Germination Response of Ornamental Pine Seeds on a Two-Way Thermogradient Plate

Abstract

The objective of this study was to evaluate the effect of temperature on germination of Pinus tabuliformis Carrière seed, Pinus gerardiana Wall. ex D. Don and Pinus roxburghii Sarg . Seeds of three species were distributed in Petri dishes with 1% agar solution; for the first step it was placed on a 2-way Grant’s thermogradient plate (a bi-directional incubator) for a period of 28 days and during the second step in an incubator type B.O.D. also for 28 days with non-germinated seeds in the first step. This instrument allows an assessment of a wide regime of constant and alternating temperatures, resulting to 144 differe nt combinations of temperature, scheduled to the temperatures 4 °C - 40 °C. The lighting regime was 12 hours photoperiod for the two stages of the experiment. The best temperature for the germination of P. tabuliformis was 26.2 °C (minimum of 7.9°C and maximum 37.0°C) and P. roxburghii was 15.6 °C (minimum 10, 4°C and maximum 37.0°C). The seeds are neutral photoblastic. P. gerardiana showed low germination percentage (below 10%). The temperature that provided the highest germination percentage for P. tabuliformis was 26.2°C and 15.6°C for P. roxburghii .