<p>ABSTRACT<br />As cashew trees are grown by transplanting seedlings, the seedling<br />often suffers from drought damaged due to prolonged dry season. Previous<br />study found that the ability to maintain water transport in xylem related to<br />drought resistant character. To determine whether there was trade-off<br />between the ability to maintain water transport in xylem and an efficiency<br />of water transport, differences in xylem vulnerability to dysfunction,<br />hydraulic conductance, and the relationship to xylem vessel diameter were<br />examined in two cashew strains. The xylem vulnerability to dysfunction<br />was evaluated by the applied pressure which induced 50% loss of stem<br />hydraulic conductivity (P 50 ). The hydraulic conductance on root, stem, and<br />leaf were determined with High Pressure Flow Meter (HPFM). Variations<br />in the P 50 values were found between A3-1 and Pangkep, whereas the<br />values were 1.75 and 0.50 MPa, respectively. However, since there was no<br />difference in the hydraulic conductance and the vessel diameter, the trade-<br />off between the ability to maintain water transport in xylem and an<br />efficiency of water transport did not occur in cashew. It was suggested that<br />good combination of efficiency and safety of water transport enables A3-1<br />to strongly uptake soil water either in dry or wet season resulting in good<br />adaptation to drought prone environment, and the P 50 value would be<br />suitable parameter for evaluating drought tolerance of cashew at the<br />seedling stage.<br />Key words: cashew strain, vessel, xylem dysfunction, hydraulic<br />conductance, drought</p><p>ABSTRAK<br />Pengembangan jambu mete secara transplanting sering diikuti<br />cekaman kekeringan pada bibit akibat musim kering yang berkepanjangan.<br />Studi awal memperlihatkan bahwa kemampuan xylem mempertahankan<br />fungsi transportasi air merupakan karakter pertahanan penting terhadap<br />cekaman kekeringan. Untuk mengetahui apakah terjadi kompensasi antara<br />kemampuan pertahanan fungsi xylem dan tingkat efisiensi transportasi<br />airnya dilakukan pengujian pada aspek kepekaan fungsi xylem, hantaran<br />hidraulik, dan ukuran vesselnya. Kepekaan fungsi xylem ditentukan dari<br />nilai tekanan udara yang menyebabkan kehilangan 50% hydraulic<br />conductance (P 50 ). Nilai hydraulic conductance pada akar, batang, dan<br />daun ditentukan dengan menggunakan metode High Pressure Flow Meter<br />(HPFM). Hasil pengujian menunjukkan terdapat perbedaan nilai P 50<br />diantara dua strain jambu mete yang diuji, yakni secara berturut-turut 1,75<br />dan 0,50 MPa pada strain A3-1 dan Pangkep. Karena tidak disertai<br />perbedaan pada hydraulic conductance dan ukuran vesselnya, maka<br />disimpulkan tidak ditemukan nilai adanya mekanisme kompensasi antara<br />kemampuan pertahanan fungsi xylem dan tingkat efisiensi pengangkutan<br />air. Hal ini memungkinkan A3-1 tetap dapat menyerap air tanah secara<br />cukup, baik pada musim kering maupun musim basah, dan mampu<br />beradaptasi dengan baik di daerah rawan kekeringan. Dan nilai P 50 dapat<br />dijadikan sebagai parameter representatif untuk evaluasi toleransi bibit<br />jambu mete terhadap cekaman kekeringan.<br />Kata kunci: strain jambu mete, vessel, fungsi xylem, hydraulic<br />conductance, cekaman kekeringan</p>
Plant hydraulic conductance measured by the high pressure flow meter in crop plants
