ABSTRAK PERAN SENYAWA VOLATIL KELAPA SAWIT guineensis) DALAM PENYERBUKAN OLEH ( Elaeis guineensis) SERANGGA Elaeidobius SERANGGA Elaeidobius kamerunicus (Coleoptera : Curculionidae) DAN Thrips hawaiiensis (Thysanoptera : Thripidae) Oleh
SUCI RAHAYU NIM: 30603002
Penyerbukan kelapa sawit ( Elaeis guineensis Jacq)) oleh E. kamerunicus (Coleoptera : Curculionidae) dan T. hawaiiensis Morgan (Thysanoptera: Thripidae) merupakan interaksi mutualisme yang melibatkan tumbuhan dan serangga. Penyerbukan pada kelapa sawit tersebut disebabkan oleh metabolit sekunder volatil yang dihasilkan oleh bunga. Jenis senyawa volatil dari kelapa sawit sudah banyak diteliti, namun komposisi volatil yang merupakan karakter dari bunga jantan dan betina untuk fungsi penyerbukan belum diteliti, khususnya selama fase pembungaan. Penelitian bertujuan untuk mengkaji mekanisme penyerbukan kelapa sawit oleh E. kamerunicus dan T. hawaiiensis . Penelitian diawali dengan pengamatan pola aktivitas harian E. kamerunicus dan T. hawaiiensis , yaitu dengan menghitung jumlah kedatangan serangga ke bunga betina mekar, pengamatan dilakukan dari jam 06.00 – 17.00WIB. Deteksi sel, jaringan, dan organ kelapa sawit sebagai tempat sintesis dan akumulasi volatil dilakukan dengan pewarnaan “Neutral-Red” terhadap sayatan mikroskopik bunga dan daun kelapa sawit. Selanjutnya dilakukan analisis kualitas dan kuantitas senyawa volatil bunga jantan dan betina yang dilepaskan selama fenologi. Isolasi senyawa volatil dilakukan dengan menggunakan teknik jebak dalam kantung Nalophan (porapack Q), dilanjutkan dengan ekstraksi dan kemudian analisis dengan GC-MS. Setelah diketahui jenis komponen volatil kelapa sawit, masing-masing senyawa volatil diuji efektivitasnya dalam menarik E. kamerunicus dan T. hawaiiensis menggunakan metoda olfactometer. Pengujian efektifitas E. kamerunicus dan T. hawaiiensis, serta interaksi keduanya, terhadap penyerbukan sawit akan menunjukkan mekanisme dari peranan volatil bagi serangga penyerbuk kelapa sawit. Hal tersebut diuji secara eksperimental terhadap bunga betina sawit yang disungkup sebelum anthesis, dengan perlakuan pemberian E. kamerunicus dan T. hawaiiensis dalam jumlah yang berbeda. Berdasarkan hasil penelitian dapat disimpulkan sebagai berikut : E. kamerunicus dan T. hawaiiensis aktif pada pagi hingga sore hari, dengan puncak aktivitas E. kamerunicus pada pagi hari sekitar pukul 10.00-11.00 WIB, sedangkan T. hawaieensis puncak aktifnya pada pagi hari antara pukul 08.00-09.00 WIB dan sore
hari antara pukul 14.00-15.00 WIB. Pola aktivitas yang berbeda diduga merupakan strategi segregasi diurnal, yaitu strategi karena dua spesies polinator menempati niche yang sama, dalam hal ini bunga betina sawit anthesis. Hasil pengamatan histokimia bunga kelapa sawit pada setiap tahap perbungaan serta daun menunjukkan terdapatnya senyawa volatil. Pada umumnya senyawa volatil, merupakan turunan asam lemak, yang terwarna merah dengan pewarnaan “NeutralRed”. Sel, jaringan dan organ kelapa sawit yang bereaksi positif terhadap “NeutralRed” diduga sebagai tempat sintesis dan pelepasan volatil sawit. Disimpulkan bahwa bunga jantan mensitesis senyawa volatil pada bagian anter, polen, dan petal; bunga betina di bagian pistil, stigma, dan petal; sedangkan daun pada sel-sel parenkim dari jaringan mesofil daun. Hasil analisis GC-MS memperlihatkan bahwa jenis dan kandungan volatil pada setiap tahap perbungaan adalah sebagai berikut; bunga sawit jantan dengan tingkat kemekaran 25% dan 50% melepaskan volatil asam undekanoat (2,6834 ng/4 jam; 3,6746 ng/4 jam), asam palmitat (23,7843 ng/4jam; 52,2134 ng/4jam), estragole (24,8402 ng/4jam; 44,0498 ng/4jam), asam 2-Noninoat (0,8073 ng /4jam; 1,0566 ng/4 jam); sedangkan tingkat kemekaran 75% dan 100% menghasilkan asam palmitat (76,3367 ng/4jam; 98,000 ng/4jam), asam chloroacetic, 4 tetra decyl ester, estragol (129,0953 ng/4jam; 313,8051 ng/4 jam), dan 1-dodesin (2,6154 ng/4jam ; 11,7507 ng/4jam). Bunga betina sawit dengan tingkat kemekaran 25% , 50%, 75%, dan 100% mensintesis senyawa volatil yang sama yaitu asam palmitat (0,4742 ng/4jam; 0,5872 ng/4jam; 0,6941 ng/4jam; 0,7378 ng/4jam), farnesol (12,1468 ng/4jam; 30,8051 ng/4 jam; 36,2136 ng/4 jam; 95,8011 ng/4jam) dan squalen (6,9106 ng/4jam; 26,4210 ng/4jam; 30,7917 ng/4jam; 39,6717 ng/4jam), sedangkan pada daun didapatkan fitol dan asam kaprat. Preferensi E. kamerunicus dan T. hawaiiensis menunjukkan kesukaan yang sama, bunga jantan kelapa sawit pada tingkat kemekaran 100%, meskipun tidak menunjukkan perbedaan yang nyata terhadap pemilihan bunga betina. Ketertarikan serangga penyerbuk terhadap bunga jantan mekar 100% berhubungan dengan hasil analisis jenis dan konsentrasi senyawa volatil pada setiap tingkat kemekaran bunga. Bunga jantan dengan tingkat kemekaran 100% memiliki komposisi kompleks, selain itu juga memiliki konsentrasi senyawa volatil yang tinggi. Efektivitas E. kamerunicus dan T. hawaiiensis terhadap fertilisasi buah sawit tidak berbeda. Keduanya mampu meningkatkan buah sawit terfertilisasi, E. kamerunicus sebesar (54,8%) dan T. hawaiiensis sebanyak (43,4%). Interaksi antara E. kamerunicus dengan jumlah 30 dan T. hawaiiensis dengan jumlah 20 menunjukkan hasil tertinggi terhadap buah sawit terfertilisasi (63,5%). Ketika populasi E. kamerunicus dan T. hawaiiensis ditingkatkan dengan masing-masing berjumlah 30 ekor, buah sawit terfertilisasi mengalami penurunan menjadi 49,2%. Kata kunci : Metabolit sekunder volatil, Kelapa sawit , Elaeidobius kamerunicus, Thrips hawaiiensis
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ABSTRACT THE ROLE OF PALM OIL ( Elaeis gunieensis ) VOLATILE COMPOUNDS ON POLLINATION BY INSECTS Elaeidobius kamerunicus (Coleoptera: Curculionidae) AND Thrips hawaiiensis (Thysanoptera: Thripidae) By SUCI RAHAYU NIM : 30603002
Pollination on palm oil ( Elaeis gunieensis) by E. kamerinicus (Coleoptera : Curculionidae) and T. hawaiiensis (Thysanoptera : Thripidae) is a mutual plantinsect interaction, mediated by volatile secondary metabolite produced by flowers. There were various volatile compounds produced by palm oil which had been investigated. However, characteristic of volatile content in staminate and pistillate flowers which are significant for pollination has not been investigated. The objective of this research was to gain further insight into the nature and factors underlying pollination in oil palm by E. kamerinicus and T. hawaiiensis. Preliminary experiment of this research was an observation of daily activity pattern of E. kamerinicus and T. hawaiiensis visited pistillate flowers during anthesis, observation was conducted during 06.00. – 18.00. Detection of leaf and floral tissues responsible for synthesis and accumulation of volatile compounds were conducted microscopically by Neutral-Red staining, followed by qualitative and quantitative analysis of volatile compounds. Isolation of volatile compounds was performed by using absorbtion and dissorbtion in Nalophan bag (porrapack Q), followed by extraction and analysis by using GC-MS. The capacity of isolated volatile components of palm oil as an attractant to E. kamerinicus and T. hawaiiensis was tested by