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The Effect of Gibberellic Acid Paste on Abelmoschus esculentus Stem Elongation
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The Effect of Gibberellic Acid Paste on Abelmoschus esculentus Stem Elongation

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This was project for my general botany class.

This was project for my general botany class.

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    The Effect of Gibberellic Acid Paste on Abelmoschus esculentus Stem Elongation The Effect of Gibberellic Acid Paste on Abelmoschus esculentus Stem Elongation Document Transcript

    • The Effect of Gibberellic Acid Paste on Abelmoschus esculentus Stem Elongation
      JESYKA MELÉNDEZ, YADHIRA LUGO, ELAINE SANTIAGO
      ABSTRACT
      The aim of this investigation is to study and report the effects of gibberellic acid paste 0.5% in Lanolin (5000 ppm) on the stem elongation of A. esculentus. Two rows of plant were used to test the effect of this hormone. The plants located in the first row contained the GA application and the ones in the second row did not (these were used as a positive control in order to compare the stem elongation rate). The generous application of GA paste to the stem of the plants resulted in having no effect upon the rate of stem elongation. The rate remained constant between plants in row one and row two.
      __________________________________________
      INTRODUCTION
      Stem elongation is regulated by several hormones, gibberellins being the most influential. Gibberellins are a group of naturally occurring hormones in plants and also have an important developmental role in flowering, dormancy, sex expression, enzyme induction and senescence of leafs and fruits (Raven et al., 2005). They have been used commercially for the acceleration of these processes after their isolation in 1935 by scientists T. Yabuta and Y. Sumiki from fungal strains of Gibberella fujikuroi (Raven et al., 2005). Previous experiments conducted with gibberellin indicate the important role of this hormone in the development of plants. Amongst them, experiments conducted with Silene armeria, have proven that indeed [gibberellins are a controlling factor for stem elongation] (Cleland and Zeevaart, 1970). “Since GA regulates growth, application of very low concentrations may have a profound effect. Timing is critical: too much GA may have an opposite effect from that desired; too little may require the plant to be repeatedly treated to sustain desired levels of GA” (Riley, 1987). Experiments with gibberellins indicate that the timing if the application, concentration and responses of the different species towards GA’s are all variables when studying the effects of this hormone. This can be seen in experiments conducted with a strain of Silene armeria that was exposed to changing photoperiodical treatments. In [dark treatment of shoot tips on plants with the mature leaves kept in SD] short days [promoted elongation of immature, etiolated leaves and increased the GA1 content of shoot tips by 3 times, but did not promote stem elongation] (Talon & Zeevaart, 1992).
      The effect of GA on the plants can be highly variable depending on the plant and the type of application. This paper reports on testing the stem development of A. esculentus under the influence of a onetime application of gibberllic acid paste 0.5% in Lanolin (5000 ppm) in the tropical area of Cayey, P.R. during the month of February. Application of gibberellic acid to the stem is expected to increase elongation. The resulting data from this study will provide further insight to the effect of GA on A. esculentus stem development.
      METHODOLOGY
      Albelmoschus esculentus of the Malvaceae has been used to conduct this experiment. The growth of this plant, commonly called “Okra” or “Quimbombó”, under the influence of Gibberellic acid paste 0.5% in Lanolin (5000 ppm) was recorded over the period of 10 weeks (February 25th through May 11th). The plants were germinated in jiffy pots, fig. 1.2 & 1.2a, and then transferred to the garden. The plants were organized into four rows as can be seen in fig. 1.1; the first contained fourteen plants of which one had lost its cotyledons upon transfer to the garden.
      Fig. 1.2 The photo below shows the germinating young seedlings in the jiffy pots at day three.
      133350278765
      141605682625Fig. 1.2a The figure below shows a second image of the germinating young seedlings at day five.
      The second row contained twelve plants of which one also had lost its cotyledons upon transfer to the garden. Plants in row two were used as a positive control for growth comparison purposes. The plants on the third and fourth (seeds) rows were used for cross sectioning and measuring of normal plant development only. Gibberellic acid was applied solely to the plants on row one by completely covering the stem with the paste. The changes were observed, recorded and compared with the plants on row two (which lacked GA) over a period of 10 weeks.
