Félix Pérez-García

Inhibitory effects of Artemisia herba-alba on the germination of the gypsophyte Helianthemum squamatum

The potential allelopathic role of Artemisia herba-alba has been evaluated in order to explain the community pattern of the gypsum semiarid environments of central Spain. This pattern shows a sharp ecotone between a gypsophile sparse shrubby community dominated by Helianthemum squamatum, which grows on slopes with gypsum surface crusts, and a nitrohalophilous community on the gypsum alluvial soils of piedmont dominated by Artemisia herba-alba. In order to explain this pattern, resource limitation was discarded because no significant differences in several soil parametrers, but fine earth fraction and organic matter content, had been detected in a previous study. Results confirm the inhibitory effect of aqueous extracts on the final germination percentage of scarified seeds of Helianthemum squamatum and also on the shape of the germination curves, which indicate delay of germination for the aqueous extracts. Assays with soil of the Artemisiacommunity (three types) showed that germination was strongly inhibited in soils obtained below the canopy of mature plants (litter maintained) and retarded in the other treatments. We suggest that the spatial community pattern detected in this gypsum environment and characterised by a sharp ecotone could be at least partially controlled by interference through allelopathy. This determines the excliusion of Helianthemum squamatum plants from alluvial soils.

Germination of Cistus ladanifer seeds in relation to parent material

Variability in seed germination behaviour of Cistus ladanifer L. (rockrose), a Cistaceous species widely distributed in the Mediterranean Basin, was studied in a central Spanish population under controlled conditions. No correlation between seed moisture content and germination was found. Great variability in germination was found among seeds of the population studied, not only between seeds belonging to different mother plants, but also between those collected from different capsules on the same plant. In most cases, seeds preheated at 100 °C for 30 minutes showed a significant increase in germination. This germination behaviour is related to fire regimes as this plant is a typical shrubby element of the mediterranean shrublands. Percent germination did not vary significantly after several months of seed storage at room temperature. In the same way, no difference was found in final germination percentage of seeds stored under room temperature vs. seeds stored under cold conditions.

Interpopulation variation in seed germination of five Mediterranean Labiatae shrubby species

The aim of this work was to determine seed germination characteristics of different populations of five Mediterranean Labiatae species: lavender (Lavandula stoechas), oregano (Origanum vulgare), and three species of thyme (Thymus mastichina, T. vulgaris, and T. zygis). Correlations of final germination percentage of each population with seed weight and various geographic parameters (longitude, latitude, and altitude) were studied. For each species, final germination percentages were highly variable depending on the population, ranging from 16 to 95% for Lavandula stoechas, 4-95% for Thymus zygis, 13-90% for T. vulgaris, 35-95% for T. mastichina, and 21-91% for Origanum vulgare. Similarly, germination rate (T50) varied significantly. A significant relationship between seed weight and final germination percentage was identified for the populations of L. stoechas and O. vulgare. Moreover, germination percentages correlated significantly with altitude in T. masti-china, and with longitude in O. vulgare. In ad...

GERMINATION STUDIES IN ENDEMIC PLANT SPECIES OF THE IBERIAN PENINSULA

The germinative behavior of nine plant species of the Iberian Peninsula, four of them catalogued as vulnerable or endangered by the International Union for the Conservation of Nature, was studied under controlled laboratory conditions. Most of the species studied germinated better at relatively low temperatures (15 °C and 20 °C) and, in general, high germination rates were also obtained at alternating temperatures (25/15 °C). Coronopus navasii germinated over 60% at 25 °C, the highest temperature used in this study. Lavatera oblongifolia did not surpass 20% germination under any of the conditions assayed. Seed coat scarification increased germination in Helianthemum squamatum, while seed pretreatments with hot water or sulfuric acid were effective in H. polygonoides. Less favorable results were obtained in Lavatera oblongifolia, whereas scarification was completely ineffective in Onobrychis peduncularis ssp. matritensis.

Effects of light, temperature and population variability on the germination of seven Spanish pines

Most Pinus species are obligate seeders. Thus, knowledge of germination characteristics can help in the understanding, prediction and manipulation of the regeneration and dynamics of pine forests. Seven pine species with contrasting habitat preferences and different genetic pairwise distances are present in the Iberian Peninsula and the Canary Islands: P. halepensis, P. nigra, P. pinaster, P. pinea, P. sylvestris, P. uncinata and P. canariensis . These seven pine species comprise an exceptional experimental set to test some questions related to germination traits, such as: (1) What are the effects of light and temperature on germination, taking into account interpopulation variability? (2) Is there any association of germination traits with habitat (montane versus lowland) preferences? and (3) What is the relationship between germination traits and the genetic distance between pine species? P. nigra , P. sylvestris and P. uncinata seeds showed faster germination rates. Seeds of P. nigra and P. sylvestris reached high total germination percentages in every temperature and light treatment, suggesting an opportunistic germination strategy. Unlike montane pines, lowland pines did show significant effects of temperature on germination response: final germination was higher between 15°C and 20°C than at warmer and alternating temperatures. Relatively low temperatures associated with the winter rainy season would favour germination of most of these species. Nested models showed that population variability was the main source of variation in germination response. Thus, there is no phylogenetic control of the germination response and, surprisingly, germination traits were not related to habitat preferences. As a consequence, we believe that studies of the germination characteristics of a pine species should consider different populations.

