Perubahan Pertumbuhan, Fisiologi, dan Profil Metabolit Bibit Kelapa Sawit (Elaeis guineensis Jacq.) Asal Jambi pada Kondisi Kekeringan dan Genangan.

Abstract

Kelapa sawit (Elaeis guineensis Jacq.) merupakan salah satu komoditas perkebunan utama di Indonesia yang saat ini menjadi produsen minyak sawit terbesar di dunia. Industri ini memberikan kontribusi besar terhadap perekonomian nasional. Minyak sawit digunakan secara luas di berbagai sektor, termasuk pangan, kosmetik, dan bioenergi. Di Provinsi Jambi, kelapa sawit juga memainkan peran penting dalam pembangunan ekonomi. Kelapa sawit di lahan budidaya memerlukan air yang cukup untuk pertumbuhan dan perkembangan yang optimal. Namun, perubahan iklim global menyebabkan peningkatan suhu dan pola curah hujan yang tidak menentu yang pada akhirnya berdampak pada munculnya cekaman kekeringan dan genangan di lahan kelapa sawit. Curah hujan yang tidak teratur dan musim kemarau yang berkepanjangan dapat menyebabkan kekeringan, sedangkan hujan berlebih dapat menyebabkan genangan terutama pada lahan yang berada di dataran rendah atau dekat sempadan sungai. Kekeringan menghambat pertumbuhan tanaman, menyebabkan pengeringan daun dan menurunkan produksi buah yang pada akhirnya berdampak negatif pada hasil minyak sawit. Di sisi lain, genangan air dapat menyebabkan tanah menjadi terlalu jenuh air, mempercepat pembusukan akar, dan menghambat pertumbuhan tanaman. Perbedaan ketersediaan air dapat menyebabkan perubahan pada pertumbuhan, fisiologi, dan metabolisme tanaman. Tanaman menghasilkan metabolit sekunder dalam kondisi cekaman sebagai respon adaptif terhadap lingkungan. Oleh karena itu, analisis terhadap profil metabolit sangat penting untuk memahami respon tanaman terhadap kondisi tersebut. Penelitian ini bertujuan mengevaluasi dampak cekaman kekeringan dan genangan terhadap pertumbuhan, fisiologi, dan profil metabolit bibit kelapa sawit, serta mengidentifikasi aksesi lokal asal Jambi yang menunjukkan toleransi terhadap kedua kondisi cekaman tersebut. Lima aksesi kelapa sawit tersebut adalah Tebo (TB), Merangin (MR), Simalungun (SM), Tanjung Jabung Barat (TJB), dan Muara Jambi (MJ) terhadap dua jenis cekaman air yaitu kekeringan dan genangan. Masing-masing cekaman diterapkan selama dua, empat, dan enam minggu dengan menggunakan bibit berumur tiga bulan. Parameter yang diamati meliputi pertumbuhan (bobot segar dan kering akar, tajuk, dan total), parameter fisiologis (laju fotosintesis, transpirasi, konduktansi stomata, kandungan klorofil, karotenoid, kandungan prolina, malondialdehida, dan gula pereduksi), serta karakter anatomi akar (luas aerenkim dan jumlah akar adventif) dan laju respirasi akar khusus pada perlakuan genangan. Hasil penelitian menunjukkan bahwa durasi kekeringan dan perbedaan aksesi memengaruhi bobot segar dan kering tanaman. Aksesi SM menunjukkan performa terbaik dengan bobot segar dan kering tertinggi baik pada akar, tajuk, maupun total tanaman, serta memiliki laju fotosintesis dan kandungan klorofil paling tinggi dibanding aksesi lainnya. Selain itu, laju transpirasi, kandungan klorofil, dan karotenoid juga dipengaruhi oleh aksesi dan durasi kekeringan secara terpisah. Kandungan gula pereduksi dipengaruhi oleh interaksi antara durasi kekeringan dan aksesi. Secara umum, kekeringan menyebabkan penurunan proses fisiologi dan pertumbuhan tanaman kelapa sawit seiring meningkatnya durasi cekaman kekeringan. Analisis metabolit menunjukkan bahwa 14 senyawa metabolit meningkat pada kondisi kekeringan. Pada tanaman yang tercekam kekeringan terjadi peningkatan metabolit di daun seperti asam shikimat, indole-3-asetat, L-tirosin, citramalat, tirosin, kumarin. Metabolit pada akar yang meningkat yaitu citrat, aspartat, maltosa, eritrosa, L-prolina, nikotinat, asam fenilasetat, L-fenilalanin, citramalat. Metabolit tersebut termasuk dalam kelompok asam amino, karbohidrat, asam karboksilat, dan flavonoid. Cekaman