| Spring ephemeroides are perennial underground bud plants, which grow in broadleaved deciduous forest and theropencedrymion in North Temperate. They are important components of understory herb layers and biodiversity, with a life-history characteristic of rapid flowering and fruiting when snow melt in early spring, then withering and dying after canopy closing, finally getting into dormancy stage. There are lots of reports about community characteristics and flora distribution of spring ephemeroides plants, but few on growth regulation of population modules and underground characteristics during aestivation period. Four spring ephemeroides plants(Adonis amurensis; Gymnospermium microrrhynchum; Corydalis fumariifolia; Erythronium japonicum) were selected as objects,which were grown in Changbai Mountain, China. We conducted a systematic study on growth and allocation features of population modules during growing season, morphological characteristics and growth rhythm of underground buds in summer dormancy, physiological characteristics of different growth stages. A series of results were obtained about growth strategies of spring ephemeroide populations and growth laws of underground modules in summer dormancy. The study provides a reference for further study on the mechanism of convergence adaptation of spring ephemeroide plants. The main results and conclusions are as follows:(1) The phenotypic plasticity of modules growth were accordant in four spring ephemeroide populations. The phenotypic plasticity of biomass was higher than that of plant height. There was a significant(P<0.05) or extremely significant(P<0.01) positive linear correlation between biomass of reproductive and storage components and total plant or aboveground part biomass, and it was positive power function or exponential function in some growth period. The largest proportions of biomass were used for store in whole growing season. They were 63.41% ~ 68.71%, 73.72% ~ 84.88%, 38.87% ~ 54.24%,48.57%~64.87%, respectively, for A. amurensis, G. microrrhynchum, C. fumariifolia and E.japonicum. But least proportions for sexual reproduction, 2.61%~6.28%, 3.22%~8.36%,12.37% ~ 20.58%, 3.04% ~ 8.41%, respectively. The relative growth rate and seasonal biomass distribution dynamics were highly consistent on modules of G. microrrhynchum,C.fumariifolia and E. japonicum populations. The populations of A. amurensis had relatively different regularity. Plasticity variation of biomass distribution used for store module was smaller, but it was larger for reproduction during growth period. The biomass accumulation in storage organs used for next season generally began initial after fruiting or blooming fruiting but before fruit developing rapidly.(2) Differentiation processes of underground buds were asynchronous among the four spring ephemeroides. Rhizomes of A. amurensis began to differentiate new roots and buds at blooming flowering period in mid-April. Differentiation processes of underground buds included bud scale differentiation stage, initial stage of floral differentiation, sepal differentiation stage, petal differentiation stage, stamen differentiation stage and pistil differentiation stage. The whole differentiation underwent three months or so. Bulbs of E.japonicum began to differentiate new buds in mid-to-late May when terminal period, and the differentiation was divided into five phases: leaf differentiation stage, initial stage of floral differentiation, perianth differentiation stage, stamen differentiation stage and pistil differentiation stage. The differentiation would last for one and a half months. Tubers switched to dormancy for two months after plants of G. microrrhynchum and C. fumariifolia died, and buds differentiation began in late July. The differentiation included sprouted phase,initial stage of inflorescence differentiation, inflorescence formative and floral organ differentiation stage. These phases would take two months. When underground buds of four spring ephemeroides finished their morphogenesis, got into underground growth phase immediately and formed mature buds and inflorescences before soil freezing, then went into dormancy.(3) It has a consistent regularity on the growth of underground buds of spring ephemeroides. The relationship between bud length and diameter was extremely significant allometric growth of power function(P<0.01). Growth rate of bud length was faster than that of bud diameter in growth stage of underground. The growth rate was asynchronous in different development stages, and allometric growth rhythm with priority elongation or increase. Bud growth also showed allometric growth law that preferential elongation then thickening the radial. The summer dormancy of spring ephemeroides was advantageous with growth transfer to underground, so that to escape competition for light resources, but not to defense stress injury.(4) The dynamic change of contents on soluble sugar, reducing sugar and starch were coincident in aboveground parts of four spring ephemeroides, and the contents were lower at the early flowering stage, then increased gradually and maintained a high level at fruiting stage. The contents of soluble protein, MDA and activity of SOD, POD in storage organs maintained higher in underground parts at early flowering stage. It was a kind of physiological defense responses to low temperature. A. amurensis and G. microrrhynchum had relatively uniform law on dynamics of carbohydrate, soluble protein and MDA content,also the activity of protective enzymes. Different with the former, the change of E. japonicum was similar to C. fumariifolia.(5) During morphological differentiation of underground buds in four spring ephemeroides, the contents of soluble sugar, sucrose and soluble protein, the activity of protective enzymes maintained a high level, but the contents of glucose, fructose, reducing sugar and starch maintained a low level. At the early development of underground bud, the contents of soluble sugar, sucrose and soluble protein, as well as activity of SOD and POD,all kept in low levels. The contents and activities increased gradually with the decrease of temperature at the later period. It showed a regularly variation of physiological characteristics of underground storage organs in four spring ephemeroides plants. |
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