Effects of CeCl_3 and LaCl_3 on callus and root induction and the physical response of tobacco tissue culture

La3＋ and Ce3＋ have positive effects on plant growth and production. Although it is well known that rare earth elements promote cell growth. The biological effects of La^（3＋） and Ce^（3＋） on callus, shoot and root induction in tobacco are still unclear. The relationships among callus induction, rooting, enzyme activities and stomatal characteristics in tobacco are unknown. The objectives of this study were to identify the relationships between the induction of calluses, shoots, roots, stomata and enzyme activities. The induction percentages of calluses, buds, roots were recorded at 5,10,15, 20 and 25 days after La^（3＋） and Ce^（3＋） treatments. Peroxidase isoenzyme activity was determined by electrophoresis. The characteristics of the stomata were observed under an optical microscope. Our results show that low concentrations of Ce^（3＋）（〈15 mg/L） result in increases in the induction percentages of calluses,buds and roots, but La^（3＋）（〉5 mg/L） inhibits the induction of calluses, buds and roots. There are more peroxidase isoenzyme bands in Ce^（3＋） treatments than in La^（3＋） treatments. This is consistent with the induction percentages of calluses,buds and roots in Ce^（3＋） and La^（3＋） treatments. High enzyme activities may promote the induction of calluses, buds and roots. The stomata area and stomata number of leaves are significantly different between La^（3＋） treatments and Ce^（3＋） treatments. La^（3＋） improves the stomata area and number. Based on these results, we speculate that La^（3＋） may promote the development of the photosynthetic system. Ce^（3＋）may promote tobacco growth and rooting by improving enzyme activities.

Recent advances in regenerative biomaterials

Nowadays,biomaterials have evolved from the inert supports or functional substitutes to the bioactive materials able to trigger or promote the regenerative potential of tissues.The interdisciplinary progress has broadened the definition of‘biomaterials’,and a typical new insight is the concept of tissue induction biomaterials.The term‘regenerative biomaterials’and thus the contents of this article are relevant to yet beyond tissue induction biomaterials.This review summarizes the recent progress of medical materials including metals,ceramics,hydrogels,other polymers and bio-derived materials.As the application aspects are concerned,this article introduces regenerative biomaterials for bone and cartilage regeneration,cardiovascular repair,3D bioprinting,wound healing and medical cosmetology.Cell-biomaterial interactions are highlighted.Since the global pandemic of coronavirus disease 2019,the review particularly mentions biomaterials for public health emergency.In the last section,perspectives are suggested:(i)creation of new materials is the source of innovation;(ii)modification of existing materials is an effective strategy for performance improvement;(iii)biomaterial degradation and tissue regeneration are required to be harmonious with each other;(iv)host responses can significantly influence the clinical outcomes;(v)the long-term outcomes should be paid more attention to;(vi)the noninvasive approaches for monitoring in vivo dynamic evolution are required to be developed;(vii)public health emergencies call for more research and development of biomaterials;and(viii)clinical translation needs to be pushed forward in a full-chain way.In the future,more new insights are expected to be shed into the brilliant field-regenerative biomaterials.