【摘要】：沉水植物是淡水生態(tài)系統(tǒng)中重要的初級(jí)生產(chǎn)者,參與了淡水生態(tài)系統(tǒng)中氮、磷營養(yǎng)鹽的循環(huán)過程,通過恢復(fù)沉水植物是修復(fù)富營養(yǎng)化水體的一種常用方法,因此研究沉水植物吸收氮、磷營養(yǎng)鹽的過程具有重要意義。本文選擇典型的沉水植物—菹草為研究對(duì)象,通過開展一系列室內(nèi)模擬實(shí)驗(yàn),考察了菹草莖葉(斷枝)對(duì)營養(yǎng)鹽的吸收效果;探討了富營養(yǎng)條件下菹草吸收營養(yǎng)鹽的途徑;比較了貧富營養(yǎng)條件對(duì)菹草吸收和利用營養(yǎng)鹽途徑的影響。主要結(jié)果如下:(1)菹草莖葉(斷枝)在富營養(yǎng)水體中,其斷枝的莖長和鮮重有顯著增長(p0.05),菹草莖葉(斷枝)蓋度為50%和100%的處理組中的平均單株石芽數(shù)為2.09和2.67個(gè)。在試驗(yàn)條件下,隨著菹草莖葉(斷枝)蓋度的增加,水體中氮磷營養(yǎng)鹽的衰減速率越快。第3 d時(shí)蓋度為50%和100%的處理組中TN和TP均顯著下降(p0.01),當(dāng)水體中NH_4~+-N大于0.35 mg·L-1時(shí),菹草優(yōu)先吸收NH_4~+-N再吸收NO3--N。此外,水體中的浮游和底棲藻類明顯下降,系統(tǒng)中浮游優(yōu)勢藻由綠藻屬的鼓藻和小球藻逐漸變成微囊藻和綠藻,而底棲藻類表現(xiàn)出藍(lán)藻門的藻類逐漸增多的趨勢,而不再以綠藻藻類為主要藻類的群落結(jié)構(gòu)。(2)在試驗(yàn)條件下,沉積物包被組中水體中的氮磷營養(yǎng)鹽消減的最快,在第18 d時(shí)水體中的TN和TP較起始時(shí)的消減率分別為62.58%、90.07%,其他4組TN的衰減率均小于60%;沉積物中的無機(jī)氮主要氮形態(tài)為NH_4~+-N,其中沉積物裸露的處理組沉積物中NH_4~+-N和TP的消減率要高于沉積物包被組,沉積物包被組中NH_4~+-N和TP較起始時(shí)的消減率分別為39.05%、10.95%,表明沉積物中的營養(yǎng)鹽存在部分向水體中釋放的過程。因此,菹草在富營養(yǎng)化水體中根系可以吸收沉積物中的氮磷營養(yǎng)鹽,同時(shí)沉積物中的氮磷營養(yǎng)鹽可以向水體中釋放供菹草莖葉吸收。(3)在貧富營養(yǎng)條件下,菹草最大莖長、單株平均株重、RGR以及菹草葉片的光合作用速率差異不大。實(shí)驗(yàn)開始后,貧富營養(yǎng)條件菹草的氮磷含量逐漸升高,第42 d和60 d時(shí)PTN和PTP分別達(dá)到極大值,兩者差異不顯著(p0.05)。在富營養(yǎng)條件下水體中的氮磷營養(yǎng)鹽和菹草的PTN和PTP之間呈顯著負(fù)相關(guān)(p0.05),而在貧營養(yǎng)條件下,菹草體的氮磷和水體中的氮磷無直接關(guān)系。第30 d時(shí)富營養(yǎng)組中水體TN消減達(dá)到73.57%,第18 d時(shí)富營養(yǎng)鹽組TP消減達(dá)到87.50%,對(duì)照組中TP消減率為51.02%,但對(duì)照組中水體TN有小幅度上升。菹草在貧富營養(yǎng)條件下吸收營養(yǎng)鹽的途徑不同,在富營養(yǎng)條件下,菹草可以利用根系和莖葉共同吸收營養(yǎng)鹽,但是在貧營養(yǎng)條件下,菹草只能利用根系吸收水體中的營養(yǎng)鹽。所以營養(yǎng)狀態(tài)的改變可以改變菹草吸收營養(yǎng)鹽的方式。
[Abstract]:Submerged plants are important primary producers in freshwater ecosystems and participate in the cycle of nitrogen and phosphorus nutrients in freshwater ecosystems. Restoring submerged plants is a common method to repair eutrophication water bodies. Therefore, it is of great significance to study the process of absorbing nitrogen and phosphorus nutrients by submerged plants. In this paper, crispus, a typical submerged plant, was selected as the research object, and a series of laboratory simulation experiments were carried out to investigate the effect of stem and leaf (branch breaking) on the absorption of nutrients, and the ways of absorbing nutrients by crispus under eutrophication conditions were discussed. The effects of rich and poor nutritional conditions on the absorption and utilization of nutrients by Potamogaster crispus were compared. The main results were as follows: (1) the stem length and fresh weight of crispus were significantly increased in eutrophication water (p0.05). The average number of stone buds per plant in 50% and 100% treatment groups was 2.09 and 2.67, respectively. Under the experimental conditions, the faster the decay rate of nitrogen and phosphorus nutrients in water was with the increase of stem and leaf coverage (branch breaking) of Potamogaster crispus. On the 