      Cross sections of the plants in row three were to be done approximately every two weeks, and measurements of the growth of the plants in rows one and two were to be taken monthly.
      Fig. 1.1 The photo below displays the plant arrangement in the garden. Row one; plants exposed directly to GA by application to the stem, row two; plants used for growth comparison with plants in row one, row three; plants used for cross sectioning purposes, row four; seeds.
      13335041910RESULTS
      I. Gibberellic Acid Paste Effects
      During the ten week period of observation, morphological changes were clearly observed in the plants. The initial measurements, taken on February 25th 2009, showed that the plants in row one were generally smaller than those in row two (see figs. 1.5 and 1.3). Through the monthly measurements, this characteristic persisted and as a result the plants on row two seemed significantly taller. Although they were taller, the rate of stem elongation was kept constant between both rows of plants. The average stem elongation of plants in both rows can be seen charted in fig. 1.4. Neither plants in row one, with the GA paste application, or plants in row two displayed accelerated stem elongation. The gibberellic acid paste had no effect on the plants that had lost the cotyledons. Both the plant with the GA application and the one without it died shortly after (refer to fig. 1.3). Flower and fruit development occurred at more or less the same rate. Fruit size was generally equivalent between both rows of plants averaging between ± four inches. The following table, fig. 1.3 and chart in fig. 1.4, show the measurements taken at four periods during the plants growth.
      PlantRow 1 Feb/25/09Row 2 Row 1Mar/5/09Row 2Row 1Apr/15/09Row 2Row 1May/11/09Row 2114 cm13 ½ cm17 cm15 cm23 cm24 cm34 cm23 cm28 ½ cm4 ½ cm*12 cm*****19 cm*****34 cm*****314cm14 ½ cm16 cm16 cm22 cm18 cm28 cm36 cm411 cm15 cm11 ½ cm16 cm15 cm25 cm34 cm49 cm59 cm11 ½ cm11 ½ cm14 cm18 cm22 cm32 cm44 cm65 cm12 ½ cm6 ½ cm14 cm12 cm18 cm18 cm39 cm79 cm15 cm11 cm18 cm17 cm23 cm18 cm47 cm812 cm12 cm15 cm14 cm24 cm22 cm42 cm43 cm915 cm14 ½ cm16 ½ cm16 cm21 cm23 cm30 cm43 cm106 cm11 cm8 cm13 cm17 cm17 cm45 cm33 cm1111 cm10 cm11 cm12 cm19 cm22 cm44cm49 cm1214 cm14 cm 16 ½ cm17 cm22 cm24 cm40 cm44cm1313 cm--------15 cm--------19 cm--------38 cm--------145 cm*--------*****--------*****--------*****--------
      Fig. 1.3 Raw Data. The table above contains the stem length measurement recorded throughout a period of 10 weeks. Asterisks (*) indicate the plants who suffered cotyledon loss and the lines (----) indicate absence of plants. A steady average increase in stem length was observed.
      19050475615Fig. 1.5. The image below presents a photo of the plants in rows one and two. It can be observed the overall larger size of plants in row two when compared to those in row one.
      Fig. 1.4 Average Stem Elongation Rate. The measurements used in the chart above are an average of all the measurements taken from the plants in each of the rows monthly and then subtracted from the previous to indicate the actual rate. Blue line: plants in row one (GA applied), red line: plants in row two (no GA applied).It is clearly visible that both plants maintained the same growth rate although those in row one were generally smaller.
      RESULTS
      II. Cross Sections and Measurements
      The plants in row three and four were used for cross sectioning and measuring in order to study tissue development and maturation throughout the weeks. They were used as a control to study normal development. Cross sections were created from the stems, roots, leaf and fruit of the plants in five occasions (with exception of the fruit); more or less every two weeks. The plants were also measured and weight to identify distribution of energy. The following figures present the data recorded.
      Fig. 1.6 Stem, Leaf & Root Growth Rate. The chart above displays the results of growth rate in each of the identified plant organs. Note that Fruit development began at weeks 11 through 14 and were removed. The fruits began to grow again at week 16.The data was acquired by subtracting each the measurements from the one previous to it in order to indicate the actual rate.
