Analysis Of Salt-tolerant Characteristics And Primary Selection Of Its Salt-tolerant Variants From Tube Plants Of Triploid Populus Tomentosa

Populus tomentosa is one of the indigenous tree species which exhibits many excellent characteristics such as broad adaptability to environment, short growth period and high quality wood. But it can't grow normally when the concentrations of salt attain to 0.3% in soil. That was one of reasons why the distribution of P. tomentosa was confined. Based on the many excellent characteristics of P. tomentosa , selection of salt-tolerant variants was an important method to breed new clones with improved resistance to salt by somatic variation from culture in vitro oBased on the high differentiating rate of leaves and callus, the Salt-tolerant characteristics of shoots leaves and callus of tube plants from triploid P. tomentosa Carr. were analysed by one-stepped procedure. Growth of shoots leaves differentiating and inducing callus were inhibited in the media containing NaCl, but their sensitivities to NaCl were different. Sensitivity of leaf was stronger than the others, there's no differentiation in the media containing NaCl 0.4%, differentiating rate of leaves in the media containing NaCl 0.3% has obviously change, therefore the media of NaCl 0.3% was the suitable selection media for leaf differentiation. But sensitivities of plantlet and callus were not stronger than that of leaf, they can grow normally in the media of NaCl 0.4%, growth raised within the media of NaCl 0.4% and sharply declined beyond the range. On the base of analysing their salt-tolerant characteristics, NaCl 0.2% was thought as the initial concentration, increasing NaCl concentration step by step and more times selection in the salt and non-salt media, Salt-tolerant plants which can endure NaCl 0.35% and 0.4% from leaves differentiating and callus regenerating were obtained. The physiology and biochemistry indexes of the plants from leaf differentiating were measured, the result indicated proline and MDA contents were increasing with NaCl concentration increasing.Additionally, other leaves were irradiated by Y rays, The result indicated irradiation treatment has strongly effection on leaf differentiation. The differentiating rate raised with irradiation dose increasing within some range, whenirradiation dose was lOGy, differentiating rate was the highest, differentiating rate was 67.11% and was 1.5 times that of the control. Continuing to raise irradiation dose, increasing range of leaf differentiating rate increasingly declined, when irradiation dose was 30Gy, differentiating rate was lower than that of control, irradiation dose was 50 Gy, differentiating rate was 0. Plants from leaf differentiating by 20 Gy irradiation treatment were inoculated to the media of NaCl 0.3% and successively cultured three periods, then transferred to non -salt media for one period and once added to the media containing different concentration NaCl. The result indicated plant growth by irradiation treatment in salt stress was higher than the control and directly being added to salt , It showed irradiation can alleviate salt harm on plant . Irradiation can enhance salt- tolerant characteristics and benefit for selection of salt-tolerant variants.