Eksplorasi Bakteri Endofit pada Scindapsus sp. dan Kontribusinya terhadap Pertumbuhan Tanaman

Abstract

Scindapsus merupakan tanaman hias dengan potensi ekonomi besar di pasar global, membutuhkan waktu hingga 16 minggu untuk siap jual dari stek batang, sementara ketergantungan pada pupuk kimia sebagai solusi produksi cepat justru berisiko merusak kesehatan tanah dan lingkungan dalam jangka panjang. Penelitian ini menawarkan pendekatan alternatif dengan menggali potensi mikroba asli habitat tanaman: mengisolasi dan mengkarakterisasi bakteri endofit dari Scindapsus treubii 'Dark Form Black' di Hutan Gambut, Kalimantan Barat, sekaligus menguji efektivitas isolat terpilih dalam mempercepat pertumbuhan bibit sebagai pendekatan biologis yang ramah lingkungan. Bakteri endofit diisolasi dari jaringan batang, akar, dan daun tanaman sehat menggunakan metode sterilisasi permukaan dan pengenceran bertingkat. Jaringan tanaman dipotong berukuran 1–2 cm, direndam dalam alkohol 70% selama 15 detik, dilanjutkan perendaman dalam larutan NaOCl 1% selama 15 detik, kemudian dibilas 3 kali dengan akuades steril sebelum ditanam pada media TSA dan diinkubasi pada suhu ruangan selama 24–48 jam. Koloni yang tumbuh dipurifikasi dengan metode gores (streak plate) hingga diperoleh isolat tunggal. Isolat bakteri kemudian diseleksi melalui dua uji keamanan hayati, yaitu uji hipersensitivitas untuk mengeliminasi isolat bakteri yang berpontensi patogenik pada tanaman dan uji hemolisis untuk membuang isolat yang berpotensi patogenik terhadap mamalia. Selanjutnya dilakukan uji pemacu pertumbuhan, kemampuan pelarutan fosfat, produksi hormon IAA, dan uji kompatibilitas antar-isolat, serta uji terhadap perkecambahan benih cabai. Sebanyak 56 isolat bakteri endofit berhasil diperoleh dengan batang sebagai sumber terbanyak (49,1%). 18 isolat dinyatakan aman secara hayati melalui uji hipersensitivitas dan hemolisis dan seluruhnya mampu memproduksi hormon IAA (8,26–16,96 µg/mL, dengan B16 sebagai penghasil tertinggi), namun tidak satu pun isolat bakteri endofit mampu melarutkan fosfat secara in vitro. Temuan ini mengarah pada kesimpulan penting: mekanisme utama yang bekerja pada isolat endofit gambut ini adalah jalur hormonal via IAA, bukan pelarutan fosfat, konsisten dengan karakter lahan gambut asal isolat yang asam dan miskin fosfat mineral. Dua isolat terbaik, B16 dan B22, dipilih berdasarkan performa tertinggi pada uji vigor benih cabai untuk pengujian lanjutan pada bibit. Dua isolat dengan performa terbaik selanjutnya diaplikasikan pada bibit Scindapsus dalam lima perlakuan (kontrol, NPK, isolat tunggal B16, isolat tunggal B22, dan kombinasi B16+B22) dengan pengamatan pertumbuhan vegetatif, morfologi daun, anatomi daun, dan karakter perakaran selama 14 minggu. Data yang diperoleh dianalisis menggunakan ANOVA dan DMRT. Hasil aplikasi pada bibit Scindapsus menunjukkan efektivitas yang konsisten lebih unggul dibandingkan kontrol maupun NPK pada parameter jumlah daun dan jumlah ruas yang dapat menghasilkan pembentukan empat ruas 27 hari lebih cepat dibandingkan kontrol, serta panjang tajuk meningkat hingga sekitar 20 cm dibandingkan kontrol/NPK. Morfologi daun seperti panjang, lebar, dan luas daun berpengaruh nyata terutama pada B22 dan kombinasi B16+B22, dengan luas daun mencapai hampir 40 cm² dibanding kontrol/NPK yaitu 25–28 cm². Kehijauan daun (SPAD) juga berbeda nyata pada perlakuan bakteri endofit, hal ini diduga terkait perbaikan penyerapan nitrogen lewat sistem akar yang lebih berkembang, sementara panjang tangkai daun tidak dipengaruhi signifikan. Parameter anatomi daun (tebal daun total, tebal palisade, rasio palisade) tidak berbeda nyata secara statistik antar perlakuan, meskipun ada kecenderungan peningkatan tebal daun pada perlakuan bakteri endofit, hal ini diduga karena anatomi daun Scindapsus lebih dikendalikan faktor genetik dan cahaya, serta periode pengamatan yang relatif singkat. Laju pembentukan daun pada isolat B16 meningkat signifikan 4x lebih cepat dari kontrol, sementara kombinasi B16+B22 tidak berbeda nyata dari isolat tunggal. Karakter perakaran