The Effects Of Graphene On The Germination And Seedling Growth In Rice

Nanotechnology and nanotech products have been widely used in many industries such as microelectrics, photoelectricity, caremics, biological engineering, medicine and chemical engineering, with the high improvement of science and technology. In the past decades, the number of nanotech products has been increased exponentially, and also, the scope and variety is expanding continuously. It is assumed that nanotech products will be used more widely in the next few years. The extensive use of nanotechnology has improved our daily life, but it also gives rise to potential risks to ecosystem. Hence, it is essential to further study on the translocation, destination and influence of nano-materials in ecosystem.There have been various reports different levels of effects of nano-materials on animals, human and microorganism, including beneficial effects and harmful effects. Compared with animal cells, the cell wall of plants makes it difficult for foreign body to enter plant cell. However, recent studies have shown that the pore diameter of cell wall, cell membrane, nuclear membrane and also the ion channel are with in the range of nanoscale. Little nanoparticles can enter into the cell through phagocytosis, active transport or directly entering the pore and play a role. When applied to the surface of leaves, nano-materials have the ability to enter plants through the pore. However, plants are the producer of nature, and also the origin of bioaccumulation. When nanoparticles accumulate through the food chain, it will result in toxic effects in advanced creature. Although plants play an important role in ecosystem, only limited studies have been carried out on the influence of nano-materials on the plant growth and development.Among different nano-materials, carbon-based nano-materials occupy increasingly significant role. But it is worth attention that whether the heavy use of carbon-based nano-materials has increased environmental risks. Graphene, a representor of carbon-based nano-materials, has been applied more and more widely. Hence, systematical research on the effects of graphene on plants will contribute to the research on the effects of nano-materials on environment. Among the various studies on toxicity, germination is an important criterion for determining the potential effects of environment on plants. Different plant seeds react differently to nanoparticles. There have been a few reports about the effects of graphene on seed germination rate. root extension, metabolism etc, and also about the uptake, bio-availabity and bioaccumulation. The study is conducted to investigate the influencing mechanism of carbon nanoparticles on high plants, through studying on the effects of graphene on rice germination, seedlings biomass, root morphology, antioxdase activity, lipid peroxidation. The final results are as follows:1. Graphene can certainly inhibite the germination of rice seeds, namely, delaying the germination rate of rice seeds. And, the delayed effects become more obvious with the increasing of graphene concentration. At certain concentrations, the effects of graphene on rice seeds are small. However, graphene has inhibited the growth of radicle and plumule. And the inhibitory effects strengthen with the increasing of graphene concentration.2. Graphene has certain effects on the morphogenesis of rice seedlings. After been treated by different concentrations of graphene for16d, the effects of5mg/L graphene on root length、stem length and root cap ratio are not obvious compared with control, with promoting effects on adventitious root number, root fresh weight, fresh weight of over ground part. The effects of50mg/L graphene on root length、adventitious root number, root fresh weight are not obvious, but significantly inhibite the stem length and the fresh weight of over ground part. Moreover,100mg/L graphene and200mg/L graphene obviously inhibite on the root length、stem length、adventitious number、root fresh weight、fresh weight of over ground part and root cap ratio. It indicates that the effects of graphene on the morphogenesis of rice seedlings show small or certain accelerating at lower concentration. Graphene certainly inhibite the morphogenesis of rice seedlings at higher concentration, and the inhibitory effects strengthen with the increasing of concentration.3. Graphene has certain effects on the physiological property of rice seedlings. After been treated by different concentrations of graphene for16d, the SOD activity, POD activity and CAT activity of5mg/1graphene treatment in rice tip are all lower than the control. The difference of MDA content is not obvious compared with control. And the chlorophyll content is obviously higher than control. With the increasing of graphene concentration, the activity of SOD, POD, CAT and MDA content in root tip are obviously higher than control. While, the chlorophyll content is obviously lower than control. It indicates that graphene is able to induce the antioxidant system in root to produce stress reaction, and changing the content of chlorophyll in leaves. The improvement of antioxidase enzyme activity can clear up excess oxygen when graphene concentration is lower. It won’t produce lipid peroxidation damage to the root tip cell, but obviously increasing the chlorophyll content in seedling leaves. With the increasing of graphene concentration, the improvement of antioxidase enzyme activity will produce peroxidation damage to the root tip cell and damage cell membrane structures. At the same time, chlorophyll content also decreases obviously, resulting in yellowing of leaves.