Ecological Adaptability Of Bromus Inermis Under Temperature And Water Changes

The increased frequency of climate extremes around the world has made the environment for genetic resources and biodiversity of biological species more critical.Temperature and precipitation are important ecological environmental factors that play a vital role in plant growth,and plant adaptation to their changes is important for predicting future trends in the context of changing climate.As an important wild forage germplasm resource in Xinjiang,the adaptive performance of the growth and reproduction of Bromus inermis under temperature and moisture changes provides a theoretical basis for exploring the adaptive responses of wild forage grasses to climate change.In this paper,Bromus inermis was used as the research object,and three warming treatments(CK,W1,W2)and six precipitation treatments(W-F3,W-F6,WF3,WF6,W+F3,W+F6)were simulated using the open-top warming chamber in the field,and five temperature treatments(T1,T2,T3,T4,T5)and five moisture treatment experiments(W-70%,W-30%,W,W+30%,W+70%)were set up in the indoor control.The adaptation to temperature and water changes during the germination,seedling and reproduction stages was studied,the growth characteristics of different stages,anatomical structure,physiological characteristics and transcriptome of leaves and roots at the seedling stage were determined,and the methods of principal component analysis,cluster analysis and through path analysis were used for comprehensive evaluation.To analyze the specific ways in which temperature and moisture affect each growth stage of Bromus inermis,to investigate the relationship between external morphology and internal regulation of the plant,to clarify its adaptive responses to temperature and moisture changes.The results of the study can enrich the adaptive mechanism of Bromus inermis in response to the changes of hydrothermal environment,and provide theoretical basis for the conservation and exploitation of Bromus inermis germplasm resources.The main results are as follows.(1)The seed germination stage responded more significantly to temperature changes compared to other growth stages,and the field simulated W2 temperature increase treatment increased the seedling emergence rate by 1.49 times;in the controlled indoor temperature from 15/5℃ to 25/15℃,the seed germination rate was 1.12 times higher at 25/15℃ than at 15/5℃.With the increase of temperature,the above-ground part was more sensitive to the increase of temperature than the underground part,and the growth ability of the seedlings was stronger.The growth of vegetative organs,such as leaves and stems,was improved by simulating W1 in the field,and the growth of reproductive organs was improved by W2.The frequency of precipitation had no significant effect on seed germination and seedling growth(P >0.05).The seedling emergence rate increased by 10.60% with the increase of total precipitation,and the root growth increased by 27.80% with the decrease of 70% of precipitation,the allocation of vegetative growth resources increased by 9.00% under W+F6 increasing water treatment.(2)The leaf thickness and root diameter of Bromus inermis decreased by 75.76% and 75.60%.Cell thickness,vascular bundle area,vessel diameter and cortex thickness decreased firstly and then increased,and enzyme activity in leaves decreased by 95.59%.Compared with low temperature,T1 treatment could accumulate more malondialdehyde,free proline,soluble protein and soluble sugar.Increasing water by70% promoted the expansion of leaf microstructure,increased the thickness of upper epidermis by 39.7%,increased the length of root microstructure by at least 30.6%,and decreased the contents of MDA and soluble protein by 43.72% and 61.63%,respectively,the soluble sugar content increased 1.2 times and the enzyme activity decreased 20.64% on average,the activity of Catalase in roots decreased by 17.00%.Water reduction of 70% decreased root diameter by 21.2%,increased cortex thickness by 26.4%,increased MDA,free proline and soluble sugar by 79.8%,44.79% and 1.41 times respectively,and decreased soluble protein by 17.98%,catalase and Peroxidase activities complement each other.(3)Transcriptome sequencing of 36 samples sequenced under temperature and moisture treatments resulted in a total of 275,606 Unigenes,annotated into 7 major functional databases(Nr,NS,KO,Swissprot,Pfam,GO,COG/KOG).Decreasing temperature screened more differentially expressed genes(DEGs)from the root system and involved in metabolic pathways;increasing temperature obtained more DEGs from the leaves and involved in photosynthesis and material synthesis processes.The number of DEGs in the root system was much higher than that in the leaves in both the 70% water increase and 70%water reduction treatments.The 70% water increase treatment mobilized more DEGs in the leaves to participate in photosynthesis,while the root system was involved in the signaling pathway to stabilize seedling growth.(4)Increasing temperature decreases the chance of Bromus inermis seedling emergence,which relies mainly on increasing seedling leaf length to obtain more resources after emergence,and DEGs are involved in photosynthesis to increase leaf chlorophyll content and promote leaf growth.Increased temperature promotes the increase of plant height during the reproductive period and improves the input of nutrient organ resources to adapt to the increased temperature environment.The accumulation of root biomass was increased from seedling stage,and the length of root microstructure was decreased to increase the water absorption capacity.Increased water enhances leaf biomass accumulation and substantial water increase facilitates leaf microstructure expansion.Subsequently,the aboveground and underground biomass were increased,and the individual’s reproductive capacity was also enhanced significantly.Water reduction accelerated the emergence of seeds,increased root length and increased root biomass after rapid emergence,but inhibited the expansion of root microstructure,long-term water shortage inhibited the growth of individuals during the reproductive period,the plant still allocates more resources to the underground part,reduces the investment to the reproductive organ resources,guarantees the individual to obtain more water to sustain the growth.Overall,Bromus inermis seeds start germination after adapting to temperature and moisture changes,can actively mobilize internal substances as well as regulate differentially expressed genes to adapt to the environment during the fragile seedling stage,and will eventually choose to favor reproductive or nutritional growth to maintain population stability during the reproductive stage depending on changing environmental factors.