• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Polyaspartic acid mediates the absorption and translocation of mineral elements in tomato seedlings under combined copper and cadmium stress

    2019-05-10 06:13:58HUMeimeiDOUQiaohuiCUlXiuminLOUYanhongZHUGEYuping
    Journal of Integrative Agriculture 2019年5期

    HU Mei-mei, DOU Qiao-hui, CUl Xiu-min, LOU Yan-hong, ZHUGE Yu-ping

    National Engineering Laboratory for Effcient Utilization of Soil and Fertilizer Resources/College of Resource and Environment, Shandong Agricultural University, Tai'an 271018, P.R.China

    Abstract Polyaspartic acid (PASP) is a nontoxic, biodegradable, environmentally friendly polymer and is widely used as a fertilizer synergist in agricultural production. In many old orchards and vegetable gardens, highly fertile soil is often accompanied by severe heavy metal contamination. The present study was designed to investigate mineral element interactions mediated by PASP under copper (Cu)+cadmium (Cd) combined stress to provide reasonable suggestions for scientif ic fertilization. A pot experiment was conducted in which tomato seedlings served as plant materials. A concentration of 700 mg L-1 PASP and foliar spraying application methods were selected based on previous experiments. Four treatments were applied: normal soil (control (CK)), Cu+Cd (combined stress), Cu+Cd+PASP, and normal soil+PASP. The plant biomass, root activity, and mineral elements were measured, and these data were analyzed by Data Processing System (DPS) statistical software. The results showed that, under Cu+Cd combined stress, PASP promoted stem diameter growth, root activity and chlorophyll content and ultimately increased the biomass of tomato seedlings to different degrees. Moreover, the content of both Cu and Cd and their individual accumulation in plants decreased. PASP increased the distribution of Cu and Cd in the roots under Cu+Cd combined stress, and the translocation ability from the roots to shoots was signif icantly restricted. With respect to essential elements, PASP promoted mainly the absorption and translocation of potassium (K), calcium (Ca), and magnesium (Mg), which greatly exerted physiological roles. However, the variation trends of Cu and Cd under normal soil conditions contrasted with those under stress conditions. With respect to essential elements other than K, Ca, and Mg, PASP mostly restrained their absorption but promoted their translocation. The regulatory mechanism of PASP differed between the combined stress conditions and normal soil conditions. Under the combined stress conditions, PASP seemed to mainly promote these advantageous factors that exert physiological regulatory functions. Under normal soil conditions, PASP mainly acted as a biological stimulant or signaling molecule for increased nutrient eff iciency, which caused greater biomass productivity.

    Keywords: tomato seedlings, polyaspartic acid, Cu+Cd combined stress

    1. lntroduction

    Heavy metals are prevalent in modern cities due to rapid urbanization and industrial development (Liu et al. 2016; Pan 2018). In recent years, due to the unnecessary applications of pesticides and organic and chemical fertilizers as well as industrial waste, the content of heavy metals in agricultural soils has risen. The main pollutants are cadmium (Cd), nickel (Ni), copper (Cu), arsenic (As), mercury (Hg), lead (Pb) and so on (EPMLR 2014). As an essential trace element, Cu is also a heavy metal that is toxic to plants when absorbed in excess. Cd is a wellknown and widespread heavy metal (Xu et al. 2010) and is considered the most toxic pollutant in the soil (Satarug et al. 2003; Wei and Zhou 2006). Although Cu and Cd are not typically associated metals, in the soil, they often exist synchronously in the form of a compound pollutant (Wang et al. 2016). Cu and Cd in agricultural soils can enter into plants, ultimately leading to severe threats to human health via food consumption. Therefore, establishment of remediation programs to reduce the risk through the soil-food-human pathway is urgent.

    Polyaspartic acid (PASP) is a type of fertilizer synergist with carboxylic acid side chains; PASP is completely biodegradable and environmentally friendly. Previous studies have shown that PASP or PASP-urea can enhance plant nutrient-absorbing ability as well as the growth rate, biomass, grain yield and quality when applied to corn, rice, mustard green and other plants (Koskan et al. 1999; King et al. 2012; Deng et al. 2015). Moreover, as an extraction agent, PASP could effectively separate the Pb2+and Cd2+in sludge, and the exchange rate reached 90% (Zhu et al. 2005). Thus, PASP can promote plant growth directly or indirectly by chelating heavy metal ions to reduce biological toxicity. However, the effects of PASP can differ depending on the fertility status of the soil. Therefore, this experiment aimed to investigate the responsive regularity of PASP applied to tomato seedlings under Cu+Cd combined stress and normal soil conditions to provide theoretical evidence for fertilizing on contaminated soil.

    2. Materials and methods

    2.1. Experimental description

    Tomato (Solanum lycopersicum L.) variety Zhongshu 4 was used in this study. The tested soils were collected from the surface layer (0-20 cm) of the test area. The soil type was brown earth, whose basic properties are shown in Table 1.

