Morfologi, fisiologi dan genetik self-pruning pada tanaman jeruk nipis (Citrus x aurantiifolia (Christm.) Swingle).

Abstract

Self-pruning adalah mekanisme cell death pada cabang yang ternaungi atau sakit, yang berpotensi menguras sumber daya pohon. Hal ini biasa juga terjadi di alam pada saat pohon berada dalam tegakan yang lebat, dan tangkai bawahnya tidak menerima cukup sinar matahari untuk bertahan hidup sehingga pohon tersebut melepaskan bagian cabang tersebut. Mekanisme self-pruning ini dapat dimanfaatkan untuk mengefisiensikan biaya pemangkasan pada tanaman budidaya seperti jeruk. Hal ini disebabkan pemangkasan yang dilakukan pada budidaya tanaman jeruk nipis (Citrus x aurantiifolia (Christm.) Swingle) membutuhkan tenaga, waktu dan biaya. Tujuan dari penelitian ini adalah untuk mengetahui mekanisme yang terjadi saat tanaman mengalami self-pruning dengan pendekatan secara morfologi, fisiologi dan genetik pada tanaman jeruk nipis (Citrus x aurantiifolia (Christm.) Swingle)). Tahap penelitian meliputi percobaan asesmen kejadian self-pruning pada 7 jenis tanaman buah, pengaruh pemupukan anorganik serta zat pengatur tumbuh terhadap self-pruning, identifikasi gen yang terlibat pada kejadian self-pruning melalui tanskriptomik, pengaruh genangan terhadap kejadian self-pruning pada tanaman jeruk nipis. Data dianalisis menggunakan Duncan Multiple Range Test pada taraf kepercayaan 95%. Hasil penelitian menunjukkan bahwa : 1) secara morfologi cabang yang mengalami kejadian self-pruning baik secara alami, melalui induksi pemupukan dan zat pengatur tumbuh serta melalui penyiraman adalah cabang-cabang dengan ukuran panjang kurang dari 10 cm dan diameter yang kurang dari 2 mm, 2) tanaman yang telah mengalami self-pruning memiliki proses fisiologi seperti laju fotosintesis, konduktansi stomata dan transpirasi berjalan secara maksimal pada percobaan pengaruh pemupukan anorganik dan zat pengatur tumbuh sedangkan pada percobaan penyiraman selama aplikasi perlakuan proses fisiologi yang rendah menyebabkan tanaman mengalami kejadian self-pruning, 3) konsentrasi etilen, asam absisat serta prolin mengalami peningkatan saat perlakuan diaplikasikan sehingga kejadian self-pruning dapat terjadi, 4) RNA-seq terhadap tanaman jeruk nipis menghasilkan base clean reads 153.511.047 dimana total transkripnya sebanyak 5.914 dan diduga terdapat gen-gen yang berbeparan pada proses self-pruning seperti 1 aminocyclopropane-1-carboxylate oxydase sebagai prekusor etilen; Zeaxanthin epoxidase, cloroplastic untuk menginduksi asam absisat; Polygalacturonase berperan dalam degradasi dinding sel.

Self-pruning is a self-death mechanism on shady or diseased branches, which can potentially deplete tree resources. This is also common in nature when the tree is in a dense stand are not receiving enough sunlight to survive so the tree sheds part of the branch. This self-pruning mechanism can be used to streamline pruning production costs on cultivated plants such as oranges. This is due to the pruning carried out on the cultivation of lime (Citrus x aurantiifolia (Christm.) Swingle) plants that require energy, time and money. So that one way is to abort the leaves and branches by itself or self pruning.Self-pruning occurs due to gene expression as well as induction in the form of induction of drought, inundation, fertilization and growth regulators. The purpose of this study was to determine the mechanism that occurs when plants undergo self pruning with a transcriptomic, morphological, physiological and metabolomic approach to lime (Citrus x aurantiifolia (Christm.) Swingle) plants. In addition, to apply the self-pruning mechanism to the practice of horticultural cultivation. The research phase included an experiment to assess the occurrence of self-pruning in several types of tropical fruit plants, the effect of inorganic fertilizers and growth regulators on self-pruning, identification of genes involved in the occurrence of self-pruning through transcriptomics, the effect of inundation on self-pruning in lime trees. Data were analyzed using Duncan's Multiple Range Test at the 95% level of confidence. The results showed that: 1) morphologically the branches that experienced self-pruning both naturally, through the induction of fertilization and growth regulators and through watering were branches with a length of less than 10 cm and a diameter of less than 2 mm, 2 ) the physiological response after the plants experienced self-pruning in the experimental effect of inorganic fertilizers and growth regulators was normal while in the watering experiment, the plants showed a physiological response in the form of low rates of photosynthesis, stomatal conductance and transpiration during application, 3) concentrations of ethylene, abscisic acid and treatment proline increased when the treatment was applied so that self-pruning events could occur, 4) RNA-seq on lime plants produced 153,511,047 base clean reads where the total transcripts were 5,914 and it was suspected that there were genes that were exposed to the self-pruning process such as 1-aminocyclopropane-1-carboxylate oxidase to produce ethylene; Zeaxanthin epoxidase, cloroplastic to produce abscisic acid; Polygalacturonase plays a role in cell wall degradation.