| Soil-mediated interactions between plants can occur through plant-soil feedback,where plants have different effects on later plants by changing the soil.Crops often adopt different growth strategies to cope with the nutrient differences caused by different soil phosphorus(P)levels.Long-term continuous cropping of tomato will lead to yield reduction,so establishing a reasonable crop rotation system can ensure soil fertility,promote the increase of tomato production,and is conducive to the sustainable development of tomato planting.In this thesis,through the pot experiment,we firstly set up 14 common crops(6 species genera)with different genetic distance and functional traits and two P application levels(40 and 200 mg kg-1),two-factor(crop species × P level)test treatment,to study the above-ground and the below-ground traits of different crops at high and low P levels in the greenhouse and the change of correlation strategies.Then,on the basis of experiment 1,a two-factor(crop species × P level)test treatment of 14 crops under continuous cropping and two P application levels(40 and 200 mg kg-1)was set up to explore the plant-soil feedback effect of different crops under continuous cropping in home soil.Finally,the effects of different genetic distance crops and P levels on tomato growth were studied by setting two kinds of tomato,14 kinds of rotation treatment and 3 factors(variety × P level × previous crop)test treatment of two P application levels(40 and 200 mg kg-1).The main results are as follows:1.Under low P level,crop biomass and P concentration decreased significantly,but leaf biomass ratio increased with a range of-16.10%to 27.57%.Root morphological traits,such as root length,fine root length and root surface area dreased,and the largest decreases were 88.60%(eggplant),88.58%(eggplant)and 38.58%(eggplant)for Solanaceae,respectlvely.The root shoot ratio decreased significantly(56.91%),while the specific root length increased significantly(-22.10%～142.50%).Low P level significantly increased mycorrhizal colonization rate of crops,and the highest mycorrhizal colonization rate was 75.80%(scallion),while available P content in rhizosphere soil significantly decreased,but the effects on rhizosphere acid phosphatase(A-Pase)activity and total organic acid content were not significant.At low P level,the correlation between crop root traits and soil available P content was enhanced.The relationship between root exudates,mycorrhizal colonization and root characters was enhanced at high P level.Low P supply significantly improved the direct and indirect effects of rhizosphere soil available P content,A-Pase activity,total organic acid content and mycorrhizal colonization rate on total biomass,enhanced the indirect effects of soil available P,but weakened the direct and indirect effects of mycorrhizal colonization rate.2.Crop biomass,P content and root traits significantly decreased under continuous cropping at two P levels.Among them,cucurbitaceae crops suffered the most serious continuous cropping obstacles,while gramineae crops suffered the least continuous cropping obstacles.Continuous cropping at low P level resulted in significant decrease in biomass of other crops except gramineous crops,decreased by 45.03%～95.31%(shoot biomass)and 37.94%～80.65%(root biomass).The root length and fine root length decreased significantly,while root surface area and root volume increased significantly.Mycorrhizal colonization rate and A-Pase activity were significantly increased(A-Pase activity increased 58.55%-491.54%).Low P supply aggravated continuous cropping obstacles,but with the increase of root diameter,the effects of continuous cropping obstacles dereased.3.At low P level,the biomass and P content of various organs of rotating tomato decreased significantly;wild-type tomato had better photosynthetic adjustment ability under rotation system,showed stability of photosynthetic index,and significantly increased chlorophyll content.Under the rotation system,the root changes of wild-type tomato were more significantly responsive to the low P level.At low P level,root morphological traits of wild-type tomato showed a strong improvement effect,especially in the direction of root length and root surface area(the ranges were-91.74%～329.07%and-84.70%～148.65%,respectively).At the same time,A-Pase activity changed strongly,but the mycorrhizal colonization rate of wild-type tomato varied less than that of the common tomato.4.At high P level,except for cucurbit,other rotation patterns could promote the growth of tomato.The genetic distance of previous crops ranged from 3.76×108 to 2.06×108 years,which had a significant growth promotion effect on tomato,among which,lettuce as the front crop had the most significant growth promotion effect.The previous crop rotation or continuous cropping of the same family with a genetic distance of 8.89×106 to 0 years inhibited the growth of tomato,and this kind of growth disorder was most obvious for the common tomato.At low P level,crop rotation and continuous cropping of the same family even caused the death of common tomato.In conclusion,root exudates,combined with root morphology and mycorrhizal symbiosis,jointly shape diversified P acquisition strategies,and there are a series of trade-offs between different root functional traits.Wild-type tomato is more resistant to stress and depends more on root morphological changes in low P soil.Continuous cropping inhibited the growth of crops,but with the increase of root diameter,the influence of continuous cropping was weakened.Wild-type tomato with rotation is more resistant to stress,more sensitive to changes in P environments,and more dependent on changes in root morphology.In the direction of genetic distance of 3.76×108 to 2.06×108 years,except for cucurbit,other crop rotation patterns could promote the growth of tomato,and the crops with closer genetic distance had more significant growth promotion effect on tomato.Crop rotation or continuous cropping in the same family is not conducive to tomato growth. |
PDF Full Text Request