Effects of Time of Seed Maturation on Dormancy and Germination Requirements of two Important Desert Plants in the UAE

Ali El-Keblawy* and Feda A. Al-Hadad

Dept of Biology, Faculty of Science, UAE University, Al Ain, United Arab Emirates
* Presenting author: e-mail a.keblawy@uaeu.ac.ae

Abstract

The genetic and environment of mother plants during the period of seed maturation determine the level of germinability and dormancy in seeds of certain species. It has been documented that seed dormancy and germination responses vary greatly depending on time of seed development and maturation of several species. In the present study the effect of time of seed maturation on dormancy and germination requirements was determined for seeds of two plants growing in the deserts of the UAE: Cyperus conglomeratus and Sporobolus spicatus. The first species is a good forage and sand dune binder and the second could be used in rehabilitation of the degraded salty habitats. However, both the two species, especially C. conglomeratus, have innate dormancy that restricts their germination. The aim of this study was to determine the most suitable time for seed collection at which seeds have lowest possible dormancy and consequently greatest seed germination.

Seeds of S. spicatus were collected in May, August and December 2005 and seeds of C. conglomeratus were collected in August and December from two big populations around Al-Ain city, UAE. Seeds were germinated in incubators adjusted at 20, 25 and 35 ^oC in both continuous light and dark. For the limitation of seeds of August, germination was performed only on light. The results showed that germination was significantly greater in seeds of S. spicatus than those of C. conglomeratus. Seeds of S. spicatus collected in August germinated significantly greater than those collected in May and both attained greater germination than seeds of December. Seeds incubated at higher temperature (35 ^oC) germinated significantly greater than those incubated at 20 and 25 ^oC. The interaction between temperature and time of seed collection was significant indicating that seeds collected at different times respond differently to temperature during germination. Seeds of August germinated significantly greater at 20 and 25 ^oC (66.1% and 64.2%, respectively) than those of May (33.3 and 34.7%, respectively) and both attained significantly greater germination than seeds of December (16% and 9%, respectively).  At the highest temperature (35 ^oC), there was no significant difference between seeds of the three collection. Similarly, the interaction between time of seed collection and light of incubation was significant. In May collection, germination in light was significantly greater than in dark at the lower temperature (20 and 25 ^oC), but no significant difference was recorded at 35 ^oC. On the other hand, no significant difference between light and dark germination was recorded at all temperatures for December collection. The results of this experiment suggest that the best seed lot that could be used in restoring salty habitats is that of September. These seeds can germinate at a wide range of temperature and consequently could be grown at any time of the year. The results also indicate that seeds of December collection contribute more to the soil seed bank of this species. Such back rescue the persistence of this species in the unpredictable desert conditions when seedlings face repeated soil drying or any other unfavorable conditions prevent their establishment.

In C. conglomeratus, no germination took place for fresh seeds of both August and December collection at 20 and 25 ^oC. However, about 22% and 39% of September and August seeds, respectively, germinated at 35 ^oC. In order to use this species in sand dune fixation and as forage plant our results recommend dispersing the fresh seeds of both September and August at the warmer time of the year (average temperature over 30 ^oC).