糖和氮对山楂组织培养新梢生根的影响

采用敞口山楂组培新梢研究糖和无机氮源对不定根形成的影响,含有高水平蔗糖的培养基比低水平蔗糖的培养基新梢生根率高。新梢对糖的这种反应与糖代谢和物理渗透都有关,用甘露醇作为渗透代替剂在低浓度蔗糖存在下无作用,当蔗糖浓度达到一定程度时(86.64mmol·1~(-1))能影响新梢的生根率。在培养基中分别加入NO_3~(-)-N或NH_4~(+)-N作为唯一氮源,或是在MS培养基中加入NO_3~-/NH_4~+比率为标准的混合氮源,在测试范围(0～120mmol·1~(-1))内均降低新梢的生根率,三者对生根的抑制作用大小顺序依次为NH_4~+>NO_3~(-)-NH_4~(+)-N>NO_3~(-)-N.NO_3~-/NH_4~+的比率影响生根。NO_3~-/NH_4~+比率与生根之间呈直线正相关。糖/氮比值高有利于生根。插穗中碳、氮的绝对量及碳/氮比率可作为山楂新梢生根的指标。

Effect of Sucrose and Nitrogen in Adventitious Root Formation on Hawthron Shoots in Vitro

Cultured shoots of hawthron (Crataegus pinnatifide Bunge var. NE. Br) cv. 'Changkou' adult trees were used to determined the effects of sucrose and inorganic nitrogen on adventitious root formation in vitro. Rooting percentages of shoots were increased in the medium containing higher sucrose concentration (116. 86mmol·1~(-1). This response to sucrose was mainly related to the metabolism of sucrose and little to its osmotic properties since the use of mannitol as osmotic substitutes did not reproduce the effect on rooting in the condition of lower sucrose concentration(58.43mmol·1~(-1)but did in 86. 64rnmol·1~(-1) sucrose concentration. The rooting percentages decreased when the shoots cultured in the media either with nitrate (NO_3~-), ammonium (NH_4~+) solely, nitrate-ammonium (NO_3~(-)-NH_4~+)or the ratio of theMS salt formulae(0～120mmol·1~(-1)). This inhibitory effect in descending order was shown as NH_4~+,NH_4~+-NO_3~-,and NO_3~-. The NO_3~-/NH_4~+ ratio was positively related with shoot rooting percentage ,the greatest rate of root initiation oecured on shoots grown in medium with a high sucrose to nitrogen concentration ratio. It was suggested that the content of carbohydrate and nitrogen and its ratio may be an index for the hawthron shoot rooting.