    A pot cultivation experiment was conducted in a greenhouse (natural light; 25 to 32°C during the day and 19 to 26°C during the night; 75% relative humidity). Four different treatments were applied: (1) control (CK); (2) Cu+Cd; (3) Cu+Cd+PASP; and (4) PASP. Exogenous Cu and Cd were applied evenly to the soil as solutions in the form of CuCl2·2H2O and Cd Cl2·2.5H2O; the concentrations were 500 and 8 mg kg-1, respectively. After they were polluted, the soils were air-dried, mixed thoroughly, sifted through a 40-mesh screen and then added to plastic pots (4.0 kg pot-1). The relative water content was maintained at 80% and selfbalanced for 3 wk. Before f ield planting, the available Cu and Cd were 264.09 and 7.55 mg kg-1, respectively. On March 10, tomato seeds were sown into plug trays. On April 8, at which point the tomato seedlings had developed f ive or six true leaves, the seedlings displaying uniform growth vigor were selected for transplantation to plastic pots (Φmax=22.5 cm, Φmin=16.3 cm, H=19.5 cm); one seedling was transplanted per pot, and each treatment consisted of eight pots. When the seedlings developed seven or eight true leaves, the plants were treated with PASP.

    Previous experiments indicated that plants grew better when their leaves were treated with PASP sprays than when their roots were treated with PASP soil applications. A practical concentration of PASP was 700 mg L-1. The seedlings were sprayed with 100 mL pot-1PASP once every other day; the CK seedlings were sprayed with water. All pots were arranged randomly. After 20 days, the seedlings were harvested and washed thoroughly with running tap water followed by distilled water for 3 min. The biomass (fresh weight (FW)) was measured directly with an electronic balance and then heated to 105°C for 30 min to terminate enzyme activity, after which the biomass was subjected to constant drying at 70°C until the weight became constant. Afterward, the biomass was milled, sieved, sealed and preserved.

    Table 1 The physical and chemical properties of the potted soil

    2.2. Determination of the physical and chemical properties of soil

    The p H, electrical conductivity, available nitrogen (N), available phosphorus (P), and available potassium (K) were analyzed in accordance with previous methods (Bao 2002).

    2.3. Determination of the root activity of and chlorophyll content in plants

    The root ac tivity was d etermined by the 2,3,5- triphenyltetrazolium chloride (TTC) dyeing method (Wang et al. 2016), and the chlorophyll content was determined by the 80% acetone extraction method.

    2.4. Determination of Cu and Cd content in plants

    Plant samples were digested in HNO3-HClO4(4:1, v/v), and the f iltrate was analyzed to determine the content of Cu and Cd by an atomic absorption spectrophotometer (Shimadzu Corporation AA7000).

    2.5. Analysis of N, P and K

    Some plant samples were digested with H2SO4-H2O2. The N content was determined by Kjeldahl azotometer, the P content was determined by the color comparison method with ammonium vanadate-molybdate, and the K content was determined by f lame photometry.

    2.6. Analysis of Ca, Mg, Fe, Zn, and manganese

    Some plant samples were digested with HNO3-HClO4(4:1, v/v), and the f iltrates were diluted at various times to determine the content of Ca, Mg, Fe, Zn, Mn via an atomic absorption spectrophotometer (Shimadzu AA-7000) (Lu 2000).

    2.7. Statistical analysis

    Microsoft Excel software was used for data processing and f iguring, and the least signif icant difference (LSD) was used for multiple comparisons between different treatment means.

    3. Results

    3.1. Growth potential of tomato seedlings under different Cu and Cd treatments

    Fig. 1-A and B show that the effects of different Cu, Cd, and PASP treatments on tomato growth were essentially similar. The plant height and stem diameter of tomato were clearly restricted by Cu+Cd combined stress, and exogenous PASP could not effectively ameliorate the negative effects. Spraying PASP alone had no obvious effects on plant height but notably promoted stem diameter growth, which was benef icial to the development of robust seedlings.

    Fig. 1 The growth vigor of tomato seedlings under different physiological conditions. FW, fresh weight. CK, control; PASP, polyaspartic acid. Different letters indicate signif icant differences at the 5% level. The error bars indicate SE (n=3).

    Compared with that of the CK seedlings, the root biomass of the seedlings subjected to Cu+Cd combined stress signif icantly decreased (Fig. 1-C). However, spraying PASP signif icantly alleviated the root growth inhibition. A similar trend was observed in the aboveground biomass. Under normal soil conditions, 700 mg L-1PASP signif icantly promoted both the root and aboveground growth of tomato plants. This f inding indicated that PASP could somewhat alleviate the damage caused by heavy metals (Cu+Cd) and that the enhancement effect was more apparent under normal growth conditions.

    3.2. Root activity of and chlorophyll content in tomato seedlings under different conditions

    As shown in Fig. 2-A, compared with that of the CK seedlings, the root activity of tomato seedlings treated with Cu+Cd combined stress markedly decreased by 26.94%. However, the inhibitory effect diminished after the spraying of exogenous PASP, and the root activity recovered to nearly the same level as that of the CK seedlings. Under normal growth conditions, spraying PASP signif icantly increased the root activity (57.02% higher activity than that of the CK seedlings), which indicated that PASP had a strong effect on restoring the root function of tomato seedlings.

    As shown in Fig. 2-B, compared with the CK treatment, the Cu+Cd treatment caused a downward trend in chlorophyll content. Although spraying PASP could clearly counteract the decline, the chlorophyll content still did not return to the level of chlorophyll content in the CK treatment under combined stress. However, little difference was found in chlorophyll content between the PASP treatment and CK treatment. Thus, PASP might exert regulatory functions, especially concerning the synthesis of chlorophyll under Cu+Cd combined stress.

