Stockplants of the tropical hardwoods Terminalia spinosa Engl, and Triplochiton scleroxylon K. Schum were grown in a controlled environment under red:far-red (R:FR) ratios ranging from 0.5-3.1. In both species, rates of shoot height increment were higher (P Terminalia spinosa, specific leaf area (SLA) was also significantly higher under lower R:FR ratios, values ranging from 175 to 210 cm<sup>2</sup> g<sup>-1</sup> in the 3.1 and 0.9 treatments respectively. No effect of R:FR ratio on SLA was recorded in Triplochiton scleroxylon. Pre-severance photo-synthetic rate, stomatal conductance and water-use efficiency were increased under the higher R:FR ratios in Terminalia spinosa, rates of photosynthesis ranging between 2.68-4.59 μmol m<sup>-2</sup> s<sup>-1</sup> in the 0.5 and 3.1 R:FR treatments respectively. Gas exchange rates of Triplochiton scleroxylon were unaffected by R:FR treatment. These contrasting responses to variation in R:FR ratio were associated with differences in rooting ability. In Terminalia spinosa, significantly higher percentage rooting was recorded in the cuttings from the 3.1 R:FR treatment than from 0.5, with values of 93.7% and 77.5% recorded respectively. R:FR ratio also affected rooting percentages of Triplochiton scleroxylon, but in this case, higher rooting percentages were recorded in the lower R:FR ratios, values ranging from 31.1–54.1% in the 3.0 and 0.5 R.FR treatments respectively. This difference in rooting response is attributed to the contrasting effects of R:FR ratio on the leaf and stem morphology of the two species. The implications of these results for stockplant management are discussed.
Annals of Applied Biology(1996) 128 (3) 541-556 [10.1111/j.1744-7348.1996.tb07113.x]
The influence of R:FR ration on the growth, photosynthesis and rooting ability of Terminalia spinosa Engl. and Triplochiton scleroxylon K. Schum