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ecologia mediterranea, tome 29, fascicule 2, 2003, p. 153-164 INTERPRETING GERMINATION RESULTS BASED ON SEED SIZE, MASS AND ECOLOGICAL… ◆ Citrullus colocynthis (L.) Schrad. 12.267 3.52 43 52 70 10 13 Convolvulus lanatus Vahl 4.6 1.044 69 74 80 10 12 Deverra tortuosa (Desf.) DC 0.334 0.56 41 47 50 6 7 Cucumis prophetarum L. 4.25 8.765 43 31 32 6 9 Cyperus alopecuroides Rottb. 0.072 0.472 35 50 56 1 2 Cyperus capitatus Vand. 1.082 1.73 67 47 58 8 6 Euphorbia retusa Forssk. 0.927 2.104 45 30 42 4 4 Forsskaolea tenacissima L. 1.018 4.36 40 49 37 7 10 Juncus acutus L. 0.158 0.24 64 44 63 3 5 Helianthemum lippii (L.) Dum. 0.204 0.889 60 71 69 4 6 Hyoscyamus albus L. 0.182 0.601 54 70 74 3 5 Hyoscyamus muticus L. 0.643 1.128 56 60 62 5 7 Kickxia aegyptiaca (L.) Nabelek 0.089 0.45 43 13 38 5 4 Lotus coronopifolia Poir. 0.485 3.956 65 70 74 5 3 Lotus creticus L. 0.625 0.206 72 70 69 6 6 Lotus glaber Mill. 0.485 3.956 71 72 68 5 6 Lotus polyphyllos E.D. 4.545 8.928 81 80 89 8 7 Lycium shawii Roemer et Sch. 1.498 6.778 52 53 47 5 7 Lygos raetam (Forssk.) Heywood 20.857 13.23 67 71 64 11 15 Ononis vaginalis Vahl 2.576 8.0 70 65 63 10 6 Peganum harmala L. 0.769 5.778 32 30 42 2 4 Phagnalon barbeyanum Asch. & Schweinf. 0.103 0.433 60 42 55 2 3 Polygonum equisetiforme Sm. 0.544 2.67 63 57 54 4 6 Pergularia tomentosa L. 12.0 42.704 44 50 57 9 10 Salvia lanigera Poir. 0.653 1.44 63 37 43 6 5 Spergularia maritima (All.) Chiov. 0.094 0.39 67 37 60 5 6 Table 4. Measurements of two seed parameters, germination efficiency (%) and days of survival of the annuals and the perennials collected from different habitats. HFC: Half field capacity, FC: Field capacity size is reduced and germination percentages were nearly similar. In other words, under adequate water supply the germination percentage was 64% for the large-seeded species, Lygos raetam that was very close to the percentage attained by the small-seeded Juncus acutus (63%) and Spergularia maritima (60%). Large- seeded species, which are supposed to have more available resources (e.g. Lygos raetam, Cenchrus ciliaris, Carduus getulus and Cleome amblyocarpa), provide much chances for establishment of their seedlings to survive longer days after emergence on both Petri dishes and also in soil substrate especially under low water treatment (table 4). On the other hand, smallseeded species showed short period of persistence after emergence (e.g. Spergularia maritima, Juncus acutus and Kickxia aegyptiaca). Correlation between seed mass and seed size as well as the period of survival from emergence (table 5) revealed highly significant degree of association for annuals when their seeds are germinated at different moisture levels On the contrary, no significant correlation (p > 0.05) was noticed between neither seed mass, or size and the period of survival for perennials under shortage of water, which in turn revealed that those seeds are less sensitive to such factor than annuals. Attempts have been made to show whether there is any relation between moisture availability of the habitat and the weight and size of seeds. Catchment area, inland plateau and rocky cliffs were distinguished by the presence of coarse gravels near the soil. It was notable that a proportional increase in the seed mass was associated to the increase of moisture availability of the habitat. Pearson’s two-tailed correlation was applied on each set of data representing each habitat. Results showed positive highly significant correlations between seed size 161
162 ◆ L. M. M. BIDAK Value of correlations Seed mass Germination % Seed size Petri-dish -0.136 0.031 Half- water (HFC) 0.024 0.147 Full water (FFC) -0.063 0.096 Number of Days of survival Petri- dish for annuals 0.866** 0.470** Petri- dish for perennials 0.520* 0.371* Half-Water for annuals Half-Water for perennials and seed mass especially when water is available in the habitats (e.g. canal bank, fallow fields, wadi & catchment area). When availability of water decreased and habitats tend to be drier, no significant correlation is obtained (e.g. the inland plateau, saline depression, sand dunes and rocky cliffs). These results are confirmed by the correlation value between seed size and mass of plant species collected from the catchments areas, desert and railway roads, where occasional availability of water occurs depending on the rain or other sources. DISCUSSION 0.700** 0.194 ** Correlation is significant at the 0.01 probability level. * Correlation is significant at the 0.05 probability level. Table 5. Values of Pearson’s two-tailed correlation. 0.587** 0.348 The size and shape of the studied seeds are extremely variable. These characteristics depend on the form of the ovary, the condition under which the parent plant is grown and obviously on the species. Other factors, which determine the size and the shape of seeds, are the size of the embryo and the amount of the endosperm. Several authors (e.g. Mott, 1972; Pate & McComb, 1981) have argued that the germination events in arid and semi-arid regions are triggered by large rainfall events and so the developing seedlings may not face water stress for some time. Many species showed adaptations to ensure germination only under favorable soil moisture conditions and may have characteristics such as mucilaginous gel or hairs which improve the soil-seed contact to maximize water uptake (Pate & McComb, 1981). Habitats can be classified along a spectrum from environments permitting