3rd day, TN and TP decreased significantly in the treatment group with coverage of 50% and 100% (p0.01). When NH_4~-N in water was greater than 0.35 mg 路L-1, crispus preferred to absorb NH_4~-N and reabsorb NO3--N.. In addition, the algae in the water body decreased significantly, and the dominant algae in the system gradually changed from chlorella and Chlorella to microcystis and green algae, while benthos algae showed a trend of increasing algae in the phylum cyanophyta. The community structure of green algae was no longer the main algae. (2) under the experimental conditions, the nitrogen and phosphorus nutrients in the water body of the sediment coating group decreased the fastest. On the 18th day, the attenuation rates of TN and TP in water were 62.58% and 90.07%, respectively, and the attenuation rates of TN in the other four groups were less than 60%. The main nitrogen form of inorganic nitrogen in sediment is NH_4~-N, in which the reduction rate of NH_4~-N and TP in sediment exposed treatment group is higher than that in sediment coating group. The decreasing rates of NH_4~-N and TP in sediment coating group were 39.05% and 10.95%, respectively, indicating that part of the nutrients in sediments were released into water. Therefore, the roots of crispus can absorb nitrogen and phosphorus nutrients in sediments, and the nitrogen and phosphorus nutrients in sediments can be released into the water for absorption. (3) under the condition of rich and poor nutrition, the maximum stem length of crispus can be obtained. There were no differences in photosynthesis rate among average plant weight, RGR and P. crispus leaves. After the experiment, the content of nitrogen and phosphorus increased gradually in rich and poor nutritional conditions, and the PTN and PTP reached the maximum on the 42nd and 60th day, respectively, and there was no significant difference between the two groups (p0.05). There was a significant negative correlation between nitrogen and phosphorus nutrients in water and PTN and PTP in Potamogaster crispus under eutrophication condition (p0.05), but there was no direct relationship between nitrogen and phosphorus in Potamogaster crispus under the condition of poor nutrition. On the 30th day, the TN of eutrophication group decreased by 73.57%, the TP of eutrophication group decreased 87.50% on the 18th day, and the TP reduction rate of control group was 51.02%, but the TN of water body increased slightly in the control group. Crispus can absorb nutrients by roots and stems and leaves under the condition of rich and poor nutrition, but under the condition of poor nutrition, crispus can only use roots to absorb nutrients in water. Therefore, the change of nutritional status can change the way Potamogpus crispus absorbs nutrients.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：X52;X173

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