Drought-induced Transgenerational Plasticity At The Germination And Seeding Stages In Caragana Korshinskii Kom

Transgenerational plasticity occurs when the environment experienced by parents affects the phenotypes of their offspring,which may increase or decrease the adaptability of their offspring.Due to the impacts of future climate change and human activities,drought will increase in frequency and intensity.Adaptive transgenerational plasticity may be very important for plants to adapt to drought because plants are sessile.Caragana korshinskii Kom.is a perennial shrub with strong drought-resistance.It is unclear whether drought-induced transgenerational plasticity occurred at its germination and seeding stages.Therefore,Data integration analysis,germination and pot experiment were used to study:1)the effects of precipitation,life form,seed mass on hydrotime model parameters,2)the difference of hydrotime model parameters during germination in different seed sources along precipitation gradient,3)the intensity of drought-induced transgenerational plasticity at seedling stage along precipitation gradient,respectively aimed to demonatrate the adapative mechanism of this species to long-term drought and provide references for its rational introduction and cultivation.The main results are as follows:（1）Data integration analysis showed that precipitation did not affect the hydrotime parameters of germination,but life form and seed mass had some effects on the hydrotime model parameters of seed germination.Water potential thresholdψ_b（50）for germination of annual plants（-1.06±0.09 MPa）was significantly lower than that of perennial plants（-0.84±0.10 MPa）.Theψ_b（50）values of grains vegetables and fruits were lower than those of weeds and other plants.Domestication reduced the water potential threshold of germination.Seed mass was negatively correlated withψ_b（50）.The hydrotime parameters of herbaceous plants had no correlation with seed mass,but the seed mass of woody plants was negatively correlated withψ_b（50）,and positively correlated with hydrotime constantθ_H.There was also a negative correlation betweenψ_b（50）andθ_Hof woody plants.This indicates that large-seed woody plants adapt a drought resistant germination strategy,which is conducive to the rapid growth and survival in arid habitats.（2）The germination test showed that the influence of germination temperature on hydrotime model parameters was larger than that of seed source.The seed source had a significant or marginally significant effect on theθ_H andψ_b（50）,but seed sources in relatively arid regions did not induce adaptive transgenerational plasticity.Theθ_H of Ansai was significantly lower than that of the other three sites,and theψ_b（50）of Ansai and Shenmu was significally lower than that of Gonghe.Theψ_b（50）at optimal germination temperature（25℃）was the lowest.Theψ_b（50）of different seed sources was mainly affected by the annual mean temperature.Seed sources with high annual mean temperature had lowerψ_b（50）value.（3）Pot experiments showed that drought-induced transgenerational plasticity occurred in seedlings of Caragana korshinskii from different seed sources,but the direction and intensity of transgenerational plasticity was depended on the plant traits.Parental drought significantly improved the water status and photosynthesis of the offspring during drought.With the increase of drought duration,the transgenerational plasticity of Caragana korshinskii was enhanced,suggested by more improved physiological growth indexes after drought.This adaptation may contribute to enhance the acclimation of Caragana korshinskii to long-term drought.However,the transgenerational plasticity of Caragana korshinskii was not linearly related to the intensity of parental drought signals.Liangcheng with medium drought signal had stronger adaptability and transgenerational plasticity than Gonghe.In summary,this study showed that adaptive transgenerational plasticity didn’t exist during seed germination of Caragana korshinskii,plant water status and photosynthetic gas exchange exhibited certain adaptive transgenerational plasticity,but that didn’t confer to the advantage of growth.