Efeito da luz e da temperatura na germinaˋˋo de sementes de quatro esp谷cies de Xyris L. (Xyridaceae) ocorrentes na Serra do Cip車, MG, Brasil

作者：Abreu; Maria Elizabeth Pereira; Garcia; Queila Souza

来源：Acta Botanica Brasilica, 2005.

DOI：10.1590/S0102-33062005000100014

• germination
• seed size
• positive photoblastic
• temperature
• xyris.

the xyris genus species are typical from marshy or wet soils, being quite common on minas gerais rocky fields. the objective of this study was to investigate the germinative behavior of x. cipoensis smith %26 downs, x. longiscapa a. nilsson, x. platystachia a. nilsson and x. trachyphylla mart. under different light and temperatures conditions. the germination experiments took place in germination chambers at constant temperatures of 15, 20, 25, 30, 35 and 40oc, under continuous white light and darkness, and on the alternating temperatures of 25-15, 30-15, 30-20, 35-15, 35-20 and 35-25oc, the higher temperature being in light at a 12 hours photoperiod. the four species of xyris have small and light sensitive seeds, with no germination on darkness. the seeds of x. cipoensis germinated in a strict temperature (20 to 30oc), presenting higher percentage of germination at the constant temperature of 20oc. the 15 to 30oc range were favorable to the germination of x. longiscapa, x. platystachia and x. trachyphylla seeds. these species presented low percentage of germination at 15oc. the alternating temperature did not favor the germination when compared to the constant temperatures.