TANGGAPAN FISIOLOGIS KULTIVAR KEDELAI TERHADAP CEKAMAN KEKERINGAN

YATI HARYATI, Prof. Dr. Ir. Didik Indradewa,

2012 | Tesis | S2 Agronomi

Penelitian mengenai karakter fisiologis kultivar kedelai tahan kekeringan masih cukup terbatas sehingga informasi mengenai hal tersebut belum banyak diketahui. Oleh karena itu diperlukan penggalian informasi untuk menentukan karakter fisiologi yang terkait dengan ketahanan kekeringan. Tujuan penelitian ini adalah mempelajari dan mendapatkan gambaran karakter fisiologis kultivar kedelai tahan kekeringan. Penelitian dilakukan di Kebun Tridharma Fakultas Pertanian Universitas Gadjah Mada, Banguntapan, Bantul, Daerah Istimewa Yogyakarta pada Bulan Januari - Maret 2012. Penelitian dilakukan menggunakan Rancangan Acak Kelompok Lengkap Faktorial dengan tiga blok sebagai ulangan. Faktor pertama adalah kultivar kedelai, terdiri atas lima taraf yaitu : Wilis (toleran kekeringan), Tidar (toleran kekeringan), Gema (toleran kekeringan), Grobogan (peka) dan Argomulyo (peka). Faktor kedua adalah interval penyiraman terdiri dari 4 taraf yaitu : 1, 2, 4 dan 8 hari sekali. Perlakuan cekaman kekeringan dimulai pada 24 hari setelah tanam. Variabel pengamatan meliputi kadar lengas, kadar air nisbi daun, potensial air daun, aktivitas nitrat reduktase, klorofil a, klorofil b, klorofil total, kehijauan daun, laju fotosintesis, jumlah stomata, kadar prolin, lebar bukaan stomata, laju transpirasi, tingkat kelayuan, uji sensitivitas, jumlah daun, luas daun, bobot kering tajuk, bobot kering tanaman dan bobot kering biji kedelai. Hasil penelitian memberikan informasi bahwa cekaman kekeringan mengganggu karakter fisiologis kultivar kedelai, khususnya pada kultivar yang peka cekaman kekeringan seperti Argomulyo dan Grobogan. Sedangkan karakter fisiologis kultivar kedelai tahan kekeringan (Wilis, Tidar dan Gema) hanya sedikit terpengaruh oleh cekaman kekeringan. Kultivar Wilis, Tidar dan Gema lebih mampu beradaptasi pada kondisi cekaman kekeringan melalui akumulasi senyawa prolin, mengurangi lebar bukaan stomata dan laju transpirasi serta memiliki aktivitas nitrat reduktase, kadar klorofil a, b, total, kehijauan daun dan laju fotosintesis yang tinggi

The research on physiological characteristics of soybean cultivar with resistant to drought stress condition is still limited, so that information about it not widely known. Therefore, required to extract the information to determine the physiological characters associated with drought resistance. The objective of research was to determine the physiological characteristics of soybean cultivars with resistant to drought stress. The research was conducted at Tridharma Garden, Faculty of Agriculture, Gadjah Mada University, Banguntapan, Bantul, Yogyakarta in January - March 2012. The research was arranged in randomized complete block design factorial with three blocks as replication. The first factors were cultivars of soybean, namely: Willis (drought tolerant), Tidar (drought tolerant), Gema (drought tolerant), Grobogan (drought sensitive) and Argomulyo (drought sensitive). The second factors were watering interval, namely: 1, 2, 4 and 8 days. Drought stress treatment started at 24 days after planting. The observations were done on moisture content, leaf relative water content, leaf water potential, nitrate reductase activity, chlorophyll a, chlorophyll b, total chlorophyll, relative chlorophyll content, photosynthetic rate, number of stomata, proline content, width of stomatal opening, transpiration rate, wilting level, sensitivity test, number of leaves, leaf area, shoot, root and seed dry weight. The results showed that drought stress interferes with the physiological characteristics of soybean cultivars, especially to the drought stress sensitive cultivars such as Grobogan and Argomulyo. Meanwhile, the physiological characteristics of drought stress tolerant soybean cultivars (Willis, Tidar and Gema) were only slightly affected by drought stress. Wilis, Gema and Tidar cultivars able to adapt to the drought stress conditions through the accumulation of proline compounds and reducing the width of stomatal opening, transpiration rate and nitrate reductase activity. Wilis, Gema and Tidar also have higher chlorophyll a, b and total, relative chlorophyll content and photosynthetic rate when compared to Grobogan and Argomulyo.

Kata Kunci : Kultivar kedelai, cekaman kekeringan, karakter fisiologi