Biologi Reproduksi dan Metode Konservasi Benih Vatica venulosa Blume (Dipterocarpaceae)

Abstract

Vatica venulosa Blume termasuk dalam kategori critically endangered A1c ver 2.3 menurut IUCN red list sehingga memerlukan metode konservasi menggunakan benih yang bermutu dengan waktu panen yang tepat dalam upaya menurunkan status konservasinya. Biologi reproduksi, penentuan karakter fisik dan fisiologi serta metode konservasi benih V. venulosa Blume dilakukan pada Juli 2019 sampai Juli 2020 di Pusat Penelitian Konservasi Tumbuhan dan Kebun Raya-LIPI. Penelitian dilakukan melalui pengamatan terhadap morfologi bunga, perkembangan bunga, tipe penyerbukan, buah dan benih, struktur benih, penentuan hitungan awal dan akhir perkecambahan, masak fisiologi benih, kadar air kritis benih, dan metode konservasi benih secara invitro menggunakan Woody Plant Medium (WPM). V. venulosa termasuk kategori sub annual, sistem reproduksi tipe hermaprodit, tipe perbungaan berupa inflorescens. Tipe penyerbukan merupakan penyerbukan silang, struktur bunga termasuk heteromorfik, letak putik lebih tinggi/panjang dari benangsari (kategori pin), dikogami tipe protandrus, pengunjung bunga berupa serangga sejenis nimfa Thrips sp (Thysanoptera:Thripidae) dengan warna putih, ukuran 1 mm sampai 1,5 mm. Persentase bunga mekar 32,25 % – 37,93 %, bunga diserbuki 26,89 % – 29,27%, bunga gugur/mati 83,63 % – 92,92 %, kuncup bunga berhasil menjadi buah 3,63 % – 4,79 % dan pembentukan buah (fruitset) 13,17 % – 16,51 %. Buah V. venulosa termasuk kategori exalbuminus, kotiledon tersusun dari butiran pati dengan kandungan karbohidrat sebesar 42,48 %. Hitungan awal perkecambahan (first count) V. venulosa diperoleh pada 23 hari setelah semai (HSS) dan hitungan akhir (final count) pada 33 HSS. Benih V. venulosa mencapai masak fisiologi pada 101±3 hari setelah antesis (HSA) – 106±2 HSA dengan ciri buah berwarna cokelat-hijau sampai cokelat-cokelat, kadar air benih 41,42 % – 47,94 % dan pada saat tersebut memiliki daya berkecambah 78,75 % – 81,25 %. Kadar air kritis benih V. venulosa terjadi pada kadar air 38,63 % – 39,59 % dengan daya berkecambah 42,5 % – 47,5 %. Benih V. venulosa tidak mampu berkecambah saat kadar air benih sudah menurun drastis menjadi 21,57 %. Embrio V. venulosa yang didesikasi selama 10 jam berhasil dikonservasi selama 15 hari menggunakan media WPM dengan pertumbuhan embrio mencapai 70 %, pada kadar air embrio benih sebelum dikonservasi sebesar 34,1 %. Implikasi dari hasil penelitian ini adalah status konservasi V. venulosa berpotensi diturunkan mengingat tumbuhan ini sub annual dengan daya berkecambah benih 78,75 % – 81,25 % dan periode perkecambahan dari benih sampai bibit (2 daun pertama) selama 45 HSS serta konservasi in vitro; namun perlu didukung penelitian lebih lanjut mengenai periode simpan in vitro nya serta alternatif metode konservasi benih nya yang memiliki tingkat rekalsitransi yang tinggi serta daya sintas bibit di alam.

Vatica venulosa Blume is included in the critically endangered A1c ver 2.3 category according to the IUCN red list, therefore, a conservation method is required using quality seeds with the right harvest time. Reproductive biology, physical and physiological characteristics seed and its conservation methods of V. venulosa Blume was carried out in July 2019 to July 2020 at the Research Center for Plant Conservation and Botanic Gardens-LIPI. The research observed flower morphology, flower development, type of pollination, fruit and seed, seed structures, first count and final count of germination, physiologycal maturation stage, critical moisture content of seeds, and conservation methods of seeds by invitro using Woody Plant Medium (WPM). V. venulosa is categorized as sub-annuals and hermaphrodite inflorescences. A few of reproductive system aspects are cross-pollination, flower structure is heteromorphic with pin category (the location of the pistil is longer than the stamen) and dichogamy protandrous type. The flower visitors is an insect nymph of Thrips sp (Thysanoptera: Thripidae) which are white and 1 mm to 1,5 mm in size. The percentage of blooming flowers was 32,25 % to 37,93 %, 26,89 % to 29,27 % pollinated flowers, 83,63 % to 92,92 % fall/dead flowers, fruitsets 13,17 % to 16,51 %. V. venulosa fruit is included in the exalbuminous category, the cotyledons are composed a small lump resembling starch i.e. 42,48 % carbohydrates. Determination of the first count germination of V. venulosa seeds was performed at 23rd day after sowing (DAS) and the final count at 33 DAS. Physiological maturation stage of V. venulosa seeds was at 101±3 day after anthesis (DAA) to 106±2 DAA with the characteristics of brown-green to brown-brown fruit colour, seed moisture content of 41,42 % to 47,94 % and germination capacity 78,75 % to 81,25 %. The critical moisture content of V. venulosa seeds reached 38,63 % to 39,59 % having germination capacity 42,5 % to 47,5 %. When seed moisture content had decreased drastically to 21,57 %, there was no germination observed. V. venulosa embryos desiccated for 10 hours were successfully conserved for 15 days using WPM media with 70 % embryonic growth, at the moisture content of seed embryos before conservation of 34,1 %. The implication of the results of this study is that the conservation status of V. venulosa has the potential to be lowered considering that this plant is a sub annual with a seed germination capacity of 78,75 % to 81,25 % and germination period from seed to seedling (2 first leaves) for 45 DAS and in vitro conservation; however, further research needs to be supported on its in vitro storage period and alternative methods of seed conservation that a high recalcitrant rate and seedling survival in nature.