    3.3. Absorption and distribution of Cu in tomato seedlings under different Cu and Cd treatments

    Table 2 shows the variation trend of Cu under different treatments. Under Cu+Cd combined stress, the Cu content in each organ markedly increased. In the roots, Cu content sharply increased to 2.91 times that of the CK. The distribution ratio showed that the excessive amount of Cu which was passively absorbed was mainly immobilized in the roots. The addition of 700 mg L-1PASP clearly relieved the trend of increasing Cu content and inhibited excessive Cu translocation to the leaves.

    The absorption and translocation of Cu each exhibited vastly different trends in response to PASP treatment. Under normal growth conditions, applying PASP signif icantly restricted roots from absorbing Cu from the media (only 23.45% of that of the CK) but promoted limited Cu translocation from the roots to aboveground parts, which caused 60.06% of Cu to be distributed in the leaves. The regulatory mechanism of PASP therefore clearly differed between the combined stress and normal conditions.

    3.4. Absorption and distribution of Cd in tomato seedlings under different treatments

    Fig. 2 The root activity of and chlorophyll content in tomato seedlings under different treatments. CK, control; PASP, polyaspartic acid. Different letters mean signif icant differences at the 5% level. The error bars indicate SE (n=3).

    Table 2 The accumulation and distribution of copper in tomato plants

    Table 3 The accumulation and distribution of cadmium in tomato seedlings

    Compared to the CK treatment, under the combined stress treatment, the Cd content markedly increased, up to 35.8, 63.6 and 28.8 times greater in the roots, shoots and leaves, respectively. To some extent, adding PASP could restrict the absorption and translocation of Cd but could not reverse the trend of accumulation. The excessive amounts of Cd passively absorbed tended to be stored in the roots and shoots. Under normal growth conditions, spraying PASP could strongly reduce the absorption and accumulation of Cd. Furthermore, 69.81% of the limited Cd was distributed in the leaves. This phenomenon was similar for Cu, despite the translocation eff iciency of Cd being much higher than that of Cu.

    3.5. Absorption and distribution of N, P, and K in tomato seedlings under different Cu and Cd treatments

    As shown in Fig. 3-A, compared to the CK treatment, the Cu+Cd combined stress treatment promoted root absorption of N from the media and enhanced the translocation of N from the roots to leaves. However, adding PASP exhibited no clear effects. Under normal growth conditions, adding PASP evidently reduced the absorption and translocation of N, especially in the leaves, in which the N accumulation decreased by 9.43%.

    As shown in Fig. 3-B, the absorption and translocation of P were restricted by Cu+Cd combined stress, and exogenous PASP could effectively relieve this restriction in the roots; however, in the leaves, the decrease was enhanced. Applying PASP separately signif icantly reduced the P content in the roots and leaves.

    As shown in Fig. 3-C, the K content was noticeably restricted in the leaves by only Cu+Cd combined stress, and exogenous PASP effectively relieved the adverse effects in the leaves and stems. However, under normal soil conditions, spraying PASP resulted in a progressive trend in the absorption and translocation of K, but this trend was signif icant only in the roots and stems.

    3.6. Absorption of other similarly charged elements in tomato seedlings under different Cu and Cd treatments

    Fig. 3 The content and accumulation of N, P, and K in tomato plants under different Cu and Cd treatments. CK, control; PASP, polyaspartic acid. Different letters mean signif icant differences at the 5% level. The error bars indicate SE (n=3).

    As shown in Table 4, compared to the CK treatment, the Cu+Cd combined stress treatment markedly inhibited the translocation of Fe from the roots to the leaves, which led to 15.07 and 34.83% reductions in Fe content in the stems and leaves, respectively. PASP foliar sprays effectively promoted the translocation of stored Fe from the roots to leaves, which resulted in increased Fe contents of 165.12 and 31.4% in the stems and leaves under combined stress, respectively. However, spraying PASP separately caused all Fe contents to decrease (21.4, 11.42, and 31.96% in the roots, stems, and leaves, respectively).

    The variation trend of Mn was similar to that of Fe. The Mn content decreased by 36.59, 33.51, and 27.47% in the roots, stems and leaves, respectively; these decreases were greater than those of the Fe content under Cu+Cd combined stress, and the repairing effect of PASP was ref lected mainly in the stems (40.86%). Under normal growth conditions, PASP signif icantly reduced the absorption and translocation of Mn, especially in the roots, in which the Mn content decreased by 34.22%.

    Compared with the CK treatment, the combined stress treatment signif icantly reduced the absorption and translocation of Zn. Exogenous PASP could eff iciently alleviate the inhibition effect but could not restore the Zn content to that in the CK treatment. Under normal soil conditions, spraying PASP also caused the Zn content to clearly decrease by 37.01 and 62.30% in the roots and leaves, respectively.

    A summary of the above analysis shows that, under excessive Cu+Cd stress, the essential elements that have a similar charge as that of both Cu and Cd were apparently competitively inhibited; to some degree, exogenous PASP could alleviate this inhibition effect. Under normal conditions, without exception, exogenous PASP reduced the absorption of these nutrient elements.

    However, the combined Cu+Cd stress promoted the absorption and translocation of Ca by up to 24.95, 51.9, and 25.2% in the roots, stems and leaves, respectively. In addition, adding PASP maintained the increasing trend. Under normal conditions, exogenous PASP inhibited the absorption and translocation of Ca by 12.99, 18.76, and 16.36% in the roots, stems and leaves, respectively. The variation trend of Mg was similar to that of Ca under both the combined stress and normal conditions.

