Researches concerning the physiological and biochemical modifications of the gerbera flowers during storage

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1 Volume 16(1), 1-16, 212 JOURNAL of Horticulture, Forestry and Biotechnology Researches concerning the physiological and biochemical modifications of the gerbera flowers during storage Alexe Constanta 1*, Vintila M. 1, Lamureanu Gh. 2, Doltu Madalina 1 1 Research and Development Institute for Processing and Marketing of the Horticultural Products Bucharest 2 Research Station for Fruit Growing Constanta *Corresponding author. tantialexe@yahoo.com Abstract The research in this field has demonstrated that the flower senescence process is accompanied by different functional modifications of the properties of the petals cellular membranes, including permeability, enzymatic activity, capacity of absorption of the preserving solution and respiration activity. This paper presents the physiological and biological modifications which take place during the senescence process of the gerbera flowers, Cerise cultivar. The paper also illustrates the flowers behaviour during storage in water and preserving solution (with good results in pervious research) containing: sucrose 2% + 8HQC (hydroxyquinoline citrate).2% + AgNO 3,5%, dissolved in distilled water. For the experiments we used gerbera flowers harvested in June and October, two consecutive years. The presented results represent an average of the four experimental phases. The gerbera inflorescences kept in preserving solution reveal, as compared with those kept in water, the following physiological and biochemical characteristics: higher water retention capacity in ligules, lower average values of respiratory intensity and peroxide activity from ligules, higher average content of total dry substance and total glucoses in ligules, reduced growth of ligules anthocyanic pigment content. Key words water, preserving solution, Cerise cultivar Researches performed so far have demonstrated that the flower senescence process is accompanied by different functional modifications of the properties of the petals cellular membranes such as: permeability, enzymatic activity, absorption capacity of the preserving solution, respiration activity and so on. There is little information about gerbera flowers senescence, a species which is not sensitive to ethylene, such as carnations or roses. Specialised literature offers only a limited amount of data concerning the metabolic changes that occur in the inflorescences of gerbera after harvesting. The recorded data refers to dry storage, to the use of preserving solutions and to water relations [1,2,5,8]. Research has revealed some of the metabolic changes that occur in carnations [3,6] and roses [4,7]. This paper presents the physiological and biochemical modifications which take place during the senescence process of the cut gerbera flowers, Cerise cultivar, showing their behaviour in case of storage in water and in a preserving solution (which had good results in previous researches) at ambient temperature. The aim of this paper is also scientifically reinforce the previously obtained results regarding the gerbera flowers storage in preserving solution. Material and Methods The experiment was performed using gerbera flowers, propagated vegetatively, Cerise cultivar (Figure. 1), which were harvested in June and October, two years in succession, the presented results representing the average of the four stages of the experiment. The gerberas were grown under standard greenhouse conditions. 1

2 Fig. 1. Gerbera flowers, Cerise cultivar Six hours after harvesting, the stems of the flowers were cut to have an equal length of 35 centimetres and placed for storage in a laboratory, under the following conditions: temperature o C, relative humidity 7-75%, in vases with: - V1 distilled water (control); - V2 sucrose 2% + 8HQC (hydroxyquinoline citrate).2% + AgNO 3 (silver nitrate).5%, all dissolved in distilled water. During the storage period the following analyses and determinations were performed: intensity of the water absorption process; intensity of the respiration process; content in total dry substance; content in total sugars; enzymatic activity (peroxidases); content of anthocyanic pigments within the ligules. Respiration was determined on stem, ligules and disc, by means of the Fusion gas- cromatograph. Sugars were determined in fresh petals by means of the Somoguy-Nelson method, at harvest and 2, 8, 15 day after application of the preservation solution. The analyse of peroxidases was made in petals, using the specto-pfotometric method. Content of anthocyanic pigments in ligules was determinated with device Specol 2. Results The intensity of the water absorption process Research performed with Gerbera flowers stored in preserving solution with silver nitrate 2 ppm revealed that in the first five days of storage the intensity of the water absorption process is bigger as compared to the water lost through perspiration, thus determining the growth of the fresh weight as well as the quantity of water within the ligules. Therefore, the relation hydro potential hydro deficit of the ligules manifests itself according to age, resulting in a low capacity of water retention. The water balance of flowers is disrupted both by the blockage of the transporting vessels of the flowers stems as well as by the reduction of the cells capacity to retain water. For the Cerise cultivar is has been noticed that the flowers stored in water absorbed a larger amount of liquid as compared to those stored in preserving solution. The average was of 2.86 ml/flower/day, meaning 1.38 ml/1 g floral tissue/day (Table 1). The flowers stored in preserving solution absorbed only 2/7 ml/flower/day, meaning 1.9 ml/1 g floral tissue/day. 11