      Fig.1.7 Full Plant Growth Rate. The chart below displays the resulting growth of the okra plant under normal circumstance during a period of 18 weeks. Note that fruit development began at weeks 11 through 14 and were removed. The fruit began to grow again at week 16. The data was acquired by subtracting each the measurements from the one previous to it in order to indicate the actual rate.
      Results on stem, leaf and root growth rate, see fig 1.6, indicate adequate timing of distribution of growth amongst the different organs. At week nine, growth of all three organs can be observed. The most significant amount of this growth taking place on the stem. Weeks nine through eleven show a dramatic decrease in root and leaf growth and a halting of stem increase. At weeks eleven through fourteen, root and leaf growth are initiated while the stem remains inert. It is important to note that the first fruit production took place between weeks eleven and fourteen. The fruits were removed and the growth of the plant again took place. The investing of energy in the new fruit organ slows the growth of the remaining organs (leaves, roots and stem). This explains the halting of the overall growth of the plant (see fig. 1.7). At week fourteen, leaf production is at its highest point but decreases as week sixteen approaches and stem and leaf growth are increased. Fruit production is noted once again approaching week sixteen (they are removed) causing plant growth to decrease through weeks sixteen and eighteen.
      Results using weight as the growth indicating factor display a more or less continuous weight gain (see fig. 1.9). Although all organs always showed some sort of increase, the root system was always kept with the lowest rate while the stem and leaves took in the most amount of energy. During the fruit producing weeks (weeks eleven through fourteen and sixteen) the organ weight gain is steadied. This indicates that the largest percentage of energy is being invested towards fruit production and away from the rest of the organs (see fig. 1.8). When analyzing the weight data, it is clear that growth never stops although it may decrease dramatically. But, when analyzing the data recorded from the growth in length (see fig. 1.6), it shows a halting of growth. The most likely explanation for this contradiction of results could be that growth is never halted, it is only decreased to such an extent that is has no measurable effect on the length of the organs.
      The data recorded on fig. 1.8 clearly shows that during the fruit development period of plant, the largest amount of energy goes towards fruit and leaf production. The organ with the least amount of energy absorption is clearly the root system, followed by the stem.
      Fig.1.8 Energy Distribution. The figure below is that of a pie chart showing distribution of energy amongst organs of a fruit producing plant.
      Fig. 1.9 Organ Growth Rate (Weight). The chart below displays the results of growth rate in each of the identified plant organ using weight. Note that Fruit development began at weeks 11 through 14 and were removed. The fruits began to grow again at week 16.The data was acquired by subtracting each the measurements from the previous one in order to indicate the actual rate.
      Fig. 1.10 Full Plant Growth Rate in Weight) The chart below displays the resulting growth of the okra plant under normal circumstance during a period of 18 weeks. The dry weight is also included for comparison purposes. Note that fruit development began at weeks 11 through 14 and fruits were removed. The fruit began to grow again at week 16. The data was acquired by subtracting each the measurements from the one previous to it in order to indicate the actual rate.
      When analyzing the percentage of weight that water constituted in the plant, it was calculated to be 82% of the entire weight of the plant. The dry weight constitutes only 18% of the whole weight of the plant, meaning that the greatest weight of the plant comes from water and CO₂. This was first demonstrated in experiments conducted by Jean Baptist Van Helmont with a willow tree.
      Cross Section Photos
      Week Six
      3228975498475-76200498475Fig. 1.11a Below, root cross section photo showing primary parts. Plant at week six maturation.
      Fig. 1.11b Below, stem cross section showing primary parts. Plant at weeks six in development.
      -95253175
      Week Nine
      Fig. 1.12a Below, root cross section photo showing primary parts. Plant at week nine maturation.
      38100486410Fig. 1.12b Below, stem cross section photo showing primary parts. Plant at week nine maturation
      Week Eleven
      3152775464820Fig. 1.13a Below, leaf peal showing primary parts. Plant at eleventh week in development.
      -1047751905
      Fig. 1.13b Below, leaf peal showing primary parts. Plant at eleventh week in development.
      -5715046990
      Fig. 1.13c Stem cross section showing primary parts. Plant at eleventh week maturation.
