Ecology of seed germination of eight non-pioneer tree species from a tropical seasonal rain forest in southwest China

Abstract

We compared various aspects of the seed biology of eight non-pioneer tree species from a tropical seasonal rain forest in Xishuangbanna, SW China, that differ in time of dispersal, size and fresh seed moisture content (MC). Seeds were tested for germination under laboratory conditions after dehydration to different moisture levels and under 3.5, 10 and 30% solar irradiances in neutral-shade houses. For six species, germination was also compared in forest understory (3.5% light) and center of a forest gap (32.5% light). Under continuous dehydration over activated silica gel, 100% of seeds of four species had lost the ability to germinate after 48 h, and those of all species except Castanopsis hystrix (decreased from [90 to 30% germination) had lost the ability to germinate after 120 h. Four species did not differ in final germination percentages at the three irradiances (i.e. uniform germination). However, final germination percentages of Horsfieldia pandurifolia and Litsea pierrei var. szemaois were significantly lower in 30% than in 10 or 3.5% light, and seeds of Antiaris toxicaria and C. hystrix germinated to higher percentages in 30 and 10% than in 3.5% light. Mean time to germination (MTG) of the eight species (forest and shade house data combined) ranged from 5-5 days for Pometia tomentosa to 72-207days for L. pierrei; MTG for four species was £21 days. There was no obvious relationship between relative desiccation resistance and either time of dispersal, MTG or uniformity of germination at the three light levels, or between seed size and MC or MTG. However, the relationship between seed MC at maturity (25-60% fresh mass basis) and MC at 50% loss of seed viability (12.4-42.5%) was significant. Seven of the species fit Garwood's (Ecol Monogr 53:159-181, 1983) rapidrainy germination syndrome and one, L. pierrei, either her delayed-rainy or intermediate-dry germination syndrome. However, fresh, non-dehydrated seeds of all eight species germinated in £30 days at constant 30°C in light.

Análise Ecofisiológica De Genipa Americana L. Em Banco De Sementes Induzido

“…Segundo Fenner e Thompson (2005), as condições microambientais podem variar signifi cativamente de um ponto para outro dentro de um mesmo ambiente fl orestal. Assim, variações em iluminação, umidade e temperatura (FENNER; THOMPSON, 2005;SRI-NGERNYUANG et al, 2003;YU et al, 2008) podem ocorrer em maior ou menor intensidade entre ambientes fl orestais distintos, interferindo no comportamento germinativo de sementes de algumas espécies.…”

“…Alguns autores têm verifi cado o aparecimento da plântula na superfície do solo (emergência) como o primeiro sinal que efetiva a germinação (GONZÁLEZ-ZERTUCHE et al, 2001;YU et al, 2008). Neste estudo, em ambiente de mata ciliar, somente 30% das amostras de sementes do banco induzido apresentaram sucesso na emergência (Figura 4), verifi cando-se alta mortalidade entre a protrusão da radícula e a emergência em ambos ambientes.…”

Germination of recalcitrant Baccaurea ramiflora seeds

“…A previous study also showed no significant difference in B. ramiflora seed germination between light and dark conditions in the field 10 . Under our laboratory conditions, the seeds of B. ramiflora germinated at temperatures between 20°C and 30°C.…”

“…In tropical forests, light is one of the most important abiotic resources, and can influence the timing of seed germination 8,9 . B. ramiflora seeds shed in summer and like other species with recalcitrant seeds germinate quickly in the field independent of the light conditions 10 . Once they are shed from the parent plant, recalcitrant seeds lose viability when exposed to extreme dry or cold conditions.…”

Germinação de sementes de Maclura tinctoria (Moraceae) sob diferentes regimes térmicos influenciados pela luz

“…A luz é um fator de extrema importância na germinação e no estabelecimento de plântulas no seu habitat natural (Yu et al 2008). Sob o ponto de vista adaptativo e ecológico parece haver uma relação entre a exigência de luz e o tamanho da semente, em resposta da espécie ao habitat (Hewitt 1998).…”