kekeringan juga memengaruhi beberapa jalur metabolisme penting seperti siklus glioksilat, biosintesis arginin, siklus asam trikarboksilat (TCA), dan metabolisme alanin, aspartat, serta glutamat. Cekaman genangan pada bibit kelapa sawit dipengaruhi oleh aksesi dan durasi genangan. Laju fotosintesis, transpirasi, dan konduktansi stomata dipengaruhi oleh interaksi antara aksesi dan durasi genangan. Aksesi TB menunjukkan performa terbaik dengan bobot tajuk dan total tertinggi pada bobot segar dan kering, serta memiliki kandungan klorofil dan gula pereduksi yang lebih tinggi. Kandungan prolina, gula pereduksi, klorofil, dan karotenoid dipengaruhi secara terpisah oleh faktor aksesi dan durasi genangan. Genangan juga memicu peningkatan laju respirasi akar yang meningkat seiring bertambahnya durasi genangan dengan nilai lebih tinggi dibanding kontrol. Luas aerenkim dan jumlah akar adventif juga meningkat secara signifikan menunjukkan adanya respon adaptif tanaman terhadap kondisi jenuh air. Analisis metabolit pada bibit kelapa sawit TB yang tergenang selama enam minggu menunjukkan peningkatan pada tujuh metabolit di daun dan akar. Metabolit pada daun yang meningkat saat bibit kelapa sawit tergenang enam minggu ialah l-phenylalanine, maltose, dan oxoadipate. Metabolit pada akar yang mengalami peningkatan yaitu heliotrin, xantin, 3-dehidrosikimat, dan nicotinamida. Cekaman genangan diketahui juga memengaruhi beberapa jalur metabolisme pada tanaman kelapa sawit yaitu biosintesis arginin, metabolisme glioksilat dan dikarboksilat, siklus asam sitrat (TCA), metabolisme alanin, aspartat dan glutamat, biosintesis alkaloid isoquinoline dan metabolisme asam sianoamino. Analisis profil metabolit pada daun dan akar kelapa sawit yang mengalami cekaman kekeringan dan genangan menunjukkan bahwa tanaman mengaktifkan jalur metabolik yang spesifik dan berbeda sebagai respon terhadap kedua kondisi ekstrem tersebut. Pada kekeringan, tanaman lebih menekankan akumulasi senyawa seperti asam jasmonat, asam sikimat, dan L-prolina yang berperan sebagai hormon stres dan osmoprotektan. Hal ini mengindikasikan bahwa adaptasi terhadap kekeringan lebih menekankan pada regulasi osmotik dan konservasi air dengan penyesuaian metabolik yang mendukung efisiensi fisiologis untuk mengurangi kerusakan sel. Sementara itu, pada kondisi genangan, metabolit seperti L-fenilalanin, tirosin, catechin, asam kafeta, asam salisilat dan nicotinamida meningkat secara signifikan menunjukkan aktivasi jalur fenilpropanoid dan sinyal pertahanan terhadap stres oksidatif akibat hipoksia. Respon ini menunjukkan upaya tanaman dalam memperkuat struktur sel dan mempertahankan kestabilan redoks. Meskipun respon metabolit berbeda tergantung pada jenis cekaman, beberapa metabolit seperti citramalat, L-fenilalanin, dan tirosin saling berkaitan pada kedua kondisi. Hal ini menandakan peran sentral dalam reprogramming metabolik tanaman kelapa sawit. Perbedaan distribusi antara jaringan akar dan daun juga memperkuat bahwa respon adaptif tidak seragam, melainkan disesuaikan dengan fungsi masing-masing organ. Integrasi antara profil metabolit dengan data fisiologis seperti fotosintesis, konduktansi stomata, dan respirasi akar menjadi penting untuk mengidentifikasi jalur metabolik utama yang mendukung ketahanan tanaman. Temuan ini menunjukkan bahwa pendekatan metabolomik tidak hanya memperkaya pemahaman tentang mekanisme stres, tetapi juga membuka peluang pemanfaatan metabolit sebagai biomarker untuk seleksi varietas kelapa sawit yang lebih tahan terhadap kekeringan maupun genangan dan mendukung upaya adaptasi terhadap perubahan iklim secara lebih baik dan berbasis data. Bibit kelapa sawit SM menunjukkan adaptasi terbaik terhadap kekeringan berdasarkan parameter pertumbuhan dan fisiologi, sedangkan aksesi TB menunjukkan adaptasi terbaik terhadap genangan. Dengan demikian, parameter pertumbuhan dan fisiologi dapat digunakan sebagai dasar pemilihan aksesi kelapa sawit yang toleran terhadap kondisi cekaman kekeringan dan genangan air.

