415 417%20(woltz)


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415 417%20(woltz)

  1. 1. WOLTZ: PHOTOSYNTHESIS IN CUT-FLOWERS 415 Each shows resistance to "shot gun fungus," hand and with knowledge of other crops that (sensitivity to temperature and moisture fluctua have been hybridized to seeming perfection, sur tions), has wide upright blades with very short prising results can be expected in the future. petioles, and has both red and green plants. LITERATURE CITED Philodendron hydridization now stands at the 1. Brown, N. E., Bot. Mag. Tab. 8172. 1908. threshhold of opportunity. Years of painstaking 2. Graf, A. B., Exotics 3. Pub. Rhoers Co. 1963. detail are behind. From the multicrosses now on PHOTOSYNTHESIS IN CHRYSANTHEMUM CUT-FLOWERS1 S. S. WOLTZ2 photosynthetic effect by defoliation. While the control flowers out-lasted the defoliated flowers, Abstract this is not considered a valid measure of the effect of light on keeping quality, since the proc It was demonstrated that the photosynthetic ess of defoliation not only stops photosynthesis activity in Chrysanthemum morifolium Ram. cut- but also removes a source of chemical compounds flowers may be of considerable importance in important in metabolism. extending vase-life. Light intensities in the range The present investigation was undertaken to 50 to 400 foot candles were beneficial in terms of measure the effects of light upon the vase-life of keeping leaves green and functioning. Blossoms cut chrysanthemum flowers. A secondary objec were benefited, but to a lesser degree. Light pre tive was to determine the basic effects in terms of served photosynthetic capacity, chlorophyll con the metabolism and biochemical constituents of tent and the supply of metabolites in leaves that leaves and flowers. were lighted compared to those in the dark. The implications of photosynthesis by chrysanthe Methods and Materials mum cut-flowers are discussed. Bluechip variety (Chrysanthemum morifol Introduction ium Ram.) was harvested immediately prior to each experiment and placed in water after cut Cut-flowers are not generally credited with ting. Flowers were illuminated in the laboratory the capacity for manufacturing food when lighted using cool white fluorescent tubes. The desired or of benefiting from illumination. Consequently, range of light intensities was obtained by placing those who handle cut-flowers (growers, whole the flowers at various distances from the lights salers, florists and users) do not usually make and by shading with saran screen as required. provisions to take advantage of any benefit that Light intensity was measured with a General might result from lighting where feasible. Electric light meter model No. 80W40X16 cali Aarts (1) investigated the effect of lighting brated in foot-candles. Light intensities were 12 hours a day with light of 2000 lumen intensity measured at the average height of leaves on the on the performance of Mathiola incana, Dianthus stem. Caryophyllus and Tulipa sp. Mathiola cut-flowers Measurements of photosynthesis and respira lasted 20 days in the light but only 13 in dark tion by leaf disks were carried out in the manner ness. Dianthus lasted approximately as long in described in a previous publication (5). Chloro light as in darkness; however, the stems were phyll was determined by the method of Arnon(2). weaker and bent in darkness. Tulipa was not Anthocyanin was extracted from petals with benefited by light. An effort was made to estimate ethanol containing 1% HC1, a modification of the effect of lighting Chrysanthemum morifolium the method of Block, et ah (3) and measured by comparing the keeping quality of manually spectrophotometrically at 505 mu, the wavelength defoliated cut-flowers with control cut-flowers, of greatest light extinction. Sugars, amino acids both being lighted. The object was to remove the and oxalic acid were determined semi-quantita- tively by paper chromatography (3). lFlorida Agricultural Experiment Stations Journal Series Three experiments were performed in Decem No. 2212. 2Gulf Coast Experiment Station, Bradenton, Florida. ber, 1964 and January 1965 studying the effect of
  2. 2. 416 FLORIDA STATE HORTICULTURAL SOCIETY, 1965 Table 1. Effect of light upon leaves of chrysanthemum cut-flowers Light pH of intensity., Photosyn- Free Vase- leaf foot- thetic Respira Chloro Glu Fruc Su Oxalic amino life, homo- candles capacity*** tion**** phyll* cose* tose* crose* acid* acids* days genate 400 46 11 24 6.3 7.5 0.5 3.0 33 11+ 6.0 200 31 9 24 4.5 6.3 0,8 2.3 23 11+ 5.8 100 14 8 11 2.5 3.8 0.5 0.5 14 11 5.8 50 10 8 9 2.0 5.0 0.5 0.8 15 11 5.6 25 3 6 5 0.3 1.5 0.3 0,3 5 9 5.6 13 2 4 4 0.3 1.0 0.3 0.3 10 8 5.8 7 ** ** 0.3 0.5 0.3 0.3 6 8 5.6 0 ** ** 0.0 0.0 0.0 0.3 9 7 5.3 LSD,5% level 4 3 % Fresh weight x 10z ** Leaves too badly deteriorated for this measurement. *** Photosynthesis measured as microliters of oxygen evolved per hour per square centimeter of leaf disks with 1500 foot-candles of light at 32° C. ****0xygen consumption by leaf disks in the dark at 32a C, microliters per hour per square cen timeter. light on chrysanthemum cut-flowers. The results related to light intensity by increasing in magni for the several experiments were quite similar. A tude as the light intensity increased. Data for single, typical experiment is therefore described. chlorophyll, sugars, oxalic and amino acid con tents of leaves indicated a favorable effect of Results light in maintaining these important biochemical constituents at useful concentrations. Number of Data are presented in Table 1 showing the days of vase-life of leaves is positively correlated effects of light intensity upon the condition of with the categories of data discussed above and leaves of chrysanthemums after 11 days treat with light intensity. The pH of leaf homogenates ment as cut-flowers. Photosynthetic capacity was decreased as light intensity decreased. apparently maintained by illumination in propor Data for the effect of intensity of illumination tion to the intensity up to the highest illumina upon the flowers (Table 2) indicate that the an- tion, 400 foot-candles. Respiratory activity, as thocyanin content of petal tissue at the conclusion measured by oxygen consumption, was similarly of the experiment was greatest at the highest Table 2. Effect of light upon blossoms of chrysanthemum cut-flowers. Light Anthocy- pH of intensity, anin petal foot- optical Glucose** Fructose** Sucrose** homo- candles density* genate 400 0.29 39 25 5 5.4 200 0,28 39 21 4 5.4 100 0.24 24 19 1 5.5 50 0.18 30 20 1 5.4 25 0.14 35 19 1 5.2 13 0.16 28 19 1 5.2 7 0.12 31 19 4 5.2 0 0.11 34 17 2 5.2 *0ptical density of an extract of 1 gram petal tissue in 10 ml. volume, **%Fresh weight X 102.