    4. Discussion

    PASP, which contains a large number of carboxylic groups and amide groups among its molecular chains (Tomida et al. 1997), strongly absorbs ions that reduce nutrient loss and improved nutrient accumulation in the soil (Kinnersley et al. 1997). Therefore, increased levels of available nutrients in the root feeding zone occur in response to PASP applications, and more eff icient nutrient use is achieved; in addition, the availability of toxic ions (such as Cr6+) can decrease (Koskan et al. 1999; Du et al. 2011; Fu et al. 2017). In this experiment, under Cu+Cd combined stress, spraying PASP on the leaves also strengthened the resistance and tolerance of tomato seedlings against heavy metal toxicity, clearly restoring plant biomass, especially that of the roots, much higher than that of the CK seedlings. However, for plant height and stem diameter, the relieving effect exhibited just a gradually increasing trend, which was likely because the treatment time was short. However, under normal conditions, foliar spraying of PASP increased dry matter accumulation. Although plant height changed little in response to PASP, root activity was strongly promoted, and stem diameter markedly increased. These results indicated that the roots could function with increased eff iciency to absorb and translocate mineral nutrients.

    Table 4 The content and accumulation of other cations in tomato plants under different Cu and Cd treatments

    Root activity was closely related to the whole growth environment; the root activity directly ref lected root absorption function but was easily negatively affected by heavy metal stress (Hawrylak-Nowak et al. 2015). In this study, regardless of the stress conditions, spraying PASP signif icantly promoted root activity. Moreover, in the aboveground parts, the suff icient amount of detected chlorophyll in the leaf conf irmed that the plants could function properly (Singh et al. 2007). Both of these aspects ensured that the tomato seedlings could perform normal metabolic activity, which led to the recovery of or the increase in root biomass.

    The effects of PASP on other mineral elements varied. For Cu and Cd, under excessive stress, PASP played a regulatory role in preventing excessive toxic ions from being absorbed and translocated mineral nutrients to the leaves, which ensured normal cell protoplasm function as much as possible. However, under normal soil conditions, PASP sharply prevented mineral absorption, but to a greater extent, PASP limited the translocation of Cu and Cd to the leaves. This phenomenon was inconsistent with previous research results (Leng 2005). Here, the results seem to imply that PASP actually functions somewhat as a biological stimulant under nonstress conditions (Pamela Calvo et al. 2014).

    Cu+Cd combined stress clearly restricted the absorption of the essential elements N, P, Fe, Mn, and Zn, while spraying PASP effectively alleviated the inhibition and positively regulated the translocation of these ions to the leaves. Under Cu+Cd combined stress, the absorption of Fe increased in response to PASP, which was consistent with the trend of chlorophyll content. Under normal soil conditions, spraying PASP exhibited a passive role in the absorption and translocation of some trace elements. Regardless of the presence of stress, PASP always positively affected the absorption and translocation of only K+. This result indicates that PASP exhibits regulatory ability by activating the physiological mechanism of K+(Marschner 2013). Unintentionally combined stress promoted the absorption and translocation of Ca and Mg, and PASP intensif ied this trend. This result was likely due to the special relation between Ca and PASP. As a green scale inhibitor or desalinator (Shilpa et al. 2014), the carboxylic groups among the PASP polymer are the main functional groups that inhibit the formation of calcium carbonate and calcium sulfate scale, while the hydroxylic groups and acylamino groups are the main functional groups that inhibit the formation of calcium phosphate (Chen et al. 2015). These results provided a fundamental understanding of why suff icient amounts of active Ca are essential for growth under abiotic stress (Marschner 2013). Under normal conditions, PASP clearly reduced the absorption and translocation of Ca and Mg.

    Therefore, from a general perspective of the above elements, the variation among the essential elements was extremely large. When exposed to compound heavy metal stress, some elements are competitively inhibited due to their similar chemical characteristics (Tanhan et al. 2007; Hawrylak-Nowak et al. 2015). Some elements, especially essential key elements (such as N and P), were strongly limited. PASP could somewhat relieve the negative effects but barely restored the contents to those in the CK treatment. When exposed to combined stress, K, Ca and Mg exhibited more physiological function and osmotic adjustment, which helped maintain the integrity of the structure and function of the cell (Marschner 2013).

    It is well known that PASP can chelate Ca, Mg, Cu, and Fe as well as other polyvalent metal ions (Koskan and Low 1992). The functional groups of the amino acids on the end and the carboxylic acids on the side chains can coordinate with metal cations and encapsulate them into a “hole”, which disperses and stabilizes metal cations in solution (Gutierrez et al. 1999). However, spraying PASP alone on the leaf surface reduced the absorption of some mineral elements under normal soil conditions, but root activity, stem diameter and plant biomass were instead promoted; these indexes are key indicators of seedling quality. Furthermore, the tomato seedlings showed no obvious nutrient def iciency symptoms, which meant that their nutrient use eff iciency increased. This phenomenon is inconsistent with previous reports on PASP as a fertilizer synergist (Du et al. 2011; Deng et al. 2014, 2015). In addition, the response mechanism distinctly differed between PASP foliar sprays and root applications.

