Biomass Partitioning in Corymbia Citriodora, Eucalyptus Cloeziana and E. Dunnii stock plants in response to temperature

Production of subtropical eucalypt cuttings is limited by low temperatures but nothing is known about the effects of temperature variation on biomass partitioning within eucalypt stock plants. This study determined whether changing the temperature from 28/23 °C (day/night) to 18/13, 23/18 or 33/28 °C affected the distribution of biomass among the roots, pruned hedge and cuttings of Corymbia citriodora, Eucalyptus cloeziana and E. dunnii stock plants. Root/shoot ratio was significantly higher at 18/13 °C than at 33/28 °C, with the roots of the three respective species comprising 36, 50 and 37% of total plant biomass at 18/13 °C but only 24, 27 and 18% of total plant biomass at 33/28 °C. The responses to low temperature in the Eucalyptus species were highly unusual since root/shoot ratio was elevated at 18/13 °C because of an increase in root mass. Subtropical eucalypt stock plants divert biomass production from their shoots to their roots under conditions of low temperature. Thus, sustained cutting production may require that nurseries upgrade the climatic protection for stock plants during winter conditions. Penghasilan keratan Eucalyptus subtropikal terhad oleh suhu rendah. Namun tiada apa yang diketahui tentang kesan perubahan suhu terhadap pengagihan biojisim dalam stok tanaman Eucalyptus. Kajian ini menentukan sama ada perubahan suhu daripada 28 °C/23 °C (siang/malam) kepada 18 °C/13 °C, 23 °C/18 °C atau 33 °C/28 °C memberi kesan terhadap pengagihan biojisim di kalangan akar, pucuk terpangkas dan keratan Corymbia citriodora, Eucalyptus cloeziana dan E. dunnii. Nisbah akar/pucuk lebih tinggi dengan signifikan pada 18 °C /13 °C berbanding dengan 33 °C/28 °C. Kandungan biojisim akar pada 18 °C /13 °C bagi ketiga-tiga spesies adalah masing-masing 36%, 50% dan 37% tetapi nilainya cuma 24%, 27% dan 18% pada 33 °C/28 °C. Gerak balas spesies Eucalyptus terhadap suhu rendah sangat luar biasa memandangkan nisbah akar/pucuk meningkat pada suhu 18 °C/13 °C kerana peningkatan jisim akar. Dalam keadaan suhu rendah, stok tanaman Eucalyptus subtropika mengalihkan penghasilan biojisim dari pucuk ke akar. Justeru itu, penghasilan keratan yang berkekalan mungkin memerlukan pihak tapak semaian meningkatkan perlindungan iklim bagi stok tanaman ketika musim sejuk.