| Survival and reproduction are the main means of maintaining and sustaining populations.Moisture is an important limiting factor for plant growth and reproduction in arid and semi-arid areas.Therefore,plants will adapt to the changes of water in the environment through a series of strategic adjustments(morphology,physiology,phenology,biomass allocation,reproduction).Helianthus tuberosus L.is a drought-tolerant plant planted in the area that has asexually propagate(tuber reproduction)and sexually propagate(seed reproduction).In this paper,high-line(LZJ040,high seed setting rate)and low-line(LZJ004,low seed setting rate)Helianthus tuberosus L.were selected as test materials.Six water gradients were set up(0?600?1200?1800?2400?3000 m~3/hm~2).The morphology,net photosynthetic rate,flowering,biomass allocation,reproductive output and other indicators were measured to explored the changes in the survival and reproductive strategies of the two lines along with water,and to explain the mechanism of improving the fitness.The results showed that the survival and reproduction strategies of two lines along the water gradients were as follows:(1)The net photosynthetic rates of the high-and low-line Helianthus tuberosus L.showed an increasing trend in nutritional growth and the flowering stage,and nutritional growth stage was significantly higher than the flowering stage.The plant height,stem diameter and leaf area all showed an increasing trend.(2)The biomass allocation of high-and low-line Helianthus tuberosus L.changed significantly.At the flowering stage,the root-shoot ratio of two lines decreased first and then increased(less than 1).At the maturity,the root-shoot ratio of two lines showed a decreased trend(overall 1).From flowering to maturity,biomass allocation was transferred from the aboveground to the underground part and the stem was reduced the most.(3)The dry weight of tubers and the number of tuber buds of high-and low-line Helianthus tuberosus L.had an increasing trend,indicating that water promoted the asexual reproduction of two lines.Under the different treatments,dry weight of tubers of low-line which was not significant,but high-line was significant.The results showed that the effect of water on asexual reproduction of high line was greater.There is a trade-off between the number of tubers and the average dry weight of tubers.(4)The dry weight and the number of flowers,the number and dry weight of seeds of high-and low-line Helianthus tuberosus L.all showed an increasing trend.The water could significantly promote the sexual reproduction of two strains.There is a trade-off between the number of seeds and the average dry weight of seeds.(5)The proportion of seeds increased and tubers decreased,there was no significant correlation between them,indicating that there was no trade-off between the two reproductive modes.Both TD/SD and TN/SN showed a decreasing trend.Compared with asexual reproduction,the influence of water on sexual reproduction was higher.From the above:water has a significant effect on survival and reproduction strategies of high-and low-lines of Helianthus tuberosus L..It will adapt to the changeable environment and improve fitness through the change of survival and reproduction strategies.The accumulated resources of Helianthus tuberosus L.are mainly stored in vegetative organs before propagation.With the formation of tubers,the stored resources are transferred from vegetative organs to reproductive organs and there is a trade-off between of them.At the same time,with the increase of water and the improvement of environmental conditions,both species of Helianthus tuberosus L.tend to sexual reproduction.The genetic diversity and fitness are increased through the adjustment of reproduction mode. |
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