PERUBAHAN FISIOLOGI DAN BIOKIMIA TANAMAN BISBUL (Diospyros discolor Willd.) (EBENACEAE) AKIBAT ARTIFICIAL LIGHT AT NIGHT (ALAN)

Abstract

NURWANI RISMONA. Perubahan Fisiologi dan Biokimia Tanaman Bisbul (Diospyros discolor Willd.) (Ebenaceae)) yang Terdampak Artificial Light at Night (ALAN). Dibimbing oleh TRIADIATI, HAMIM, dan KARTIKA NING TYAS.

Tumbuhan menggunakan cahaya sebagai sumber energi dan informasi untuk respon fisiologi tumbuhan terhadap cahaya. Salah satu perubahan lingkungan alam yang paling cepat meningkat adalah lingkungan malam hari yang dihasilkan oleh cahaya buatan yang dikenal dengan istilah Artificial Light at Night (ALAN). Studi mengenai ALAN yang telah dilakukan di daerah subtropis, menunjukkan efek negatif pada laju fotosintesis, pertumbuhan, daun gugur dan metabolisme berbagai spesies tanaman. Namun, penelitian serupa di daerah tropis, khususnya di Kebun Raya Bogor (KRB), belum banyak dilakukan. Bisbul (Diospyros discolor Willd.) merupakan salah satu spesies yang tumbuh di KRB, dan memiliki nilai ekologis serta ekonomi tinggi, sehingga perlu mendapat perhatian agar bisa dimanfaatkan dengan baik. Oleh karena itu, penelitian ini bertujuan menganalisis pengaruh ALAN terhadap perubahan fisiologi dan biokimia hingga metabolit pada tanaman bisbul. Hasil panelitian diharapkan dapat menjadi dasar pertimbangan dalam penerapan ALAN di kawasan konservasi tumbuhan di daerah tropis, khususnya Kebun Raya Bogor. Penelitian ALAN pada tanaman bisbul dilaksanakan dari bulan Januari 2023 hingga Januari 2024. Pemberian perlakuan dilakukan selama 12 bulan di Pembibitan 2 KRB BRIN. Preparasi dan analisis sampel tanaman dilakukan di Laboratorium KRB BRIN, Laboratorium Departemen Biologi IPB serta Laboratorium Riset Unggulan IPB. Rancangan penelitian menggunakan rancangan petak terbagi dalam rancangan acak kelompok faktorial. Perlakuan terdiri atas tiga faktor: warna cahaya sebagai petak utama, durasi penyinaran sebagai anak petak, dan intensitas cahaya sebagai anak–anak petak. Setiap faktor perlakuan memiliki beberapa taraf. Bahan utama yang digunakan adalah bibit tanaman bisbul yang berumur 1 tahun dengan kriteria tinggi dan jumlah daun yang relatif seragam. Parameter yang diamati terdiri atas pertumbuhan, anatomi, fisiologi, dan metabolit. Data pertumbuhan yang diukur meliputi pertambahan tinggi tajuk, diameter batang, jumlah daun senesen, dan bobot kering tanaman bisbul. Pengamatan data anatomi meliputi ketebalan daun dan kerapatan stomata. Pengukuran fisiologi meliputi laju fotosintesis, konduktasi stomata dan laju transpirasi menggunakan instrumen LI–COR 6400, serta pengukuran kandungan klorofil, yang dilakukan menggunakan spektrofotometer. Profil metabolit bisbul dianalisis menggunakan LC–MS/MS. Data morfologi, anatomi, dan fisiologi dianalisis menggunakan ANOVA pada taraf kepercayaan 95% dan bila terdapat perbedaan yang nyata dilanjutkan dengan DMRT pada taraf a=5%. Data metabolomik dianalisis menggunakan program Mzmine dan MetaboAnalyst 6.0 untuk menghasilkan heatmap. Identifikasi kelompok metabolit menggunakan PubChem. Hasil penelitian menunjukkan bahwa ALAN menyebabkan perubahan pada fisiologi dan biokimia tanaman bisbul. Perubahan ritme sirkadian akibat ALAN menyebabkan pertumbuhan tanaman bisbul yang terpapar ALAN lebih lambat dibandingkan tanaman kontrol. Gangguan ini memengaruhi ekspresi gen sirkadian, mengurangi efisiensi penangkapan dan pemanfaatan energi, serta menurunkan laju fotosintesis dan pertumbuhan tanaman. Paparan ALAN juga memengaruhi diameter batang, menyebabkan daun gugur berjumlah besar terutama durasi yang panjang 6(7) dan 12(7) malam. Fenomena ini terjadi karena alokasi karbon lebih banyak diarahkan untuk mekanisme pertahanan dibandingkan untuk pertumbuhan. ALAN juga menyebabkan laju transpirasi menurun dalam kondisi pencahayaan yang berlebihan, menunjukkan adanya stres fisiologis akibat gangguan siklus alami tanaman. Perubahan ini mencerminkan pengaruh warna cahaya dan durasi penyinaran terhadap pertumbuhan tanaman. Perlakuan dengan cahaya merah menghasilkan ukuran mesofil daun paling tebal. Kerapatan stomata dan ketebalan daun juga berubah sebagai respons terhadap pencahayaan. Penyinaran ALAN dengan berbagai warna cahaya, intensitas tinggi dan durasi penyinaran 6(7) dan 12(7) malam menyebabkan penurunan konsentrasi metabolit seperti asam kafeak dan katekin, sedangkan metabolit yang mengalami peningkatan konsentrasi adalah niasinamida dan L-prolin.