3 The quantity of water absorbed by Gerbera flowers, Cerise cultivar, Variant Quantity of absorbed water ml/flower/day ml/1 g tissue/day Water Preserving solution Table 1 The absorption of a larger quantity of liquid in the case of flowers stored in water can be attributed to the lower content of active osmotic substances, therefore to the reduced capacity of water retention within the ligules. It has been observed that the volume of water the Cerise cultivar absorbs grows from the day the flowers are introduced in storage until the reaching of a maximum level which coincides with the maximum value of the flowers weight. In the case of water this maximum appears after four days of storage, whereas in the case of solution it appears after six days of storage. Afterwards both the absorption process and the weight of the flowers begin diminishing. The intensity of the respiration process The intensity of the respiration process determined on different component parts of the Gerbera flowers varies according to the specific component part of the flower. The data presented in Table 2 reveal that at harvesting the highest intensity of the respiration process was determined in ligules, growing from the exterior of the inflorescence towards its centre. The intensity of the respiration process in different component part of the Gerbera flowers, Cerise cultivar, at harvesting Component part of the flower Intensity of respiration process - mg CO 2.kg. -1 h -1 External ligulate flowers Medial ligulate flowers Central ligulate flowers Disc Stem at the base of the inflorescence Stem at the middle Stem at the base Table 2 The determinations concerning the dynamics of the whole flowers of the same variety (Figure 2) reveal two aspects: a) The first aspect refers to the climacteric maximum. Thus, in the case of storage in water, the climacteric maximum was reached after eight days of storage, whereas in the case of storage in solution it was reached after eleven days. The conclusion we can draw is that the input of nutrient substrate or of inhibitory substances delays the occurrence of this maximum, thus delaying the senescence process as well. b) The second aspect is connected to the influence of the preserving solution on the respiration process. It has been noticed that the flowers stored in water recorded a higher average value of the respiratory intensity as compared to the flowers stored in preserving solution ( mg CO 2 /kg/h as compared to mg CO 2 /kg/h). 12

Intensity of respiration respiration (mg/co2/kg/h) 4 35 3 25

4 Intensity of respiration respiration (mg/co2/kg/h) Average Determination day apa water solution Fig. 2. The dynamic of the intensity of the respiration process in Gerbera flower - Cerise cultivar, The lower average value of the respiratory intensity in the case of preserving solution can be explain through the inhibitory effect of 8HQC and AgNo 3 on the flowers biosynthesis of the ethylene, as well as on other metabolic processes within the flowers that delay the senescence process. The content of total dry substance within the ligules The data presented in Figure 3 reveal the fact that the value of the content of dry substance within the ligules grows during both variants of storage. Fig. 3. The content of total dry substance within the ligules of Gerbera flowers inflorescences - Cerise cultivar, 13

5 Total sugars (g/1g) (g/1g) Comparing the average values of the content of total dry substance within the ligules of the Gerbera flowers inflorescences on both studied options, the conclusion we can draw is that flowers stored in water have a lower average content of total dry substance within the ligules (13.23%) as compared to those stored in preserving solution (14.1%). The latter have a higher value of this marker because utilising sugar in the respiratory process was reduced (due to the quantity of sugar present in the preserving solution). The content of total sugars within the ligules The initial value of the content of total sugars within the ligules of the Gerbera flowers inflorescences, the main respiratory substrate, was of 1.57g/1 g dry substance (Figure 4) Determination day 15 Average Solution Water Fig. 4. The content of total sugars within the ligules of Gerbera flowers inflorescences - Cerise cultivar, The chart reveals the fact the content of total sugars within Gerbera flowers diminishes during storage in both water and preserving solution because of the consumption during the respiratory process. The average values are higher at flowers stored in preserving solution as compared to those stored in water (1.39 g/1g dry substance as compared to 1.8 g/1g dry substance). These differences can be explained through the absorption of sucrose from the preserving solution, which ensures a more elevated content of total sugars in the inflorescences. Peroxidases activity in the ligules The obtained results, illustrated in Figure 5, highlight the fact that the average value of the peroxidases activity in the ligules was more intense at the flowers that were stored in water (356.6 U/g/min) as compared to the flowers stored in preserving solution. The higher values of the peroxidases activity in the case of storage in water is correlated with the higher intensity of the biodegradation process which takes places within the flowers in this variant, as compared to the flowers stored in preserving solution. The maximum activity of the peroxidases occurred later on in the case of the flowers stored in preserving solution as compared to those stored in water, because of the delay in the process of senescence of the flowers stored in solution. 14

