EFFECTS OF TWO DIFFERENT GROWTH REGULATORS ON THE GROWTH AND WATER RELATIONS OF ACACIA MANGIUM SEEDLINGS

• Published in: Journal of tropical forest science Vol. 6; no. 4; pp. 489 - 501
• Main Authors: Abod, Sheikh Ali, Yap, S.W.
• Format: Journal Article
• Language: English
• Published: Forest Research Institute Malaysia (FRIM) 01-06-1994
• Subjects: Forest growth; Leaf area; Plant growth; Plant growth retardants; Plant roots; Plants; Seedlings; Stomatal conductance; Transpiration; Tropical forests
• ISSN: 0128-1283

Acacia mangium seedlings overgrow in size when the timing between plant production and field planting cannot be synchronized. Survival and growth of these overgrown seedlings are reported to be poor because of unfavourable root to shoot ratio resulting in desiccation during post-transplanting. This study compares the effectiveness of two different growth regulators, namely, paclobutrazol and daminozide, for controlling the growth and water relations of A. mangium seedlings with the objective of improving their post-transplanting establishment. Fourteen-week-old potted A. mangium seedlings were foliar sprayed with paclobutrazol or daminozide at concentrations of 0, 25, 50, 75, 100, 150 and 200 mg l⁻¹. Plants were measured for height and leaf area increments, transpiration and stomatal conductance at weekly intervals. They were harvested after 12 weeks for measurements of height, leaf area, number of branches, total root length, root and shoot dry weights and the ratios of total root length to leaf area and root to shoot dry weight. Both paclobutrazol and daminozide reduced root and shoot growth, root to shoot ratio, transpiration and stomatal conductance of A. mangium seedlings. The effects of the chemicals increased with increasing concentration from 25 to 200 mg l⁻¹. Weekly measurements of height and leaf area increments, transpiration and stomatal conductance revealed that the differences in values of treated plants compared to the control generally increased with time. Paclobutrazol was more potent than daminozide in affecting seedling growth and water relations, and the two chemicals differed in their effects. The results are discussed with implications for practical application. Anak benih Acacia mangium membesar berlebihan apabila pengaturan masa antara pengeluaran pokok dan penanaman di ladang tidak boleh diselaraskan. Survival dan pertumbuhan anakbenih yang telah membesar berlebihan dilaporkan tidak baik kerana pengeringan semasa pengalihan akibat daripada nisbah akar dengan pucuk yang tidak elok. Kajian ini membandingkan keberkesanan dua pengatur tumbesaran yang berlainan iaitu paklobutrazol dan daminozid untuk mengatur tumbesaran dan kaitan air anak benih A. mangium dengan objektif untuk memperbaiki kehidupan anak-anak benih tersebut selepas pengalihan. Anak benih A. mangium yang ditanam di dalam tabung dan berumur 14 minggu diberikan semburan daun dengan paklobutrazol atau daminozid pada kepekatan 0,25,50,75,100,150 dan 200 mg l⁻¹. Pertambahan dalam ketinggian dan luas daun serta transpirasi dan konduksian stornata diukur setiap minggu. Pokok-pokok dituai selepas 12 minggu untuk pengukuran ketinggian, keluasan daun, bilangan cabang, jumlah panjang akar, berat kering akar dan pucuk serta nisbah jumlah panjang akar dengan keluasan daun dan nisbah berat kering akar dengan nisbah berat kering pucuk. Kedua-dua paklobutrazol dan daminozid mengurangkan tumbesaran akar dan pucuk, nisbah akar dengan pucuk, transpirasi dan konduksian stornata anak-anak benih A. mangium. Kesan kimia-kimia tersebut bertambah dari kepekatan 25 ke 200mg l⁻¹. Pengukuran pertambahan ketinggian dan keluasan daun, transpirasi dan konduksian stornata yang dibuat setiap minggu menunjukkan bahawa perbezaan pada nilai pokok-pokok yang dirawat berbanding dengan kawalan, pada amnya, meningkat dengan masa. Paklobutrazol lebih berkesan daripada daminozid dalam mempengaruhi tumbesaran dan kaitan air anak benih dan kesan kedua-dua kimia itu berbeza. Keputusankepu tusan yang dibincangkan mengambilkira implikasi-implikasi untuk kegunaan praktikal.