EXTENDING VASE-LIFE AND IMPROVING QUALITY OF CUT GLADIOLUS F. J. MAROUSKY Market Quality Research Division Agricultural Research Service U. S. Department of Agriculture Gulf Coast Experiment Station Bradenton Absrtact Cut gladiolus flowers were held in a) water, b) 8-hydroxyquinoline citrate (8-HQC), 3) su crose, and d) 8-HQS and sucrose combined. Data were collected from physiological measure ments in several categories; namely, water up take, relative degree of stomatal opening, and resistance to water flow through stems (vascular blockage). Sucrose decreased stomatal opening and reduced water uptake. Eight-tydroxyquinoline citrate closed stomata, reduced vascular blockage, and increased water uptake. The roles of 8-HQC and sucrose in extending vase-life are considered to be: reducing vascular blockage, in creasing water uptake, and decreasing water loss through transpiration. Introduction Snapdragons (7), carnations (8), stocks (9) and roses (10) have recently been shown to have extended vase life and increased flower quality when held in solutions of quinoline salts and sucrose. Larsen and Cromarty (6) and Larsen and Scholes (7) suggested that the extended life of cut flowers was due to the bactericidal prop erties of quinoline salts. They suggested that cut flowers absorbed more water because of re duced bacterial stem blockage. It is recognized that the presence of bacteria in the keeping solution limits cut flower life (1, 2). Quinoline salts are recognized as bactericides (15) and also control stomatal opening (13, 14). Maintenance of adequate moisture content in cut flowers is important. Cut flowers which in crease or maintain their fresh weight have greater longevity than those which decrease in fresh weight (11, 12). For this reason, fresh weights have been used as a criterion of vase life (1, 2, 10, 11, 12). Aarts (1, 2) showed that cut stocks (Mathiola incana) held in sucrose solution absorbed less water than cut stocks held in water. Aarts postulated that the reduced wa ter uptake was due to the high osmotic poten tial of the sucrose solution. In addition, Aarts showed that sucrose closed Mathiola stomata and reduced transpiration. This phenomenon has also been shown in cut roses treated with sucrose (10). The purpose of this paper is to report the effects of 8-HQC and sucrose on stem blockage, water absorption, and stomatal opening of cut gladiolus. Methods and Materials 'White Friendship' gladiolus were cut in the tight-bud stage and held overnight in water at 45 F. Spikes were graded the following morn ing for uniformity in length and weight and randomly distributed among pint glass jars con taining 200 ml of one of 4 solutions: a) water (control), b) 600 ppm 8-hydroxyquinoline citrate (8-HQC), c) 4% sucrose, and d) 600 ppm 8- HQC and 4% sucrose. Distilled water was used for all solutions. There were twelve replications with a single spike per jar constituting a replica tion. Water absorption Liquid in jars were re newed daily with freshly prepared solutions or water, at which time volume loss was determined. Vascular blockage was determined by a meth od similar to that of Durkin and Kuc (4). Two inch portions were removed from the base of the stems on the 4th day. Vascular blockage was measured in terms of the amount of water pulled through this stem piece at 20 in Hg for 5 min. Stems averaged 10 mm in diameter. Width of stomatal aperture was estimated by the method of Halevy (5). Cardboard with a punched hole of 10 mm diameter was placed over an intact leaf. Mineral oil (10%) in re fined kerosene was placed on the exposed leaf tissue and the time was recorded when 25% of the exposed tissue was infiltrated. Accord ing to Halevy, infiltration time is directly re lated to stomatal opening.

2 410 FLORIDA STATE HORTICULTURAL SOCIETY, 1968 Flower and spike quality Flower quality was evaluated by determining the number of days to senescence of basil floret, number of florets open per spike at time of senescence of basal floret (floret display), and total number of florets opened per spike before wilting or stem collapse. Number of days includes the time elapsed for opening of the basal floret. Fresh weight and spike length were deterimned ini tially and at daily intervals. Data were re corded as per cent change in weight and length. Flowers were held in an air-conditioned laboratory maintained at 74 F ± 2 and 65-75% R. H. Light was supplied continuously by fluorescent fixtures at 200 ft-c. All data were treated by analyses of variance and statistical differences determined between means by Duncan's Multiple Range Test. 60 -f I w 30 - I Q 5 20 f 1 = Control 2 = 600 ppm 8-HQC 3 = 4% Sucrose 4 = 600 ppm 8-HQC -h 4% Sucrose ) I 2 DAYS Fig. I. Daily water uptake by cut 'White Friendship1 held in 8-hydroxyquinoline citrate, sucrose, and a of 8-hydroxyquinoline citrate and sucrose. gladiolus mixture

