The current research progress in China shows that the tree species of rhizobia that have been found are mainly trees of 11 genera in Papilionaceae,Elaeagnaceae and Mimosaceae,and the rhizobia are mainlyα-rhizobia,which come from multiple genera.Temperature,pH value,NaCl content and antibiotics all affect the growth of tree rhizobia;and different species of rhizobia have different stress resistance,which is related to their living environment.Rhizobium inoculation can promote plant height,biomass,root-to-shoot ratio,and root architecture of trees.We discussed and analyzed the development history and application status of rhizobia research,and prospected their future development directions.In the future,tree rhizobia will surely be used as a means of production to promote efficient agricultural production and sustainable agricultural systems.
Low-tempemture stress is a major abiotic stress influencing plant growth, economic yield and quality worldwide. Precise and reliable identification and test of plant cold resistance is a foundation for exploring low-temperature damages, cold resistance mechanism of plants, cultivating and innovating quality cold-re- sistant germplasm resources, which is rather important for woody plants because their perennial and large-sized characteristics. Generally, most researches on plant cold-resistant physiology focused on identification and utilization of cold resistance worldwide, and a few on test methods of cold resistance, but cold resistance mechanism has been less reported. Therefore, researches on methods of identifying and testing plant resistance have achieved considerable progress, accumulated much experience and formed characteristics gradually in terms of methodology. Current methods of identifying plant cold resistance include open field/outdoor culti- vation evaluation, cold and frost damage investigation, simulated cold weather, and mathematical model forecast. And the methods of testing plant cold resistance include growth condition test, frozen index investigation, electrolyte leakage, bioelectrical impedance mapping and so on. Synthesizing the methods of identifying and testing plant cold resistance should be a key matter in the present and future researches and application of plant cold resistance physiology, improvement and in- novation of the identification and test will be an important direction of the future researches. Identification and test of plant cold resistance based on genomies, meta- bonomics and proteomics should be the new trend of the researches on physiology and ecology of plant cold resistance.
Red sandalwood(Pterocarpus santalinus)is the most precious species of Pterocarpus,and the long maturity period of its heartwood is an important factor limiting its development.The 1-year-old plants of P.macarocarpus were chosen as the rootstocks to graft red sandalwood with single-bud scions of 1-year-old shoots in spring.The 5-month survival rate reached over 80%,and the grafted plants grew well.Moreover,the grafting significantly promoted the formation and development of the heartwood of red sandlawood.At 18^(th)month after grafting,compared with the seedling plants,the diameter of heartwood was increased by 82.8%and 29.6%,respectively,and the ratio of heartwood increased by 64.8%and 29.6%,respectively.The propagation technology had outstanding practical value and scientific significance,which has not been reported at home and abroad.