fast growth rate to environments permitting only slow growth rate, due to low soil nutrients or moisture or to other impediments to plant growth. Species occupying slow growth habitats tend to have naturally slow relative growth rate even when given favorable conditions (e.g. Grime, 1974, 1977; Chapin, 1980, 1991). In the present study, results of germination and growth performance of the plant species collected from the saline and inland plateau habitats revealed that seedling growth, emergence, germination and establishment of seeds were more affected than those collected from other habitats. This may be attributed to the stressful effect of the habitat and this seems to be in agreement with the finding trend suggested by Grime (1974, 1977) and Chapin (1980, 1991). Resources in the embryo and endosperm of a seed are deployed during germination to construct a seedling. Different plant species provision their seeds with different quantities of resources to support seedling establishment. Species span a range of seed mass from less than 10 -6 to more than 10 4 g (Harper, 1977). Differences across species in seed coat thickness, dispersal structures, water contents and mineral nutrient concentrations reflect a wide range in the dry mass of resources provided by the mother plant to each of its offspring (Westoby et al., 1992). Results obtained in the present study demonstrate that large seeds could allow seedling to survive for longer days after emergence. On the other hand, small size offer short period of persistence from emergence, which is in agreement with the results obtained by Westoby et al. (1992). The present study also indicates that it is not likely to relate the seed size to the seed mass. In other words, large seeds are not always heavy and small seeds are not necessarily light (e.g. Rununculus and Carduus). Results of several comprehensive studies (e.g. Schimpf, 1977; Sorenson & Miles, 1978; Stronberg & Patten, 1990) have suggested that plants in xeric habitats tend to have larger seeds, and consequently larger seeds might provide an advantage for seedling establishing in dry conditions. However, this study showed that xeric habitats tend to have smaller seeds. The advantage of large seeds in the arid and semi-arid habitats may be due to the fact that large seeds disperse over smaller distance and may attract herbivores (Westoby & Leishman, 1994). A seed may be large because it encloses an embryo (and endosperm) which have genotypes that are able to attract a greater than average supply of nutrient resources (Mogie et al., 1990). However, the number of seeds and their size in the present study seem to be largely determined by the ecology of the species. It is evident that very few species could tolerate more than 2% of NaCl solution (Chapman, 1966). This con- ecologia mediterranea, tome 29, fascicule 2, 2003
Page 1 and 2: Tome 29 Fascicule 2, 2003 ISSN 0153
Page 3 and 4: Rédacteur en chef Managing editor
Page 5 and 6: Vegetation along an elevation gradi
Page 7 and 8: V-shaped. The depth of valley reach
Page 9 and 10: Habitat type C (%) P (%) Second dom
Page 11 and 12: ecologia mediterranea, tome 29, fas
Page 13 and 14: Al-Jabal Al-Akhdar could be conside
Page 19 and 20: 140 ◆ M. A. SHEIKH, M. E. MADY &
Page 32 and 33: Interpreting germination results ba
Page 34 and 35: INTRODUCTION ecologia mediterranea,
Page 36 and 37: Habitat Species Family Canal banks
Page 38 and 39: Treatment Species H 2SO 4 Refrigera
Page 44 and 45: Potentiel hydrique et phénologie d
Page 46 and 47: INTRODUCTION ecologia mediterranea,
Page 54 and 55: POTENTIEL HYDRIQUE ET PHÉNOLOGIE D
Page 58 and 59: Phenotypic and phenological behavio
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Figure 3. Dendrogramme établi à p
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DIVERSITÉ GÉNÉTIQUE DE POPULATIO
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DIVERSITÉ GÉNÉTIQUE DE POPULATIO
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218 ◆ M. BARBERO INTRODUCTION Une
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220 ◆ M. BARBERO frutescens, Pote
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222 ◆ M. BARBERO loppé avec, dan
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224 ◆ M. BARBERO La dégradation
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226 ◆ M. BARBERO ticum, Hepatica
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228 ◆ M. BARBERO — une unité p
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230 ◆ M. BARBERO tes crêtes de l
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232 ◆ M. BARBERO loppées sur tou
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234 ◆ M. BARBERO — constitution
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236 ◆ M. BARBERO Etage méso-méd
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238 ◆ M. BARBERO L’étage monta
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240 ◆ M. BARBERO Bibliographie Ce
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242 ◆ M. BARBERO CAILLIAU A., 200
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244 ◆ M. BARBERO terranéen dans
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246 ◆ M. BARBERO répartition de
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250 ◆ FAITS DE CONSERVATION EN M
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262 ◆ ANALYSES D’OUVRAGES paysa
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264 ◆ ANALYSES D’OUVRAGES tradi
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