| Purslane (Portulaca oleracea L.), is widespread and has been ranked in the eighth most common plants in the world. It has gained more and more attention in recent years due to its high tolerance to multiple adverse conditions, excellent inhibition effects on harmful bacterias and abundant nourishments such as ω-3-fatty acids, flavonoid, K and so on. These advantages make it a promising candidate to form edible landscape and saline agriculture. Current studies on purslane are mainly about physiological and biochemical compositions and mechanisms.Purslane has two main types in our country, wild and cultivar type. However, almost there is no investigation on the classificatory relationship, characteristics of seed germination, specific tolerance to stress and differences on nutrient content. Hence, taking the seeds of the two microspecies of purslane, one is a commercial cultivar bought from Jingyan company, another is a wild type collected from the botanical garden in Nanjing Normal University, as our experimental metiarals. At the beginning, based on the research of the seed morphological characteristics, we analysed the classification and germination pattern of two purslanes. Then, we searched out the best conditons of seed gemination and seedling growth on account of features of seed dormancy and seed germination. At last, we detected the sensitive difference to drought, salty, akali, and salt-akali stress at the periods of seed geminated and seedling emergency of two purslanes, and tried to screen high resistant purslane with a severe NaCl treatment.1. Classification and germernation patterns of wild purslane and cultivar purslane seeds(1) The thousand-grain weight of wild purslane seeds (0.0795g±0.002) was significantly lower than that of cultivar purslane seeds (0.4775g±0.0009) and the size of wild purslane seeds (length:0.68cm±0.05, width:0.61mm±0.05) was significantly lower than that of cultivar purslane seeds (length:1.24cm±0.07, width:1.15cm±0.07) as well.These results showed that:seeds of two microspecies of purslane belonged to tiny seeds, so that either of them could form their own seed bank underground more easily than the big ones. It is very impotant to protect their population from environmental stress and to save the species and biodiversity. And there were greater differences on characteristics on seed coat morphology of wild and culitivar purslane. Ornamentation of seeds surface was more regular of wild purslane with rare tubercles, while tubercles were densely scattered on cultivar seeds. In addition, accorddding to above seed morphologic features, we verified the wild type into Portulaca granulatostellulata (Poelln.) C. Ricceri et P.V. Arrigoni which is hexaploid with54chromosomes, and the cultivar into Portulaca edulis Danin&Bagella which is tetraploid with36chromosomes.(2) Seed germinated pattern of.P. granulatostellulata and P. edulis was slow and rapid respectively:the former germinated need1day after being sought, germination last7-9days, and finally germination rate only40%around; the latter could germinated after being sought about6hours,1-2days completed its germination, and the germination rate would reached95%.Big seed size, papilla, fast water absorption and rapid germination made P. edulis show more potential of agricutrural cultivation in consideration of its rapid eatablishment. While the P. granulatostellulata may have capacities of forming seed bank, getting out of catastrophic adversity and concervating germplasm by small size, smooth testa and slow germination, so it may be suitable for ecological rehabilitation.2. The germination characteristics of P. granulatostellulata (wild type) and P. edulis (cultivar)(1) The P. granulatostellulata seeds harvest from wild fields had a dormancy period as long as6-8months and then dispeared with continuing storage. While the wild purslane seeds harvest from plant growth chamber where there had a superior living conditions was not going dormancy. If the P. edulis seeds had domancy characteristics, need a further investigation via harvesting seeds from field palnting.To break the dormancy of P. granulatostellulata seeds, the best seed soaking condition was12h,35℃.(2) During seed germinating period, the P. granulatostellulata seeds need light while the P. edulis not; the results of experiment of sowing depths on the germination of purslane seeds indicated that2mm sowing depth inhibited the germination rate of P.granulatostellulata seeds to21%, also the seed germination rate of the P. edulis decreased to80%.(3) For seedling forming of P. granulatostellulata and P. edulis seeds, both of them need suitbale temperatrue and light:P. granulatostellulata was sensitive to low temperature, preferred a higher temperature (32℃/28℃) and longer illuminaton; P. edulis seeds could germinate at the temperature of22℃/18℃,32℃/28℃and35℃/32℃), but germinated better at higer temperature. In addition, full light illumination was unsuitable to P. edulis seedling growth.3. Drought resistance and salt-alkali tolerance of P. granulatostellulata and P. edulis at their seed germinating stageResults indicated that:both seeds f P. granulatostellulata and P. edulis could germinated well in conditions of no lackage of water or mild water stress (PEG≤10%) or salt stress (NaC1＞100mM). Germination of wild seeds was promoted when exposured to light drought or light NaCl salt stress, the same results were not found in cultivar seeds. While, both seed germination were suppressed under moderate and high drought stress (PEG>10%) or moderate and severe salt stress (NaC1＞100mM) conditions, and the suppression of cultivated seeds was significantly (P<0.01) slighter than those of wild seeds. To seed germination of wild seeds, the optimum pH is a little acid, while for cultivar seeds,6.0-6.5is the most suitbale pH. High pH was unfavourable to both of them. Both seeds could germinate well but could not establish seedling under the alkali stress with Na2CO3≥25mM. Hence, we suggested that P. granulatostellulata and P. edulis could be developed in the regions with a light drought stress and mild salt or alkali fields, and the latter also could be developed in the areas with moderate or severe drought stress and saline lands. |
PDF Full Text Request