Oil palm (Elaeis guineensis Jacq.) is one of Indonesia's leading plantation commodities, and Indonesia is currently the world's largest producer of oil palm. The oil palm industry makes a significant contribution to the national economy. Palm oil is widely used across various sectors, including food, cosmetics, and bioenergy. In Jambi Province, oil palm also plays an important role in economic development. Oil palm cultivated in plantations requires adequate water for optimal growth and development. However, global climate change has led to rising temperatures and unpredictable rainfall patterns, which in turn have resulted in both drought and waterlogging stress in oil palm plantations. Irregular rainfall and prolonged dry seasons can lead to drought, while excessive rainfall may cause waterlogging, particularly in low-lying areas or near riparians. Drought causes growth inhibition and reduces fruit production, ultimately leading to lower palm oil yields. On the other hand, waterlogging can lead to water-saturated soil, accelerate root decay, and inhibit plant growth. Differences in water availability can influence several changes in plant morphology, physiology, and metabolism. Plants produce secondary metabolites under environmental stress as an adaptive response to the environment. Therefore, metabolite profiling is essential to understand plant responses to such conditions. This study aims to evaluate the impact of drought and waterlogging stress on the growth, physiology, and metabolite profile of oil palm seedlings, and to identify local accessions from Jambi that show tolerance to both stress conditions. The five oil palm accessions, i.e., Tebo (TB), Merangin (MR), Simalungun (SM), Tanjung Jabung Barat (TJB), and Muara Jambi (MJ), were treated against two types of water stress, namely drought and waterlogging. Each stress was applied for two, four, and six weeks using three-month-old seedlings. The observed parameters were growth (fresh and dry weight of roots, shoots, and total biomass), physiological traits (photosynthesis rate, transpiration rate, stomatal conductance, chlorophyll content, carotenoids, proline content, malondialdehyde, and reducing sugars), as well as root anatomical characteristics (aerenchyma area and number of adventitious roots) and root respiration rate, specifically under waterlogging conditions. The results showed that drought duration and accession differences significantly affected the fresh and dry weights of the plant. The SM accession demonstrated the best performance with the highest fresh and dry weights in roots, shoots, and total plant biomass, as well as the highest photosynthetic rate and chlorophyll content compared to other accessions under drought. Additionally, transpiration rate, chlorophyll, and carotenoid contents were separately influenced by both accession and drought duration. The reducing sugar content was affected by the interaction between drought duration and accession. In general, drought stress led to a decline in physiological processes and plant growth as the duration of stress increased. Metabolite analysis revealed that 14 metabolites significantly increased under drought conditions. In plants stressed by drought, there was an increase in metabolites in the leaves, such as shikimic acid, indole-3-acetate, L-tyrosine, citramalate, tyrosine, and coumarin. Metabolites that increased in the roots were citrate, aspartate, maltose, erythrose, L-proline, nicotinate, phenylacetic acid, L-phenylalanine, and citramalate. These metabolites belong to the group of amino acids, carbohydrates, carboxylic acids, and flavonoids. Drought stress also affects several important metabolic pathways such as the glyoxylate cycle, arginine biosynthesis, citric acid (TCA) cycle, and alanine, aspartate, and glutamate