juga berbeda nyata pada B16 atau B22 dengan panjang akar lebih tinggi 4–6 cm dibandingkan kontrol/NPK, sejalan dengan tingginya produksi IAA oleh kedua isolat. Secara keseluruhan, B22 unggul pada konsistensi morfologi daun, sedangkan B16 unggul pada kecepatan pembentukan daun , hal ini menunjukkan bahwa kedua isolat menawarkan keunggulan yang saling melengkapi. Penelitian ini membuktikan bahwa inokulasi tunggal isolat endofit asli habitat B16 dan B22 adalah alternatif yang efektif dan ramah lingkungan untuk mempercepat pertumbuhan bibit Scindapsus treubii 'Dark Form Black' yang terbukti lebih unggul dari perlakuan pupuk kimia konvensional. Temuan ini membuka jalan bagi pengembangan biostimulan lokal berbasis endofit sebagai komponen produksi tanaman hias berkelanjutan. Penelitian lanjutan disarankan mencakup uji molekuler terhadap 18 isolat, khususnya B16 dan B22, untuk identifikasi dan konfirmasi hingga tingkat spesies dengan tingkat kesamaan (similarity) =99%, serta uji mekanisme lain dari kemampuan kedua isolat dalam membantu pertumbuhan maupun perlindungan tanaman. Uji efektivitas B16 dan B22 juga perlu diperluas ke spesies tanaman hias Araceae lain untuk melihat spektrum aplikasinya sebagai agen hayati, disertai uji kandungan NPK daun setelah perlakuan. Mengingat S. treubii merupakan tanaman tahunan dengan laju pertumbuhan lambat, penelitian lanjutan juga disarankan menggunakan periode pengamatan yang lebih panjang serta pengukuran laju respirasi tanaman untuk mengonfirmasi mekanisme peningkatan pertumbuhan oleh bakteri endofit ini.

Scindapsus is an ornamental plant with substantial economic potential in the global market. However, plants propagated from stem cuttings may require up to 16 weeks to reach marketable size, while reliance on chemical fertilizers as a means of accelerating production may pose long-term risks to soil health and the environment. This study proposes an alternative approach by exploring the potential of native microorganisms associated with the plant’s natural habitat. Specifically, endophytic bacteria were isolated and characterized from Scindapsus treubii ‘Dark Form Black’ collected from a peat swamp forest in West Kalimantan, and the effectiveness of selected isolates in accelerating seedling growth was evaluated as an environmentally friendly biological approach. Endophytic bacteria were isolated from the stem, root, and leaf tissues of healthy plants using surface sterilization and serial dilution methods. The plant tissues were cut into 1–2 cm sections, immersed in 70% alcohol for 15 seconds, subsequently immersed in 1% NaOCl solution for 15 seconds, and then rinsed three times with sterile distilled water before being placed on TSA medium and incubated at room temperature for 24–48 hours. The resulting colonies were purified using the streak plate method until pure isolates were obtained. The isolates were then screened through two biosafety tests: a hypersensitivity test to exclude isolates that were pathogenic to plants and a hemolysis test to exclude isolates with potential pathogenicity toward mammals. The isolates were subsequently evaluated for their plant growth-promoting characteristics, including phosphate-solubilizing ability, IAA production, inter-isolate compatibility, and their effects on chili seed germination. The two best-performing isolates were then applied to Scindapsus seedlings under five treatments: control, NPK fertilizer, single-isolate B16, single-isolate B22, and a combination of B16 and B22. Vegetative growth, leaf morphology, leaf anatomy, and root characteristics were observed over a 14-week period. The data were analyzed using analysis of variance (ANOVA) followed by Duncan’s Multiple Range Test (DMRT). A total of 56 endophytic bacterial isolates were successfully obtained, with stems serving as the most productive source tissue, accounting for 49.1% of the isolates. Eighteen isolates were confirmed to be biosafe based on the hypersensitivity and hemolysis tests. All 18 isolates were capable of producing IAA, with concentrations ranging from 8.26 to 16.96 µg/mL, and