Seedling growth of 2 Leucaena species

Abstract

Seed of Leucaena leucocephala (Lam) Dewit variety K-8 and L. retusa Gray variety Yellow Puff were germinated in growth chambers maintained at 10, 25,30, and 35 degrees C. A fifth treatment of 30 degrees C for 13 hours followed by 25 degrees C for 11 hours was also included. Seed were monitored every 4 days for 16 days for percent germination, testa weight, cotyledon weight, hypocotyl weight and length, and radicle weight and length. Yellow Puff exhibited higher maximum germination and a higher germination rate (expressed as percent of germinable seed germinated 4 days after imbibition) than K-8. There was no temperature effect on maximum germination of K-8, while the 35 degrees C treatment substantially reduced germination in Yellow Puff. Despite faster germination, Yellow Puff seedlings elongated slower compared to K-8. Radicle/hypocotyl ratios were similar for both species across all temperatures. Due to heavier seed weight of K-8 than Yellow Puff, testa and cotyledon weights were also heavier. Rate of nutrient reserve mobilization from the tests and cotyledon increased with increasing temperature in K-8, while rate of mobilization of nutrient reserves in Yellow Puff seed declined at temperatures above 30 degrees C.