| Potassium is one of the macronutrients essential for plant growth and development. The potassium requirement of plants is very high for plant growth and production. Recently, with the yield and quality of agricultural products increasing, crops nedds more potassium nutrient to meet its requirement. However, most potassium (98%) in soil is a mineral state and slowly available form, which plants not directly absorb, and led to potassium deficiency. Furthermore, our country is severe shortage of potassium resources, and the potash consumption in our country was mainly depended on import. So it has important theoretical and practical significance to explore plants own potential for improving soil potassium and fertilizer potassium use efficiency by screen K-efficient and low-K tolerant genotypes.The paper used16different sources materials of Houttuynia Thunb., carried out preliminary screening K-efficient genotypes on tested materials by soil and solution culture. On the basic of it, the paper discussed the mechanism of different types of Houttuynia Thunb materials adapt to low potassium solution culture, studied plant production, photosynthesis, antioxidant ability, chemical constitution and contents of.volatile oil, root morphological and physiological characteristics as well as components of root exudates, revealed the mechanism of potassium nutrition efficiency differences of different potassium efficiency genotypes, provided a theoretical basis for further development and utilization of Houttuynia Thunb. The potassium efficiency of WO1-32-1was in middle level. The study also tried to explore the characteristics of photosynthesis and secondary metabolites under different supplied potassium concentrations. Houttuynia cordata Thunb. W01-100is planted as a new line for disease resistance and high-quality and yield. Therefore, the paper also researched about the interactive effects of salinity and potassium on growth, water content, chlorophyll content, ionsand organic accumulations as well as oxidative enzymes activities on WO1-100.1. Under low potassium solution and soil cultures, the16different materials has been carried out low-potassium soil culture and solution culture experiment. And then K-efficient and K-inefficient genotypes were selected by plant potassium contents, potassium uptakes and utilization ratios, and root morphology characters. The contents of potassium in plant were higher than9.0%and5.50%and the utilization ratio of potassium were higher than2.50%,0.30%, respectively, and the uptake ratio of potassium in per plant were more than1.5μmol·(g·h)-1, so the genotypes W01-34and W01-86were the genotype of enrichment in potassium. However, the genotypes W01-4and W01-99had lower contents of potassium lower than8.5%and5.0%, and the utilization ratio of potassium were lower than2.00%、0.30%, respectively, under solution and soil cultured with low potassium. Besides, the uptake ratio of potassium in per plant were less than0.65μmol·(g·h)-1. The two genotypes were the genotypes with low potassium.2. The plant photosynthesis, antioxidant ability, and root morphology and physiological characteristics as well as secondary metabolites of the K-efficient (W01-86, W01-34, W01-71) and K-inefficient (W01-4, W01-99) genotypes had been researched with low potassium and normal potassium conditions by solution culture. The results showed that K-efficient genotypes had significant higher K contents in shoot and rootstock in comparison with K-inefficient genotypes, regardless of potassium levels. K-efficient genotypes had significant higher fresh shoot weight compared to K-inefficient genotypes, but the latter had higher ratio of root/shoot. Secondly, chlorophyll content showed no difference. However, the photosynthetic rate and intercellular CO2concentration of K-efficient genotypes were obvious higher than K-inefficient genotypes. The photosynthetic rate of the former was2times as the latter. And decreased potassium levels significantly declined photosynthetic rate and intercellular CO2concentration for both genotypes. Third, in general, K-efficient genotypes had higher antioxidant enzymes activities in comparison with K-inefficient genotypes. Low supplied potassium level dramatically decreased leaf and root SOD, POD and CAT activities, but except for W01-71. Fourth, potassium levels played no significant difference on root active and total uptake areas and volume. H+excretion content of K-inefficient genotypes was1.5～2times as K-efficient, but the latter root activity was1.6-2.5times as that of the former. Fifth, potassium concentrations and genotypes played no significant difference on root exudation pH. However, we found that the mean soluble sugar, protein content, total amino, oxalic acid, phenol content in root exudates for K-efficient genotypes were significant higher than K-inefficient genotypes, and these components were positively correlated with supplied potassium levels. Especially, the oxalic acid in K-efficient genotypes was8.9～25.8times as that in K-inefficient genotypes. Sixth, the volatile oils were analyzed by GC/MS led to the identification of55components, and11components were characterized in all the studied plants. And more total momoterpenes contents were observed in K-efficient genotypes accompanied with K-efficient genotypes. However, K supply played no significant difference in total monoterpene contents for each genotype.3. By tissue culture with4potassium concentrations on Houttuynia cordata Thunb. W01-32-1-1was carried out. The study showed that K-starvation and low-K treatments significantly induced roots develop increased plant yield. Chlorophyll contents and transpiration rate of W01-32-1were negatively correlated with supplied potassium levels, but intercellular CO2concentration increased with rising potassium levels, while plants in low-K treatment had the maximum value of photosynthetic rate. Increasing supplemental potassium levels significantly increased shoot and root K+contents, decreased Na+contents, but shoot and root Mg2+, Ca2+showed different trends. Moreover, the study found that K-starvation condition could induce the flavonoids synthesis in W01-32-1, its content was1.5times of that in the highest potassium treatment. However, no significant difference was found on quercetin content. In total, potassium levels of treatments from low to high were indentified32,17,22and11components in volatile oil by GC/MS, respectively. Only4monoterpenes in all the materials, and showed no significant differences on potassium levels. All these led to that W01-32-1-1tended to adapt to K+-deficiency and low-K+conditions, compared to high-K+conditions.4. Houttuynia cordata Thunb. W01-100was desirable traits like disease resistance, high-quality and yield. The aim was to study Houttuynia cordata Thunb. W01-100growth and characteristics of nutrient elements absorption, antioxidant enzymes (CAT, SOD, POD) activities and other physiological indicators. The results showed that high Na+dramatically decreased W01-100growth and root development. However, low Na+induced root development. K+could dramatically inhibit Na+absorption, and to a certain extant, Na+could replace K+nutrition. CAT and POD activities were gradually increased with increasing Na+concentration. By contrary, SOD activity was negatively associated with Na+. Supplemental K+significantly rise CAT and SOD activities, but its increased extent was lower than that resulted of increasing Na+concentration. The free proline and soluble sugar contents in leaves showed an increasing trend with increasing salinity, and accumulation of it played important roles in osmoregulation and antioxidant enzymes activities. All these indicated that K+fertilization could compensate partly for the negative impact of salinity. |
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