    5. Conclusion

    The above evidence suggests that, in a healthy soil environment, PASP plays a role similar to a biological stimulant or signaling molecule to regulate the absorption and translocation of mineral nutrients, whereas under stress conditions, PASP acts more like a fertilizer synergist. However, additional studies are needed to elucidate the response mechanism.

    Acknowledgements

    This work was supported by the Project of Shandong Province Higher Educational Science and Technology Program, China (J16LF02), the Funds of Shandong “Double Tops” Program, China (SYL2017YSTD01), and the Major Scientif ic and Technological Innovation Project in Shandong Province, China (2018CXGC0209).

    国产精品不卡视频一区二区| 色5月婷婷丁香| 人人妻人人澡人人爽人人夜夜 | 一级毛片aaaaaa免费看小| 在线看三级毛片| 好男人在线观看高清免费视频| 我要看日韩黄色一级片| 日韩欧美一区二区三区在线观看| 不卡一级毛片| 又黄又爽又免费观看的视频| 欧美激情国产日韩精品一区| 亚洲欧美日韩东京热| av中文乱码字幕在线| 一级毛片电影观看 | 精品乱码久久久久久99久播| 禁无遮挡网站| 中文字幕久久专区| 亚洲一区二区三区色噜噜| 久久久久久久久大av| 欧美zozozo另类| 欧美丝袜亚洲另类| 国产精品亚洲美女久久久| 99久久久亚洲精品蜜臀av| 色吧在线观看| 亚洲欧美清纯卡通| 成人美女网站在线观看视频| 精品一区二区三区人妻视频| 精品久久国产蜜桃| 1024手机看黄色片| 免费一级毛片在线播放高清视频| 欧美又色又爽又黄视频| 日韩欧美免费精品| 女的被弄到高潮叫床怎么办| 一个人看的www免费观看视频| 美女免费视频网站| 少妇裸体淫交视频免费看高清| 国产日本99.免费观看| 成人欧美大片| 国产精品久久久久久亚洲av鲁大| 偷拍熟女少妇极品色| 非洲黑人性xxxx精品又粗又长| 99精品在免费线老司机午夜| 97碰自拍视频| 国产精品女同一区二区软件| 欧美极品一区二区三区四区| 免费看光身美女| 色在线成人网| 日日摸夜夜添夜夜爱| 亚洲精品456在线播放app| 日韩欧美在线乱码| 日韩人妻高清精品专区| a级毛片a级免费在线| 成人性生交大片免费视频hd| 日韩一区二区视频免费看| av在线蜜桃| 亚洲自偷自拍三级| 成人av在线播放网站| 人妻丰满熟妇av一区二区三区| 久久精品91蜜桃| 免费电影在线观看免费观看| 中国美女看黄片| 别揉我奶头 嗯啊视频| 成年版毛片免费区| 深夜精品福利| 麻豆精品久久久久久蜜桃| 麻豆精品久久久久久蜜桃| 免费黄网站久久成人精品| 午夜免费男女啪啪视频观看 | 美女免费视频网站| 欧美bdsm另类| 日本成人三级电影网站| 精品少妇黑人巨大在线播放 | 性插视频无遮挡在线免费观看| 国产精品女同一区二区软件| 在线观看美女被高潮喷水网站| 99九九线精品视频在线观看视频| 综合色丁香网| 日韩成人av中文字幕在线观看 | 欧美区成人在线视频| 国内揄拍国产精品人妻在线| 国产一区二区亚洲精品在线观看| 在线观看一区二区三区| 在线观看一区二区三区| 久久精品国产自在天天线| 久久精品国产清高在天天线| 亚洲18禁久久av| 长腿黑丝高跟| 国产一区二区亚洲精品在线观看| 免费人成视频x8x8入口观看| 一级毛片电影观看 | 国内精品久久久久精免费| 久久久精品大字幕| 天堂网av新在线| 91在线观看av| 日日摸夜夜添夜夜添小说| a级一级毛片免费在线观看| 精品少妇黑人巨大在线播放 | 国产精品永久免费网站| 国产爱豆传媒在线观看| 国产黄色小视频在线观看| 亚洲av电影不卡..