SAFETY AND EFFICIENCY OF XYLEM WATER TRANSPORT IN TWO CASHEW (Anacardium occidentale L.) STRAINS AT THE SEEDLING STAGE

JOKO PITONO, TSUDA MAKOTO

Abstract


ABSTRACT
As cashew trees are grown by transplanting seedlings, the seedling
often suffers from drought damaged due to prolonged dry season. Previous
study found that the ability to maintain water transport in xylem related to
drought resistant character. To determine whether there was trade-off
between the ability to maintain water transport in xylem and an efficiency
of water transport, differences in xylem vulnerability to dysfunction,
hydraulic conductance, and the relationship to xylem vessel diameter were
examined in two cashew strains. The xylem vulnerability to dysfunction
was evaluated by the applied pressure which induced 50% loss of stem
hydraulic conductivity (P 50 ). The hydraulic conductance on root, stem, and
leaf were determined with High Pressure Flow Meter (HPFM). Variations
in the P 50 values were found between A3-1 and Pangkep, whereas the
values were 1.75 and 0.50 MPa, respectively. However, since there was no
difference in the hydraulic conductance and the vessel diameter, the trade-
off between the ability to maintain water transport in xylem and an
efficiency of water transport did not occur in cashew. It was suggested that
good combination of efficiency and safety of water transport enables A3-1
to strongly uptake soil water either in dry or wet season resulting in good
adaptation to drought prone environment, and the P 50 value would be
suitable parameter for evaluating drought tolerance of cashew at the
seedling stage.
Key words: cashew strain, vessel, xylem dysfunction, hydraulic
conductance, drought

ABSTRAK
Pengembangan jambu mete secara transplanting sering diikuti
cekaman kekeringan pada bibit akibat musim kering yang berkepanjangan.
Studi awal memperlihatkan bahwa kemampuan xylem mempertahankan
fungsi transportasi air merupakan karakter pertahanan penting terhadap
cekaman kekeringan. Untuk mengetahui apakah terjadi kompensasi antara
kemampuan pertahanan fungsi xylem dan tingkat efisiensi transportasi
airnya dilakukan pengujian pada aspek kepekaan fungsi xylem, hantaran
hidraulik, dan ukuran vesselnya. Kepekaan fungsi xylem ditentukan dari
nilai tekanan udara yang menyebabkan kehilangan 50% hydraulic
conductance (P 50 ). Nilai hydraulic conductance pada akar, batang, dan
daun ditentukan dengan menggunakan metode High Pressure Flow Meter
(HPFM). Hasil pengujian menunjukkan terdapat perbedaan nilai P 50
diantara dua strain jambu mete yang diuji, yakni secara berturut-turut 1,75
dan 0,50 MPa pada strain A3-1 dan Pangkep. Karena tidak disertai
perbedaan pada hydraulic conductance dan ukuran vesselnya, maka
disimpulkan tidak ditemukan nilai adanya mekanisme kompensasi antara
kemampuan pertahanan fungsi xylem dan tingkat efisiensi pengangkutan
air. Hal ini memungkinkan A3-1 tetap dapat menyerap air tanah secara
cukup, baik pada musim kering maupun musim basah, dan mampu
beradaptasi dengan baik di daerah rawan kekeringan. Dan nilai P 50 dapat
dijadikan sebagai parameter representatif untuk evaluasi toleransi bibit
jambu mete terhadap cekaman kekeringan.
Kata kunci:  strain jambu mete, vessel, fungsi xylem, hydraulic
conductance, cekaman kekeringan


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DOI: http://dx.doi.org/10.21082/jlittri.v18n4.2012.156-161

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