3 MAROUSKY: CUT GLADIOLUS STUDIES 411 Results Water absorption The amount of water ab sorbed by gladiolus decreased as the flowers senesced (Figure 1). Spikes held in sucrose solution absorbed the least amount of water followed by control, 8-HQC-sucrose, and 8-HQC respectively. During the fourth day, gladiolus spikes held in sucrose, 8-HQC, water, and 8- HQC-sucrose absorbed 24, 49, 23 and 62%, re spectively, of the amount of solution they ab sorbed the first day. Vascular blockage After 4 days of vase-life, stems held in water or sucrose solutions ex hibited the greatest resistance to water flow. The least amount of blockage occurred with 8- HQC treated gladiolus, followed by those held in 8-HQC-sucrose (Table 1). Stomatal opening Stomata of gladiolus held in sucrose or 8-HQC were more closed than stomata of gladiolus held in water. The 8-HQCsucrose treatment had an additive effect and caused greater stomatal closure than either chemical used singly (Table 1). Floret and spike quality Basal florets of gladiolus held in water lasted 4.3 days with 5.3 florets opened per spike at the time of senescence Table 1. Degree of stomatal opening and vascular blockage of 'White Friendship1 gladiolus held in solutions of 8-hydroxyquinoline citrate and sucrose for 4 days. Treatment Stomatal1 openine Vascular^ blockage of basal floret (Table 2). Basal florets of gladi olus spikes held in sucrose or 8-HQC lasted about 1 day longer and had 1 more open floret per spike than controls. Basal florets of spikes held in 8-HQC-sucrose lasted 6.3 days with 8.2 florets opened per spike at time of senescence of basal floret. Gladiolus stems held in water or 8-HQC wilted, and collapsed, about 1 day after senes cence of the basal floret (Table 2). At that time, about 1 additional floret had opened per spike. Gladiolus stems held in sucrose or 8- HQC-sucrose did not wilt or break. Florets con tinued to open on each spike and were similar to opening on an intact flower spike. The stems held in 8-HQC-sucrose did not collapse or wilt after all florets had senesced. Gladiolus held in water reached their maxi mum fresh weight in one day and gradually decreased in fresh weight (Figure 2). By the 6th day, spikes held in water weighed less than they did originally and their vase life was de pleted. Gladiolus held in sucrose reached a maxi mum in fresh weight by the second day, then gradually decreased in weight. Gladiolus held in 8-HQC or 8-HQC-sucrose reached a maximum in fresh weight on the fourth day, then gradu ally decreased in weight. However, by the sixth day the weight of these flowers exceeded the maximum fresh weight attaind by gladiolus held in water or sucrose. Gladiolus held in a solution of 8-HQC-sucrose continued to elongate for 5 days; whereas gladi olus held in water, sucrose, or 8-HQC reached their maximum length in 3 days (Figure 3). Control 3.0a 3 0.2a Discussion 600 ppm 8-HQC 4% sucrose 600 ppm 8-HQC + 4% sucrose 6.6b 8.7C 10.9d ^Stomatal opening measured relatively, values represent seconds required to l.lc 0.3a 0.5b infiltrate 25% of exposed tissue, lower values indicate stomata are more open. 2ml H2O absorbed/stem/5 min. at 20 in Hg. ^Means in a column followed by the same letter(s) are not significantly different at the 1% level. Although the data do not show conclusively that senescence in cut gladiolus is due to water deficiency, they do show that longevity and qual ity are improved by increasing water absorp tion and decreasing blockage. Water absorbed by cut gladiolus was inversely related to the de gree of vascular blockage in the stem. Sucrose did not influence vascular blockage but de creased water absorption. The 8-HQC-sucrose mixture reduced vascular blockage but not to the extent of 8-HQC used singly. Presumably, the osmotic effect (1) of the sucrose reduced the absorption of the 8-HQC; thus, water absorp tion was not as great as 8-HQC used singly. The importance of stomatal opening on gladi olus longevity cannot be overlooked. Both su-

