Negative Effects of Butachlor on the Growth and Physiology of Four Aquatic Plants.

The increasing use of herbicides in intelligent agricultural production is driven by the time-consuming nature of manual weeding, as well as its ephemeral effectiveness. However, herbicides like butachlor degrade slowly and can be washed away by rainwater, ultimately flowing into the farm ponds and posing risks to aquatic plants. To identify and recommend superior restoration strategies that effectively address the challenges posed by butachlor, we investigated the impacts of butachlor on the growth and physiology of four common aquatic plants (i.e., Hydrilla verticillata, Ceratophyllum demersum, Potamogeton maackianus, and Myriophyllum aquaticum) and their potential role in mitigating environmental damage by reducing residual herbicide levels. Our findings indicated that M. aquaticum was tolerant to butachlor, exhibiting higher growth rates than other species when exposed to various butachlor concentrations. However, the concentration of butachlor negatively impacted the growth of H. verticillata, C. demersum, and P. maackianus, with higher concentrations leading to more significant inhibitory effects. After a 15-day experimental period, aquatic plants reduced the butachlor residuals in culture mediums across concentrations of 0.5 mg/L, 1 mg/L, and 2 mg/L compared to non-plant controls. Our findings classified P. maackianus as butachlor-sensitive and M. aquaticum as butachlor-tolerant species. This investigation represents novel research aimed at elucidating the contrasting effects of different concentrations of butachlor on four common aquatic species in the agricultural multi-pond system.

Apoplastic histochemical features of plant root walls that may facilitate ion uptake and retention.

We used brightfield and epifluorescence microscopy, as well as permeability tests, to investigate the apoplastic histochemical features of plant roots associated with ion hyperaccumulation, invasion, and tolerance of oligotrophic conditions. In hyperaccumulator species with a hypodermis (exodermis absent), ions penetrated the root apex, including the root cap. By contrast, in non-hyperaccumulator species possessing an exodermis, ions did not penetrate the root cap. In vivo, the lignified hypodermis blocked the entry of ions into the cortex, while root exodermis absorbed ions and restricted them to the cortex. The roots of the hyperaccumulators Pteris vittata and Cardamine hupingshanensis, as well as the aquatic invasives Alternanthera philoxeroides, Eichhornia crassipes, and Pistia stratiotes, contained lignin and pectins. These compounds may trap and store ions before hypodermis maturation, facilitating ion hyperaccumulation and retention in the apoplastic spaces of the roots. These apoplastic histochemical features were consistent with certain species-specific characters, including ion hyperaccumulation, invasive behaviors in aquatic environments, or tolerance of oligotrophic conditions. We suggest that apoplastic histochemical features of the root may act as invasion mechanisms, allowing these invasive aquatic plants to outcompete indigenous plants for ions.

Phenotypic Plasticity in the Structure of Fine Adventitious Metasequoia glyptostroboides Roots Allows Adaptation to Aquatic and Terrestrial Environments.

Metasequoia glyptostroboides (Cupressaceae) is a rare deciduous conifer which grows successfully in both aquatic and terrestrial environments. This tree has a narrow natural distribution in central China but is cultivated worldwide. Using histochemical staining and microscopy (both brightfield and epifluorescent), we investigated whether the phenotypic anatomical and histochemical plasticity in the fine adventitious roots of M. glyptostroboides has promoted the adaptation of this plant to aquatic and terrestrial environments. The fine root development and cortex sloughing of M. glyptostroboides occurs later in aquatic habitats than in terrestrial habitats. Anatomical and histochemical analyses have revealed that the apoplastic barriers in the primary growth of the fine roots consist of the endodermis and exodermis with Casparian bands, suberin lamellae, and secondarily lignified cell walls. There were also lignified phi (Φ) thickenings in the cortex. In both aquatic and terrestrial roots, secondary growth was observed in the vascular cambium, which produced secondary xylem and phloem, as well as in the phellogen, which produced cork. As compared to terrestrial adventitious roots, aquatic adventitious roots had multiple lignified Φ thickenings throughout the cortex, larger air spaces, dilated parenchyma, and dense suberin and lignin depositions in the exodermis. Our results thus indicate that phenotypic plasticity in the anatomical features of the fine adventitious roots, including apoplastic barriers, air spaces, and lignified Φ thickenings, might support the adaptation of M. glyptostroboides to both aquatic and terrestrial environments.