Effects of temperature and pretreatments on seed germination of nine semiarid species from NE Spain

The aim of this work was to study the seed germination characteristics, under different incubation temperatures and using different pretreatments for promoting germination, of nine species, Boleum asperum (Pers.) Desvaux, Centaurea pinnata Pau, Halopeplis amplexicaulis (Vahl.) Ung.-Sternb, Krascheninnikovia ceratoides (L.) Gueldenst, Lythrum flexuosum Lag., Microcnemum coralloides (Loscos & Pardo) Buen, Pucinellia pungens (Pau) Paunero, Thymus loscosii Willk., and Vella pseudocytisus L. subsp. paui Gomez Campo, that grow in semiarid regions of NE Spain. In eight of these species, seeds collected from several (2-9) populations were tested. Constant 15 C, 20 C, or 25 C, and alternating 15/25 C temperature regimes and 16/8 hours light/dark photoperiod conditions were used. In seeds from the different populations of Halopeplis amplexicaulis and Microcnemum coralloides, manual scarification, dry heat, and soaking in gibberellic acid solution were used as pretreatments applied for enhancing germination. Germina...

Germination ecology of the perennial Centaurium somedanum , a specialist species of mountain springs

To improve understanding of how a rare endemic species of Centaurium adapts to a specialized ecological niche, we studied the germination ecology of the mountain spring specialist, C. somedanum, a perennial species restricted to an unusual habitat for this genus. We conducted laboratory experiments with fresh seeds collected from two populations for three consecutive years, to investigate: (1) the effect of temperature and light on germination; (2) the existence of seed dormancy; and (3) inter-population and inter-annual variation in germinability. Germination occurred only in the light and at relatively low temperatures (15–228C) with no differences between constant and alternating regimes, and a significant decrease at high temperatures (258C and 308C). We found non-deep simple morphophysiological dormancy and variation in seed germinability depending on the year of seed collection.C. somedanum diverged from the common germination characteristics of the genus in: (1) its germination at lower temperatures, which contrasts with what is generally expected in wetland species but could be adaptive in the spring habitat; and (2) its morphophysiological dormancy, which we report here for the first time in the genus and which could be an adaptation to its mountain habitat.

Effects of Seed Cryopreservation and Priming on Germination in Several Cultivars of Apium graveolens

Seed germination of seven celery cultivars was studied after storage in liquid nitrogen for 1 or 30 d. Cryopreservation was also carried out on pelleted and primed seeds. None of the treatments applied reduced germination percentages. T(50) (time for germination to reach 50%) significantly decreased in Florida, Utah and Istar cultivars when priming, alone or in combination with cryopreservation, was used.

ROLE OF THE SEED COAT IN GERMINATION OF CISTUS POPULIFOLIUS L.

Effect of mechanical scarification, dry heat, hot water, and sulphuric acid on the germination behavior of Cistus populifolius L. (rockrose) was studied. Untreated seeds after 60 days of incubation germinated less than 7%. After thermal treatments, 90% germination was achieved, and sulphuric acid pretreatment gave 61% germination. Soaking in distilled water did not increase germination, but scarification of the seed coat gave 57%. Hardness and impermeability of the seed coat appear to cause deep dormancy in C. populifolius seeds.

Habitat-correlated seed germination and morphology in populations of Phillyrea angustifolia L. (Oleaceae)

The broad aim of this work was to study intraspecific variation of seed germination in Phillyrea angustifolia L. (Oleaceae), a species with a hard (water-permeable) endocarp. Germination of seeds from six different wild populations was correlated with traits related either to seed morphology or to environmental parameters. Germination of naked seeds (seeds without endocarp) at the optimum germination conditions was similar among populations and individuals, but great differences could be detected regarding the germination of seeds with endocarp both at inter- and intra-populational levels. Differences among populations could be related to climatic parameters and to morphometric variables of seeds with endocarp. A higher germination was associated with populations growing in habitats with more severe summer (higher temperature, lower precipitation and a longer drought period) and producing elongated seeds (lower Feret ratio and roundness). Moreover, seeds from eight different individuals within a population were tested independently, and great differences regarding the germination of seeds with endocarp could be detected among individuals. Our results suggest that the morphological variation found in P. angustifolia endocarp is both under strong maternal genetic control as well as influenced by environmental factors, as indicated by the high variability among individuals within one population and the significant correlation between climate variables and seed germination among populations. Finally, it is emphasized that standardization of plant propagation protocols should take into account the degree of intraspecific variation of Mediterranean species.