NURWANI RISMONA. Physiological and Biochemical Changes in the Bisbul Plant (Diospyros discolor Willd.) (Ebenaceae) Affected by Artificial Light at Night (ALAN). Supervised by TRIADIATI, HAMIM, and KARTIKA NING TYAS

Plants utilize light not only as a source of energy but also as an environmental signal that regulates various physiological processes. One of the most rapidly increasing environmental changes in recent years is nighttime light exposure, commonly known as Artificial Light at Night (ALAN). Studies on ALAN have been extensively conducted in subtropical regions, demonstrating its negative effects on photosynthesis rates, growth, leaf senescence, and metabolism across various plant species. However, similar studies in tropical areas, including Indonesia particularly in plant conservation area such as Bogor Botanical Gardens (Kebun Raya Bogor, KRB), are still limited. Bisbul (Diospyros discolor Willd.), a species planted in KRB, has significant ecological and economic value, highlighting the need for proper management and optimal utilization. Therefore, this study aimed to analyze the effects of ALAN on physiological and biochemical changes in bisbul plant. The results are expected to serve as a basis for considering ALAN regulation and implementation in plant conservation areas in tropical regions, especially at the Bogor Botanical Gardens. Research was conducted from January 2023 to January 2024 in the Bogor Botanical Gardens, Bogor, Indonesia. Treatments were administered for 12 months at Nursery 2 of the National Research and Innovation Agency (BRIN) at KRB, Bogor. Sample preparation and analysis were carried out at the KRB BRIN Laboratory, Department of Biology Laboratory and the Advanced Research Laboratory at IPB University. The study employed a split–plot design within a factorial randomized block design. The treatments consisted of three factors: light color as the main plot, radiation duration as the subplot, and light intensity as the sub–subplot. Each factor included multiple treatment levels. The plant material used consisted of one–year–old bisbul (D. discolor Wiild.) seedlings with relatively uniform height and leaf number. Observed parameters included aspects of plant growth, anatomical characteristics, physiological responses, and metabolite profiles. Plant growth was represented by crown height increase, stem diameter, number of senescent leaves, and dry weight of bisbul plants. Anatomical observations encompassed leaf thickness and stomatal density. Gas exchange was analyzed to photosynthetic rate, stomatal conductance, and transpiration rate, using LI–COR 6400 photosynthetic analyzer instrument. Chlorophyll content was measured using a spectrophotometer. To understand metabolomic analysis were also carried out using LC–MS/MS. Anatomical, and physiological were statistically analyzed using Analysis of Variance (ANOVA) at a 95% confidence level, followed by Duncan’s Multiple Range Test (DMRT) at the 5% significance level when significant differences were observed. Metabolomic data were processed using MZmine and MetaboAnalyst 6.0 to generate heatmaps, and metabolite groups were identified using the PubChem database. The research results show that Artificial Light at Night (ALAN) induced physiological and biochemical changes in bisbul plants. Disruptions in the circadian rhythm due to ALAN exposure slowed down the growth of bisbul plants compared to control plants. This disruption affected the expression of circadian genes, reduced the efficiency of energy capture and utilization, and descreased photosynthesis rates and overall plant growth. ALAN exposure also affected stem diameter and resulted in a greater number of senescent leaves, particularly under long–duration treatments of 6(7) and 12(7) nights. This phenomenon likely occurs because carbon allocation shifted more toward defense mechanisms rather than growth processes. ALAN also caused a decrease in transpiration rate under excessive light conditions, indicating physiological stress due to disruption of the plant’s natural cycle. These changes reflect the influence of light color and exposure duration on plant growth. Treatment with red light resulted in the thickest mesophyll tissue. Stomatal density and leaf thickness also changed in response to light. Exposure to ALAN with various light colors at high intensity for 6(7) and 12(7) consecutive nights led to a decrease in the concentrations of metabolites such as caffeic acid and catechin, whereas the concentrations of niacinamide and L-proline increased.