metabolism. Waterlogging stress parameters in oil palm seedlings were influenced by both accession and the duration of waterlogging. Photosynthesis rate, transpiration, and stomatal conductance were affected by the interaction between accession and waterlogging duration. The TB accession exhibited the best performance, with the highest fresh and dry shoot and total biomass, as well as higher chlorophyll and reducing sugar content. Proline, reducing sugar, chlorophyll, and carotenoid contents were affected separately by accession and waterlogging duration. Waterlogging also triggered an increase in root respiration rate, which rose with longer waterlogging duration and was higher than the control. The aerenchyma area and the number of adventitious roots also increased significantly, indicating an adaptive plant response to hypoxic conditions. Metabolite analysis of TB oil palm seedlings subjected to six weeks of waterlogging showed an increase in eight metabolites in both leaves and roots. Metabolites in leaves that increased when oil palm seedlings were waterlogged for six weeks were L-phenylalanine, maltose, and oxoadipate. Meanwhile, metabolites that increased in roots were heliotrine, xanthine, 3-dehydroshikimate, and nicotinamide. Waterlogging stress was also known to affect several metabolic pathways in oil palm plants, including arginine biosynthesis, glyoxylate and dicarboxylate metabolism, citric acid cycle (TCA), alanine, aspartate, and glutamate metabolism, isoquinoline alkaloid biosynthesis, and cyanoamino acid metabolism. The analysis of metabolite profiles in oil palm leaves and roots under drought and waterlogging stress showed that the plant activated distinct and specific metabolic pathways in response to these two extreme conditions. Under drought, the plant emphasized the accumulation of compounds such as jasmonic acid, shikimic acid, and L-proline, which functioned as stress hormones and osmoprotectants. This indicated that adaptation to drought primarily involved osmotic regulation and water conservation through metabolic adjustments that supported physiological efficiency and reduced cellular damage. Meanwhile, under waterlogging conditions, metabolites such as L-phenylalanine, tyrosine, catechin, caffeic acid, as well as salicylic acid and nicotinamide increased significantly, indicating the activation of the phenylpropanoid pathway and defense signaling against oxidative stress caused by hypoxia. This response demonstrated the plant's effort to reinforce cell structures and maintain redox stability. Although the metabolite responses varied depending on the type of stress, some metabolites such as citramalate, L-phenylalanine, and tyrosine appeared under both conditions, highlighting their central role in the plant's metabolic reprogramming. The differential distribution between root and leaf tissues further emphasized that adaptive responses were not uniform but rather tailored to the specific functions of each organ. Integrating metabolite profiles with physiological data such as photosynthesis, stomatal conductance, and root respiration became essential for identifying key metabolic pathways that contributed to plant resilience. These findings demonstrated that a metabolomics-based approach not only deepened the understanding of stress response mechanisms but also offered opportunities to use metabolites as biomarkers for selecting oil palm varieties with improved tolerance to both drought and waterlogging, thereby supporting more effective, data-driven adaptation strategies to climate change. SM oil palm seedlings showed the best adaptation to drought based on growth and physiological parameters, while the TB accession demonstrated the best adaptation to waterlogging. Therefore, growth and physiological parameters can be used as a basis for selecting oil palm accessions with good adaptation to drought and waterlogging conditions.