[Characteristics and Evaluation of Heavy Metal Pollution in Vegetables in Guangzhou].

Vegetable is an indispensible component of human daily diet,and contamination of vegetables by heavy metals directly threatens human health.In this study,116 vegetable samples were collected from 12 administrative districts of Guangzhou City for analysis of six heavy metals,Cu,Zn,Pb,Cd,Ni,Cr.A combination of single factor evaluation and Nemero Index analysis was employed to determine specific heavy metals exceeding allowable standards and analyze the characteristics of pollution.Risk of exposure was utilized to assess human health risks originating from eating locally planted vegetables contaminated by heavy metals.The results showed that contents of Cu,Zn in the 8 sorts of vegetables were below the standards of maximum allowable content and the contents of heavy mental Cr of up to 91.67% vegetable samples were higher than their standard.Lettuce sativa var.angustana Irish,Luffa acutangula L.,Lycopersicon esculentum Mill.and Daucus carota L.were the 4 species of Pb exceeding vegetables,with the exceed ratio reaching up to 35.71% and Daucus carota L.exceeded the target value most seriously.Only the content of Cd in Lycopersicon esculentum Mill.was over-standard,with the rate of 31.25%.And the highest rate of over-standard of the content of Ni in 3 species of vegetables,which included Lactuca sativa L.,Ipomoea aquatica Forsk and Brassica parachinensis,reached 8.33%.For the contamination level of the eight kinds of vegetable,Lactuca sativa L.,Ipomoea aquatica Forsk,Brassica parachinensis,Raphanus sativus L.and Daucus carota L.were put into the class of alarming,while Lettuce sativa var.angustana Irish,Luffa acutangula L.and Lycopersicon esculentum Mill.were classified as secure.Heavy metals' comprehensive pollution degree of 4 species of vegetables presented a trend of leafy vegetables >rootstalk vegetables >stem vegetables >solanaceous fruits.Health risk assessment showed that Guangzhou citizens eat more frequently Ipomoea aquatica Forsk and Lactuca sativa L.and Brassica parachinensis were prone to higher accumulation of heavy metals,and the dietary intake of heavy metal Cr might cause harm to human health and intake of Cd would bring potential health risk to the human body.Risk of exposure to heavy metal through oral ingestion of vegetables was proved to be higher for children than adults.

Effect of N and P addition on soil organic C potential mineralization in forest soils in South China.

Atmospheric nitrogen deposition is at a high level in some forests of South China. The effects of addition of exogenous N and P on soil organic carbon mineralization were studied to address: (1) if the atmospheric N deposition promotes soil C storage through decreasing mineralization; (2) if the soil available P is a limitation to organic carbon mineralization. Soils (0-10 cm) was sampled from monsoon evergreen broad-leaved forest (MEBF), coniferous and broad-leaved mixed forest (CBMF), and Pinus massoniana forest (PMF) in Dinghushan Biosphere Reserve (located in Guangdong Province, China). The soils were incubated at 25 degrees C for 45 weeks, with addition of N (NH4NO3 solution) or P (KH2PO4 solution). CO2-C emission and the inorganic N (NH4(+)-N and NO3(-)-N) of the soils were determined during the incubation. The results showed that CO2-C emission decreased with the N addition. The addition of P led to a short-term sharp increase in CO2 emission after P application, and the responses of CO2-C evolution to P addition in the later period of incubation related to forest types. Strong P inhibition to CO2 emission occurred in both PMF and CBMF soils in the later incubation. The two-pool kinetic model was fitted well to the data for C turnover in this experiment. The model analysis demonstrated that the addition of N and P changed the distribution of soil organic C between the labile and recalcitrant pool, as well as their mineralization rates. In our experiment, soil pH can not completely explain the negative effect of N addition on CO2-C emission. The changes of soil inorganic N during incubation seemed to support the hypothesis that the polymerization of added nitrogen with soil organic compound by abiotic reactions during incubation made the added nitrogen retard the soil organic carbon mineralization. We conclude that atmospheric N deposition contributes to soil C accretion in the three subtropical forest ecosystems, however, the shortage of soil available P in CBMF and PMF may also retard soil organic C mineralization.