在线观看| 免费av不卡在线播放| 久久久久久伊人网av| 午夜精品在线福利| 久久亚洲国产成人精品v| 亚洲成人精品中文字幕电影| 在线观看午夜福利视频| 亚洲在线观看片| 一区二区三区高清视频在线| a级毛片免费高清观看在线播放| 美女 人体艺术 gogo| 免费av观看视频| 村上凉子中文字幕在线| 午夜老司机福利剧场| 亚洲人成网站高清观看| 老熟妇仑乱视频hdxx| 欧美性猛交黑人性爽| 又爽又黄无遮挡网站| 欧美不卡视频在线免费观看| 久久中文看片网| 1024手机看黄色片| 天天一区二区日本电影三级| 日韩制服骚丝袜av| 国产精品一区www在线观看| 赤兔流量卡办理| 国产三级在线视频| 亚洲精品影视一区二区三区av| 国产在视频线在精品| 永久网站在线| 高清日韩中文字幕在线| 久久6这里有精品| 久久久久九九精品影院| 狂野欧美白嫩少妇大欣赏| 老女人水多毛片| 精品久久久久久成人av| 国产视频内射| 晚上一个人看的免费电影| 国产精品永久免费网站| 真实男女啪啪啪动态图| 美女被艹到高潮喷水动态| 久久久久国产精品人妻aⅴ院| 日本黄色视频三级网站网址| 精品福利观看| 欧美+亚洲+日韩+国产| 丰满的人妻完整版| АⅤ资源中文在线天堂| 久久综合国产亚洲精品| av卡一久久| 在线观看午夜福利视频| 精品无人区乱码1区二区| 国产久久久一区二区三区| 人人妻人人看人人澡| 国产高清不卡午夜福利| 俄罗斯特黄特色一大片| 午夜久久久久精精品| 国产成人精品久久久久久| 97在线视频观看| 晚上一个人看的免费电影| 熟女电影av网| 国产黄色小视频在线观看| 国产av一区在线观看免费| 大香蕉久久网| 神马国产精品三级电影在线观看| 亚洲av免费在线观看| 国产一区二区激情短视频| 我要搜黄色片| 三级毛片av免费| 九九爱精品视频在线观看| 欧美国产日韩亚洲一区| 国内久久婷婷六月综合欲色啪| av专区在线播放| 国产白丝娇喘喷水9色精品| 一级黄色大片毛片| 日韩欧美精品v在线| 午夜a级毛片| 国产真实伦视频高清在线观看| 久久亚洲精品不卡| АⅤ资源中文在线天堂| 亚洲高清免费不卡视频| 夜夜夜夜夜久久久久| 成人欧美大片| 亚洲美女黄片视频| 午夜精品在线福利| 网址你懂的国产日韩在线| 亚洲av成人av| 午夜福利成人在线免费观看| 久久欧美精品欧美久久欧美| 亚洲va在线va天堂va国产| 看片在线看免费视频| 在线观看一区二区三区| 麻豆精品久久久久久蜜桃| .国产精品久久| 国产一区二区在线av高清观看| 欧美中文日本在线观看视频| 麻豆久久精品国产亚洲av| 美女xxoo啪啪120秒动态图| 直男gayav资源| 在线观看av片永久免费下载| 亚洲精品国产av成人精品 | av在线天堂中文字幕| 亚洲不卡免费看| 国产午夜福利久久久久久| 国产男人的电影天堂91| or卡值多少钱| 久久久精品欧美日韩精品| 精品欧美国产一区二区三| 亚洲第一电影网av| 日韩欧美国产在线观看| 亚洲在线观看片| 免费看av在线观看网站| 色av中文字幕| 午夜久久久久精精品| 成年版毛片免费区| 嫩草影视91久久| www.色视频.com| 亚洲无线在线观看| 亚洲成人久久爱视频| 亚洲在线观看片| 久久精品91蜜桃| 97人妻精品一区二区三区麻豆| 日韩强制内射视频| 高清毛片免费观看视频网站| 亚洲人成网站在线播| 国产精品野战在线观看| 九九在线视频观看精品| 美女免费视频网站| 欧美性感艳星| 少妇人妻精品综合一区二区 | 岛国在线免费视频观看| 欧美色视频一区免费| 久久久精品大字幕| 亚洲专区国产一区二区| www.色视频.com| 日日干狠狠操夜夜爽| 最近手机中文字幕大全| 亚洲四区av| 国产亚洲欧美98| 国产精品福利在线免费观看| 在现免费观看毛片| 国产视频一区二区在线看| 黄色视频,在线免费观看| 亚洲天堂国产精品一区在线| 男人舔女人下体高潮全视频| 国产麻豆成人av免费视频| 在线a可以看的网站| 日韩强制内射视频| 国产av麻豆久久久久久久| 丰满的人妻完整版| 欧美3d第一页| 又粗又爽又猛毛片免费看| 一级毛片我不卡| 内射极品少妇av片p| 精品久久久久久久久av| 亚洲av电影不卡..在线观看| 九九在线视频观看精品| 国产国拍精品亚洲av在线观看| 最近在线观看免费完整版| 大又大粗又爽又黄少妇毛片口| 国产精品一区二区性色av| 美女大奶头视频| 亚洲精品国产成人久久av| 一区二区三区四区激情视频 | 欧美丝袜亚洲另类| 国产高清三级在线| 色综合色国产| 一级a爱片免费观看的视频| 久久精品影院6| 在线观看午夜福利视频| 欧美另类亚洲清纯唯美| 中文亚洲av片在线观看爽| 日本爱情动作片www.