  3. 3. MENNINGER: TAIWANIA—A NEW EVERGREEN 417 level of illumination and decreased proportion Comparison of the total free amino acids leads ally with decreasing light intensity. The sugar to the conclusion that they too are depleted in contents and pH of petals were not greatly the absence of adequate light. It is not apparent, influenced by degree of illumination. however, from the data at hand whether proteins In addition to the easily measurable categories were being degraded at the higher light intensi of data in Table 2, observations were made of the ties. It is likely that they were fairly well condition of flowers relative to illumination. exploited at the lower light intensities as indi Poorly illuminated flowers (13 foot-candles and cated by McNew (4). Amino acids do not, how less) had black or white centers, rather than the ever constitute a very efficient source of energy normal pink, and deteriorating peduncles unable per unit weight. to support flower heads. Vase-life of the cut-flowers in this experiment was prolonged by lighting up to the time the Discussion experimental plan called for the conclusion of the experiment. During the course of the study, The decline of photosynthetic capacity of repeated observations indicated that flowers leaves of chrysanthemum cut-flowers (Table 1) properly cared for could be maintained in useful with storage under conditions of relatively low condition three to four times as long in the light light intensity (less than 50 foot-candles) may be as in darkness. caused by the degeneration of chlorophyll under Flowers were benefited by light (Table 2) but conditions of organic nutrient stress, as well as not as much as leaves (Table 1). Anthocyanin atrophy resulting from the imbalance of regen content of petal tissue was greater under the high erative processes requiring light. The decrease in light intensity than under low; however, this con respiratory activity relative to lower light inten stituent was not reduced nearly as much as sities is interpreted as a manifestation of the chlorophyll was in the leaves relative to lack of lack of respirable substrate. light. Sugars in flowers apparently were main Contents of sugars (Table 1) are drastically tained under low light intensity at the expense of reduced in the absence of adequate light. The leaves. chrysanthemum cut-flower apparently does not LITERATURE CITED store enough carbohydrates in the leaves to meet the requirements of the inflorescences and the 1. Aarts, J. F. T. 1957. Over de houdbaarheid van snijblomen. Pub. No. 174 lab. voor Tuinbouwplantenteelt, leaves themselves for very many days. Oxalic acid, Landbouwhogeschool, Wageningen, Holland. 2. Arnon, D. I. 1949. Copper enzymes in isolated chloro- the only organic acid detected in large amounts plasts. Polyphenoloxidase in Beta vulgaris. Plant Physiol. with the aliquots applied to the paper for chroma- 24:1-15. 3. Block, R. J., E. L. Durrum and G. Zweig. 1958. tography, was affected in the same manner as Paper chromatography and paper electrophoresis. Academic Press, Inc. 710 pp. sugars by light intensity. Although the amounts 4. McNew, G. L. 1964. The ever-expanding horizons of oxalic acid found appear to be of consider for plant research. Proc. Fla. State Hort. Soc. 77 rXXVIII- able magnitude, this metabolite is rather low- 5. Woltz, S. S. and C. D. Leonard. 1964. Effect of atmospheric fluorides upon certain metabolic processes in grade as a substrate for respiration. Valencia orange leaves. Proc. Fla. State Hort. Soc. 77:9-15. TAIWANIA-A NEW EVERGREEN CONIFER FOR FLORIDA Edwin A. MENNiNGERi another tree from the Far East that may offer untold possibilities in ornamental use. A brand new evergreen tree for ornamental The name of the new tree is Taiwania crypto- landscape use in Florida is an event. The inva merioides Hayata. As its generic name suggests, sion of the Norfolk Island pine (Araucaria ex- it is a native of the island of Taiwan, formerly celsa R. Br.) thirty years ago started a craze that called Formosa. The epithet indicates that it has grown to dominate the conifer section of the looks a lot like a Cryptomeria because of its nursery industry. Now quite unheralded comes closely packed, drooping, almost tassel-like branch tips. Its foliage however, is not soft as in Cryptomeria but hard, almost harsh. l Stuart. Florida.