4 412 FLORIDA STATE HORTICULTURAL SOCIETY, 1968 Table 2. Quality measurements for cut 'White Friendship1 gladiolus held in solutions of 8-hydroxyquinoline citrate and sucrose. No. days to No. florets senescence open at of basal senescence of Days to stem Treatment floret basal floret collapse Control 4.3* l 5.3a ppra 8-HQC 5.2b 6.3b o sucrose 5.3b 6.8b ppra 8-HQC 4% sucrose 6.3C 8.2C in a column followed by the same letter(s) are not significantly different at the 1% level. 2Spikes held in sucrose or 8-HQC-sucrose did not wilt or collapse. crose and 8-HQC closed stomata. Gladiolus held in sucrose solutions absorbed less water than gladiolus held in water; yet, they attained a higher fresh weight than, gladiolus held in water. Cut flower longevity has been shown to be associated with maintenance of fresh weight (11, 12). It has been proposed that the increased usage of water by 8-HQC treated cut flowers is due primarily to a reduction of microbial growth in keeping solutions (6, 7). The presence >of bac teria was not assessed in this study and this aspect cannot be evaluated. However, it seems unlikely that blockage was due primarily to bacterial contamination since all solutions were changed frequently. It has been demonstrated that the life of cut roses is shortened by a nat ural stem blockage (3, 4) and that vascular blockage can be partially overcome by 8-HQC (10). Gladiolus treated with 8-HQC, sucrose, and their combination followed the same pattern for stem blockage as it did in cut roses (10). This adds support to the theory that 8-HQC has some role other than simply that of a bactericide. Although the data show that 8-HQC reduced vascular blockage and increased water absorption, the mode of action of 8-HQC is open to speculation. The influence of sucrose on cut flower life is not fully understood. Sucrose undoubtedly serves as a respiratory substrate and to a cer tain extent prevents desiccation. Sucrose also prevented stem collapse. Sucrose probably re placed the depleted natural carbohydrates and eliminated the breakdown of other organic com pounds, notably stem pectins. The additive effects of 8-HQC and sucrose on water absorption and retention are clearly demonstrated by the increased longevity and quality of gladiolus florets. LITERATURE CITED 1. Aarts, J. F. T Over de houbaarheid van snijbloemen (On the keepability of cut flowers). Mededelingen van de Landbouwhogeschool, Wagenigen, Holland 57: 1-62.

5 MAROUSKY: CUT GLADIOLUS STUDIES " 120" " Control 2 = 600 ppm 8-HQC 3 = 4% Sucrose 4» 600 ppm 8-HQC 4-4% Sucrose DAYS Fig. 2. Daily changes in fresh weight of cut 'White Friendship' gladiolus held in 8-hydroxyqu inoline citrate, sucrose, and a mixture of 8-hydroxyquinoline citrate and sucrose The keepability of cut flowers. Proc. 16th Inter. Hort. Cong. 5: Durkin, D The role of tannins in senescence of the cut rose flower. Abstracts Proc. Amer. Soc. Hort. Sci. 185: Durkin, D. and R. Kuc Vascular blockage and senescence of the cut rose flower. Proc. Amer. Soc. Hort. Sci. 89: Halevy, A. H The influence of progressive in crease in soil moisture tension on growth and water bal ance of gladiolus leaves and the development of physiologi cal indicators for irrigation. Proc. Amer. Soc. Hort. Sci. 76: Larsen, F. E. and R. W. Cromarty Micro organism inhibited by 8-hydroxquinoline citrate as related to cut flower senescence. Proc. Amer. Soc. Hort. Sci. 90: Larsen, F. E. and J. F. Scholes Effects of sucrose, 8-hydroxyquinoline citrate, and N-dimethyl amino succinamic acid on vase-life and quality of cut carnations. Proc. Amer. Soc. Hort. Sci. 87: and Effects of 8-hydroxy quinoline citrate, N-dimethyl amino succinamic acid and sucrose on vase life and spike characteristics of cut snap dragons. Proc. Amer. Soc. Hort. Sci. 89: and Effect of 8-hydroxy quinoline citrate sucrose, and Alar on vase-life and quality of cut stocks. Flor. Rev. 139(3608): 46-47, Marousky, F. J Vascular blockage, water ab sorption, stomatal opening and respiration of cut 'Better Times' roses treated with 8-hydroxyquinoline citrate and sucrose. Submitted to Jour. Amer. Soc. Hort. Sci. 11. Rogers, M Factors affecting water loss and water uptake, p In 'Living Flowers That Last A National Symposium', ed. M. Rogers. Univ. of Missouri, Columbia, Missouri. 12. Scholes, J. F Some effects of various chem icals on the post-harvest physiology fo Velvet Times roses. M. S. Thesis. Cornell University, Ithaca, New York. 13. Stoddard, E. M. and P. M. Miller Chemical control of water loss in growing plants. Sci. 137(3525):

6 414 FLORIDA STATE HORTICULTURAL SOCIETY, UJ 110 UJ 1 = Control 2 «600 ppm 8-HQC s 4% Sucrose 4-600ppm 8-HQC + 4% Sucrose Fig. 3. Spike elongation of cut 'White Friendship' gladiolus held in 8-hydroxyquinoline citrate, sucrose,and a mixture of 8-hydroxyquinoline citrate and sucrose. 14. Zelitch, I The control and mechanism of stomatal movement, p In 'Stomata and Water RelattioiiB in Plants', ed. I. Zelitch. Conn. Agr. Expt. Sta., New Haven. Conn. Bull Zentmeyer, G. A Mechanism of action of 8- hydroxyquinoline. Phytopath. 33:1121 (Abstr.).