在线观看 | 欧美一区二区亚洲| 国产精品伦人一区二区| 黄色日韩在线| 国产精品一及| 日本欧美国产在线视频| 精品一区二区三区av网在线观看| 国产高清不卡午夜福利| 五月伊人婷婷丁香| 国产高清视频在线观看网站| 久久久久久国产a免费观看| 亚洲不卡免费看| 老熟妇仑乱视频hdxx| 免费av不卡在线播放| 成人高潮视频无遮挡免费网站| 人人妻,人人澡人人爽秒播| 亚洲av.av天堂| 免费看美女性在线毛片视频| 人妻少妇偷人精品九色| 搡老熟女国产l中国老女人| 久久精品影院6| 中文字幕人妻熟人妻熟丝袜美| 亚洲av免费在线观看| 精品99又大又爽又粗少妇毛片| 国产三级中文精品| 亚洲最大成人手机在线| 国产视频一区二区在线看| 日日摸夜夜添夜夜爱| av在线亚洲专区| 哪里可以看免费的av片| 国产aⅴ精品一区二区三区波| 少妇被粗大猛烈的视频| 蜜桃亚洲精品一区二区三区| 欧美日本亚洲视频在线播放| 秋霞在线观看毛片| 在线观看av片永久免费下载| 老司机影院成人| 插逼视频在线观看| videossex国产| 国产精品一区二区三区四区免费观看 | 亚洲精品国产av成人精品 | 欧美色视频一区免费| 亚洲人成网站在线播放欧美日韩| 日韩高清综合在线| 九九在线视频观看精品| 午夜免费激情av| 变态另类成人亚洲欧美熟女| av卡一久久| 久久久久国产精品人妻aⅴ院| 一级毛片久久久久久久久女| 日韩成人伦理影院| 嫩草影院精品99| 赤兔流量卡办理| 亚洲精品粉嫩美女一区| 天堂av国产一区二区熟女人妻| 在线免费观看的www视频| 久久精品国产鲁丝片午夜精品| 国产一区二区在线观看日韩| 国产v大片淫在线免费观看| 自拍偷自拍亚洲精品老妇| 美女 人体艺术 gogo| 国产高潮美女av| 久久久色成人| 色哟哟哟哟哟哟| 插阴视频在线观看视频| 九九在线视频观看精品| 99久久精品国产国产毛片| 国产视频一区二区在线看| 嫩草影院入口| 九九在线视频观看精品| 久久国内精品自在自线图片| 三级国产精品欧美在线观看| 亚洲欧美中文字幕日韩二区| 日韩欧美 国产精品| 99久久精品国产国产毛片| 高清午夜精品一区二区三区 | 亚洲久久久久久中文字幕| 日韩中字成人| 最新在线观看一区二区三区| 精品人妻视频免费看| 99热这里只有是精品在线观看| 国产精品久久久久久亚洲av鲁大| 桃色一区二区三区在线观看| 国产真实伦视频高清在线观看| 国产69精品久久久久777片| 久久欧美精品欧美久久欧美| 夜夜夜夜夜久久久久| 亚洲真实伦在线观看| 久久精品国产亚洲网站| 亚洲精品一区av在线观看| 欧美色欧美亚洲另类二区| 日韩人妻高清精品专区| 在线看三级毛片| 国产男靠女视频免费网站| 97超级碰碰碰精品色视频在线观看| 亚洲精品日韩在线中文字幕 | 18+在线观看网站| 91久久精品国产一区二区三区| 赤兔流量卡办理| 一级毛片电影观看 | 在线看三级毛片| 蜜臀久久99精品久久宅男| 久久国内精品自在自线图片| 免费看光身美女| 露出奶头的视频| 国产精品一区二区免费欧美| 美女免费视频网站| 精品人妻熟女av久视频| 日日啪夜夜撸| 99热全是精品| 精品人妻视频免费看| 国产精品久久久久久久久免| 国产不卡一卡二| 亚洲av电影不卡..在线观看| 免费av毛片视频| 级片在线观看| 国产精品人妻久久久影院| 国产色婷婷99| 国产一区二区亚洲精品在线观看| 中国美白少妇内射xxxbb| 黄色视频,在线免费观看| 国产精品亚洲美女久久久| 精品免费久久久久久久清纯| 欧美不卡视频在线免费观看| 俺也久久电影网| 婷婷色综合大香蕉| 熟女人妻精品中文字幕| 国产乱人视频| 非洲黑人性xxxx精品又粗又长| av在线观看视频网站免费| 性欧美人与动物交配| 精品人妻视频免费看| 精品日产1卡2卡| 国产不卡一卡二| 欧美国产日韩亚洲一区| 免费电影在线观看免费观看| 亚洲欧美日韩高清在线视频| a级毛片a级免费在线| 国产探花在线观看一区二区| a级毛片免费高清观看在线播放| 免费av观看视频| 免费观看人在逋| 久久亚洲国产成人精品v| 床上黄色一级片| 久久精品国产鲁丝片午夜精品| 一级a爱片免费观看的视频| 久久久国产成人免费| 欧美人与善性xxx| 国产真实伦视频高清在线观看| 超碰av人人做人人爽久久| 国产 一区 欧美 日韩| 国产精品久久久久久亚洲av鲁大| 激情 狠狠 欧美| 亚洲国产精品国产精品| 国产亚洲精品久久久久久毛片| 最近视频中文字幕2019在线8| 精品久久久久久久久久久久久| 无遮挡黄片免费观看| 春色校园在线视频观看| 中文资源天堂在线| 深夜精品福利| 内地一区二区视频在线| 国产一区二区三区av在线 | 亚洲人与动物交配视频| 婷婷精品国产亚洲av| 在线观看美女被高潮喷水网站| 午夜日韩欧美国产| 少妇的逼好多水| 十八禁国产超污无遮挡网站| 色综合色国产| 午夜视频国产福利| 18禁黄网站禁片免费观看直播| 少妇人妻精品综合一区二区 | 狂野欧美白嫩少妇大欣赏| 在线观看av片永久免费下载| 精品一区二区三区视频在线| av.