using olfactometer. The results of effectivity test of E. kamerinicus and T. hawaiiensis, as well as their interaction, on pollination could demonstrate mechanisms of volatile compounds to attract pollinator insect to visit the flower of palm oil. The effectivity test was carried out on pistillate flowers, wrapped prior to anthesis, by adding up a combination of different number of E. kamerinicus and T. hawaiiens. Result of preliminary research showed that E. kamerinicus and T. hawaiiensis were active in the morning until in the afternoon, activity peak of E. kamerinicus in the morning was at 10.00 – 11.00, while T. hawaiiensi was in the morning between 08.00 - 09.00 and in the afternoon between 14.00 - 15.00. Distinct activity pattern was considered as diurnal segregation strategy, that was a survival strategy because two pollinator species occupied the same niche (pistillate flower) during anthesis.
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Results of histochemistry observation from staminate and pistillate flowers during each inflorescence phase, as well as leaf, showed that there were positive reactions against volatile compounds derivative of fatty acid stained by Neutral-Red in flowers and leaf of oil palm. Positive reaction might indicate the site of synthesis and release of volatile oils. Volatile compounds of oil palm were released from petal, pollen, and stamen of staminate flowers whilst in pistilate flower were from petal, stigma and pistil. Mesophil tissues in leaf, on parenchim cells, also produced volatile oils. The volatile compounds produced in each inflorescence phase were as follows; staminate flowers in the level of 25% and 50% inflorescence phase discharged Undecanoic acid (2,6834 ng/4h; 3,6746 ng/4h), Palmitic acid (23.7843 ng/4h; 52.2134 ng/4h), Estragole (24.8402 ng/4h; 44.0498 ng/4h), 2-Nonynoic acid (0.8074 ng/4h; 1.0566 ng/4h); while that on the level of 75% and 100% released Palmitic acid (76.3367 ng/4h; 98.000 ng/4h), estragol (129.0953 ng/4h; 313,8051 ng/4h), and 1-dodecyne (2.6154 ng/4h; 11.7507 ng/4h). Pistillate flower in every level of inflorescence released the same volatil compounds, i.e. Palmitic acid (0.4742 ng/4h; 0.5872 ng/4h; 0.6941 ng/4h; 0.7378 ng/4h), farnesol (12.1468 ng/4h; 30.8051 ng/4h; 36.2136 ng/4 h; 95.8011 ng/4h) and squalen (6.9106 ng/4h ; 26.4210 ng/4h ; 30.7917 ng/4h; 39.6717 ng/4h), while leaf produced Phytol and Capric acid Observation of insect preference to flowers indicated that both, E. kamerunicus and T. hawaiiensis, were attracted to staminate flower at inflorescence level of 100%, although not significantly different to that of pistilate flower. Interest of pollinator to visit staminate flower was related to the result of analysis of volatile content in each inflorescence level. Staminate flower with level of inflorescence of 100% produced various volatile compounds in a high concentration. Result of the effectivity test of E. kamerunicus and T. hawaiiensis to fertilized oil palm was not significantly different. Both pollinators could increase fruit production of oil palm, E. kamerunicus by 54.8% and T. hawaiiensis by 43.4%. Interaction between E. kamerunicus (30 insects) and T. hawaiiensis (20 insects) produced the highest fertilized number of sawit fruit (63.5%). When population of E. kamerunicus and T. hawaiiensis were raised to each 30 insects, fertilized sawit fruit was reduced to 49.2%.
Key words:
Pollination, volatile secondary metabolite, oil palm , Elaeidobius kamerunicus, Thrips hawaiiensis
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