isolate B16 exhibiting the highest production. However, none of the endophytic bacterial isolates was capable of solubilizing phosphate in vitro. These findings lead to an important conclusion: the primary mechanism exhibited by the endophytic isolates originating from the peat swamp habitat is likely hormonal activity mediated by IAA rather than phosphate solubilization. This finding is consistent with the characteristics of the peat soil from which the isolates were obtained, which is acidic and poor in mineral phosphate. The two best-performing isolates, B16 and B22, were selected based on their superior performance in the chili seed vigor test for further evaluation on Scindapsus seedlings. Application of the isolates to Scindapsus seedlings consistently produced better results than both the control and NPK fertilizer treatments in terms of leaf and node number. The treatments enabled the formation of four nodes 27 days earlier than in the control treatment and increased shoot length to approximately 20 cm compared with the control and NPK treatments. Leaf morphological characteristics, including leaf length, width, and area, were significantly affected, particularly by isolate B22 and the combined B16+B22 treatment. Leaf area reached nearly 40 cm², compared with 25–28 cm² in the control and NPK treatments. Leaf greenness, as measured by SPAD values, also differed significantly among treatments receiving endophytic bacteria. This response was presumably associated with improved nitrogen uptake through a more developed root system, whereas petiole length was not significantly affected. Leaf anatomical parameters, including total leaf thickness, palisade tissue thickness, and the palisade ratio, did not differ significantly among treatments. Nevertheless, a tendency toward increased leaf thickness was observed in the treatments receiving endophytic bacteria. This pattern may be attributed to the fact that Scindapsus leaf anatomy is more strongly influenced by genetic and light-related factors, as well as to the relatively short observation period. The rate of leaf formation in the B16 treatment increased significantly, reaching approximately four times that of the control. In contrast, the combined B16+B22 treatment did not differ significantly from the single-isolate treatments. Root characteristics also differed significantly in the B16 and B22 treatments, with root lengths 4–6 cm greater than those of the control and NPK treatments. This result was consistent with the high IAA production of both isolates. Overall, B22 demonstrated superior consistency in improving leaf morphology, whereas B16 was more effective in accelerating leaf formation. These findings indicate that the two isolates offer complementary advantages. This study demonstrates that the individual inoculation of the habitat-native endophytic isolates B16 and B22 is an effective and environmentally friendly alternative for accelerating the growth of Scindapsus treubii ‘Dark Form Black’ seedlings. The bacterial treatments were shown to be superior to conventional chemical fertilizer application. These findings provide a foundation for the development of locally based, endophyte-derived biostimulants as components of sustainable ornamental plant production. Further research should include molecular analyses of the 18 isolates, particularly B16 and B22, for identification and confirmation at the species level, with a similarity threshold of =99%. Additional studies should also investigate other mechanisms through which these isolates promote plant growth and provide plant protection. The effectiveness of B16 and B22 should be evaluated in other ornamental Araceae species to determine their application spectrum as biological agents, along with analyses of leaf NPK content following treatment. Considering that S. treubii is a perennial plant with a relatively slow growth rate, future studies should use a longer observation period and include measurements of plant respiration rates to confirm the mechanisms underlying growth enhancement by these endophytic bacteria.