在线天堂| 毛片一级片免费看久久久久| 精品少妇黑人巨大在线播放 | 亚洲精品在线观看二区| 最近在线观看免费完整版| 成人av一区二区三区在线看| 一本一本综合久久| 人妻夜夜爽99麻豆av| 日韩欧美精品免费久久| 日韩,欧美,国产一区二区三区 | 亚洲色图av天堂| 亚洲av一区综合| 久久久久免费精品人妻一区二区| 精品久久久久久久久av| 99热这里只有是精品50| а√天堂www在线а√下载| 草草在线视频免费看| 午夜亚洲福利在线播放| 亚洲av成人精品一区久久| 一a级毛片在线观看| av女优亚洲男人天堂| 在线观看免费视频日本深夜| 91久久精品国产一区二区成人| 日韩欧美在线乱码| 国产精品一及| 又爽又黄a免费视频| 日本 av在线| 亚洲精品456在线播放app| 99国产极品粉嫩在线观看| 欧美色视频一区免费| 国产熟女欧美一区二区| 69av精品久久久久久| 欧美日本视频| 少妇的逼好多水| 联通29元200g的流量卡| 日本精品一区二区三区蜜桃| 欧洲精品卡2卡3卡4卡5卡区| 亚洲美女黄片视频| aaaaa片日本免费| 日产精品乱码卡一卡2卡三| 久久人人爽人人片av| 久久久久久九九精品二区国产| 成人av在线播放网站| 人妻夜夜爽99麻豆av| 亚洲欧美日韩高清专用| 日本-黄色视频高清免费观看| 久久久色成人| 人妻夜夜爽99麻豆av| 国产片特级美女逼逼视频| 日本黄色视频三级网站网址| 日本一二三区视频观看| 在线天堂最新版资源| 午夜老司机福利剧场| 亚洲经典国产精华液单| 69av精品久久久久久| 少妇高潮的动态图| 亚洲七黄色美女视频| 国产精品99久久久久久久久| 在线观看美女被高潮喷水网站| av在线亚洲专区| 我要搜黄色片| 不卡视频在线观看欧美| 欧美日韩乱码在线| 尾随美女入室| 我要看日韩黄色一级片| 看片在线看免费视频| 国产国拍精品亚洲av在线观看| 中文字幕久久专区| 免费不卡的大黄色大毛片视频在线观看 | 精品欧美国产一区二区三| 不卡一级毛片| 欧美色视频一区免费| 99久久久亚洲精品蜜臀av| av女优亚洲男人天堂| 欧美一区二区精品小视频在线| 久久久国产成人免费| 日本黄大片高清| 久久国内精品自在自线图片| 1000部很黄的大片| 在现免费观看毛片| 99久久久亚洲精品蜜臀av| 乱系列少妇在线播放| 久久精品人妻少妇| 中文字幕精品亚洲无线码一区| 亚洲精品亚洲一区二区| 中文字幕精品亚洲无线码一区| 国产精品久久久久久亚洲av鲁大| 少妇熟女欧美另类| 午夜影院日韩av| 成人鲁丝片一二三区免费| 亚洲乱码一区二区免费版| 欧美丝袜亚洲另类| 久久人人精品亚洲av| 免费看日本二区| 国产不卡一卡二| 国产久久久一区二区三区| 高清日韩中文字幕在线| 精品一区二区三区av网在线观看| 国产男人的电影天堂91| 日日摸夜夜添夜夜添小说| 乱人视频在线观看| 久久久久免费精品人妻一区二区| 午夜亚洲福利在线播放| 色综合色国产| 97热精品久久久久久| 我的老师免费观看完整版| 人妻久久中文字幕网| 长腿黑丝高跟| 国产白丝娇喘喷水9色精品| 51国产日韩欧美| 免费av毛片视频| av在线亚洲专区| 亚洲av免费高清在线观看| 国产av在哪里看| 国产精品一区二区免费欧美| 日日干狠狠操夜夜爽| 我的老师免费观看完整版| 精品99又大又爽又粗少妇毛片| 久久久久久久午夜电影| 日本成人三级电影网站| 欧美3d第一页| 变态另类丝袜制服| 波野结衣二区三区在线| 桃色一区二区三区在线观看| 亚洲国产欧洲综合997久久,| 国产精品99久久久久久久久| 嫩草影院入口| 国内精品美女久久久久久| 国产中年淑女户外野战色| 成人综合一区亚洲| 精品久久久久久久久亚洲| 中文字幕免费在线视频6| 免费电影在线观看免费观看| av专区在线播放| 美女xxoo啪啪120秒动态图| 老熟妇乱子伦视频在线观看| 亚洲av免费高清在线观看| 无遮挡黄片免费观看| 中文在线观看免费www的网站| 亚洲国产欧美人成| 亚洲av五月六月丁香网| 男人和女人高潮做爰伦理| 最好的美女福利视频网| 亚洲人成网站在线播| 国产黄a三级三级三级人| 搞女人的毛片| 亚洲精品国产av成人精品 | 一级毛片电影观看 | 91麻豆精品激情在线观看国产| 天堂网av新在线| a级毛片免费高清观看在线播放| 久久久久久久久久成人| 18禁在线无遮挡免费观看视频 | 老司机影院成人| 亚洲精品一区av在线观看| 欧美成人免费av一区二区三区| 我的女老师完整版在线观看| 老师上课跳d突然被开到最大视频| 波多野结衣高清作品| 日韩在线高清观看一区二区三区| 欧美在线一区亚洲| 成人特级黄色片久久久久久久| 亚洲成人久久爱视频| 又粗又爽又猛毛片免费看| 特大巨黑吊av在线直播| 久久久久久久久久黄片| 美女被艹到高潮喷水动态| 乱人视频在线观看| 在线观看免费视频日本深夜|