Non-deep simple and deep simple morphophysiological dormancy in seeds of three species of Ilex from subtropical and tropical regions of Taiwan

Dormancy-breaking requirements and level of morphophysiological dormancy (MPD) were determined for seeds of Ilex formosana and I. uraiensis from the subtropical region, and seeds of I. rotunda from both the subtropical and tropical regions of Taiwan. We hypothesized that some Ilex species would have deep simple MPD broken by warm stratification. Germination of seeds and embryo growth was monitored at 30/20, 25/15, 20/10, 15/5 degrees C and at 25 degrees C. Seeds were cold-stratified and then incubated at 25/15 degrees C, and seeds treated with GA(3) and GA(4) were incubated at 25/15 degrees C. Fresh seeds reached 50% germination after 11-45 weeks of warm stratification. Pre-treatment with GA increased germination percentages of I. formosana and I. rotunda (tropical) but not I. uraiensis and I. rotunda (subtropical), while cold stratification did not promote germination of either species but increased the germination rate of I. rotunda (tropical). Embryo length in seeds of all species increased >= 710% prior to root emergence, and growth occurred during warm stratification. The positive response to GA and relatively short time for beginning of germination and to reach 50% germination indicate non-deep simple MPD in seeds of I. formosana and I. rotunda (tropical). The negative response to GA and long time for beginning of germination and to reach 50% germination indicate deep simple MPD in seeds of I. uraiensis and I. rotunda (subtropical). Thus, in both the subtropical and tropical regions of Taiwan, the seeds of Ilex species have non-deep simple and deep simple MPD that are broken by warm stratification. Furthermore, GA treatment increases the germination rate and percentage of Ilex seeds with non-deep simple MPD, and cold stratification promotes the seed germination rate of Ilex species with non-deep simple MPD in tropical region.

Automated summary

The dormancy-breaking requirements and level of morphophysiological dormancy (MPD) were investigated for Ilex formosana, I. uraiensis, and I. rotunda seeds from subtropical and tropical regions of Taiwan. Warm stratification was found to break the shallow simple MPD of I. rotunda seeds. The seeds reached 50% germination after 11-45 weeks of warm stratification at 25/15°C. GA treatment increased the germination rate of I. formosana and I. rotunda (tropical) seeds but had no significant effect on I. uraiensis and I. rotunda (subtropical) seeds. These findings indicate that Ilex species in subtropical and tropical regions of Taiwan have non-deep simple and deep simple MPD, which can be broken by warm stratification. Additionally, GA treatment enhances the germination rate and percentage of Ilex seeds with non-deep simple MPD, while cold stratification promotes the seed germination rate of Ilex species with non-deep simple MPD in the tropical region.