6 Peroxidases activity activity (U/g min) min) Water 1Average Solution a Determination day Fig. 5. The peroxidases activity within the ligules of Gerbera flowers inflorescence - Cerise cultivar, Content of anthocyanic pigments within the ligules The colour of the Gerbera flowers inflorescence, Cerise cultivar, is mainly determined by the content of anthocyanic pigments. After twelve days of storing the flowers in distilled water the content of anthocyanic pigments grew 2.4 times as compared to the value that was determined upon harvesting (Table 3 and Figure 6). Table 3 The initial and final content of anthocyanic pigments within the ligules tissues at the Gerbera flowers inflorescences, Cerise cultivar, Storage variant Content of anthocyanic pigments mg/1g at harvest after 12 days ratio Water Solution After the same period the content of anthocyanic pigments within the flowers stored in preserving solution grew only 1.5 times. The growth of the content of anthocyanic pigments during storage determines an intensification of the inflorescence s colour, which is more pronounced in the case of flowers stored in water, where the senescence process developed more quickly, as compared to the flowers stored in preserving solution. 15

7 Preserving solution solution At harvest After twelve days Content of anthocyanic pigments (mg/1g) Water Solution Fig. 6. The content of anthocyanic pigments within the ligules tissues at the Gerbera flowers inflorescence - Cerise cultivar, Conclusions The Gerbera flowers stored in water absorbed a larger quantity of liquid as compared to those stored in preserving solution, because of the lower content of active osmotic substances and subsequently, the reduced capacity of water retention within the ligules. The intensity of the respiratory process presents earlier maximum values for the flowers stored in water (after eight days) and later for the flowers stored in preserving solution (after twelve days), because of the input of nutrient substrate and inhibitory substances in the solution which delay the occurrence of the respiratory maximum and subsequently, of the senescence process. The Gerbera flowers stored in preserving solution present in the ligules, throughout the entire storage period, more elevated values of the content of total dry substance and total sugars as compared to the flowers stored in water, because of the absorption of the sucrose in the preserving solution through the floral stems. The peroxidases activity within the ligules is more intense at flowers stored in water as compared to those stored in preserving solution and the maximum values occur later for the second variant, because of the delay in the senescence process. The content of anthocyanic pigments within the ligules of Gerbera flowers records a larger growth in flowers stored in water as compared to flowers stored in preserving solution. The content grows 2.4 times as compared to the initial value for flowers stored in water and 1.5 times at flowers stored in solution, because of the delay in the senescence process in the second case. Physiological research on Gerbera flowers stored in both water and preserving solution scientifically demonstrate the necessity of utilising the solution for the storage of Gerbera flowers. References 1. Abdel-Kader., H. Rogers, M.N Postharvest Treatment of Gerbera Jamesonii. Acta Hort., 181: Accati Garibaldi, E Parameters Influencing Gerbera Cut Flower Longevity. Acta Hort., 261: Acok, B., Nichols, R Effects of Sucrose on Water Relations of Cut Senescing, Carnation Flowers. Ann. Bot., 44: Borochov, A., Woodson, W.R Physiology and Biochemistry of Flower Petal Senescence. Hort. Rev., 11: Burzo, I., Dobrescu, A., Amariutei, A., Stanica, M The Exchange of Substances Between Some Cut Flowers and Solutions During Vase-life. Acta Hort., 45: Halevy, A.H., Mayak, S Senescence and Postharvest Physiology of Cut Flower. Part 2. Hort. Rev., 3: Larsen E.F., Scholes, J.F Effect of 8- hydroxyquinoline Sulphate Sucrose and Alar on Vaselife and Quality of Cut Stocks. Flor. Rev., 139(368):46-47; Nowak, J The effect of silver complexes and sucrose on longevity of cut gerbera inflorescence stored for different periods of time. Pr. Inst. Sad. Kwiak. Ser. B 6:

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