      44450622300Fig. 1.13d Below, root cross section showing primary parts. Plant at eleventh week in development.
      Week Fourteen
      Fig. 1.14a Below, stem cross section showing primary plant parts. Plant at week fourteen development.
      -38100240030
      Fig. 1.14b Below, fruit cross section photo showing primary parts. Plant at week fourteen in development.
      47625677545Fig. 1.14c Below, root cross section showing primary parts. Plant at week fourteen in development.
      Week Eighteen
      -322897540640047625501650Fig. 1.15a Below, root cross section showing primary parts. Plant at week eighteen in development
      3249930654685Fig. 1.15b Below, stem cross section showing primary parts. Plant at week eighteen in development.
      1905083185
      Fig. 1.15c Below, leaf cross section photo showing primary plant parts. Plant at week eighteen in development.
      19050120015
      Fig. 1.16 Below, photo of okra flower. It has an acropetalous arrangement and superior ovary.
      http://www.doyletics.com/images/68okrabl.jpg
      Fig. 1.17 Below, photo of okra fruit. The fruit is made from five carples and axile placentation.
      http://botany.cs.tamu.edu/FLORA/pic1/okra439.jpg
      DISCUSSION
      GA Effects
      The GA paste application to the stem of A. esculentus plants clearly did not have a profound effect. The plants with the GA application were expected to have an accelerated rate of stem elongation. Also, the possibility of GA to have an effect on the plants in row two was considered probable due to the close exposure these plants had to the hormone. The data recorded suggested otherwise. Neither the plants with GA application (row 1) nor the ones in row two displayed profuse stem elongation. The elongation rate remained average between both rows, refer to fig. 1.2. Negative feedback could have played a role in the gibberellins synthesis that resulted in it being non effective. This is speculated due to the fact that previous experiments using pea seedlings have suggested that this negative feedback mechanism has an important role in the regulation of GA 20-ox and GA 3ᵝ-hy mRNA which are required for the production of the active GA (Ait-Ali et al., 1999). It is also possible that application to the stem is ineffective and the application of the GA to other parts of the plant could have the expected results. Another possible explanation would be that even though the Vaseline remained on the stem throughout the ten weeks, the GA could have degraded before it could be effective.
      The plants did not seem, visibly, to acquire any characteristics of the ga1 mutants that take place when there is inadequate GA synthesis as a result of under or over exposure to the hormone (Raven et al., 2005). Therefore, it is assumed that the GA was simply inactive, not that there was an enzyme or pathway malfunction, allowing the plants to assume their natural course. This renders the first theory unlikely due to the fact that in the case of negative feedback, visual side effects would have been present.
      The reasons for this apparently non functional effect of the GA can only be speculated. Further studies need to be conducted in order to assure that indeed the GA was inactive and why.
      Cross Sections
      Cross sectioning of the plant organs displayed normal morphological development as was expected from the control plants. Weeks six through nine show normal development of all the primary parts such as; xylem and phloem, vascular cambium, a premature cork, trichomes and starch granules. Further development and maturation of tissues can be seen as the weeks progress (see figs. 1.11 through 1.15).
      LITERATURE CITED & REFERENCES
      Ait-Ali, T., Frances, S., Weller, J., Reid, J., Kendrick, R. and Kamiya Y. 1999. Regulation of Gibberellin 20-oxidase and Gibberellin 3ᵝ- Hydroxylase Transcript Accumulation during De-Etiolation of Pea Seedlings. Plant Phisiology 122: 783-791
      Berrios E., P.R. 2009. Personal communication.
      Cleland, C. and Zeevaart, J. 1970. Gibberellins in Relation to Flowering and Stem Elongation in the Long day Plant Silene armeria. Plant Phisiology 46(3): 392-400
      Raven, Evert and Eichhorn. 2005. Biology of Plants. Freeman. New York. pp. 613-614.
      Riley, J. 1987. Gibberellic Acid for Fruit Set and Seed Germination. CRFG Journal 19: 10-12
      Talon, M. and Zeevaart, J. 1992. Stem Elongation and Changes in the levels of Gibberellins in Shoots and Tips Induced by Differential Photoperiodic Treatments in the long-day plant Silene armeria. Planta Journal 188(4): 457-461