采用水杨酸（SA）、褪黑素(MT)、赤霉素(GA)3种辐射保护剂对⁶⁰Co-γ射线辐射处理后的小苍兰进行保护处理，以期减轻植物辐照后的损伤，降低辐照后种球的死亡率，增加其存活率和开花率，为花卉品种培育与改良提供行之有效的技术支持和数据参考。

以小苍兰为研究对象，用辐射剂量分别为55、65、75 Gy的⁶⁰Co-γ射线辐照处理小苍兰种球后，采用150、300、450 mg/L的SA和5、10、15 mg/L的MT和GA对其进行浸泡处理,以未使用保护剂的辐照组和清水处理组为对照，研究辐射保护剂对小苍兰生长发育指标及丙二醛含量（MDA）和超氧化物歧化酶（SOD）的影响。

辐射剂量为55 Gy时，150 mg/L SA处理组小苍兰发芽率和存活率分别达到了86.87%、90.00%，显著高于辐射对照组，株高比辐射对照组高144.63%，叶片数和叶片面积分别是辐射对照组的5.96、1.78倍，开花率达到最大值33.33%。当辐照剂量为65 Gy时，3种辐射保护剂的保护效果为低浓度小于高浓度,其中450 mg/L SA处理组小苍兰存活率达到79.67%，相对辐射对照组提高了91.68%,且15 mg/L MT处理组小苍兰小花朵数比辐射对照高出187.77%。在高剂量辐照（75 Gy）处理下，高浓度保护剂优于低浓度，其中450 mg/L SA处理组小苍兰存活率、株高、开花率分别较辐射对照组提高了122.23%、268.17%、500.60%，叶片数和叶片面积分别是辐射对照组的2.22倍、2.57倍。15 mg/L MT和GA处理可提高65、75 Gy剂量组小苍兰的小花朵数，相对于辐射对照组分别多7.83、5.68朵。并且使用3种不同浓度辐射保护剂后，均能显著降低辐射小苍兰MDA含量，延缓辐射后SOD 膜保护酶活性上升幅度，证明辐射保护剂能有效促进辐射损伤修复，减轻生理损伤。

辐照后使用SA、MT和GA浸泡处理能有效减缓小苍兰辐照损伤，起到辐射保护的作用。在55 Gy辐射剂量下，150 mg/L SA和15 mg/L MT保护效果较好，而在65和75 Gy辐射剂量下，450 mg/L SA、15 mg/L MT和15 mg/L GA保护效果较好。

Bulbs of ornamental plants have considerable economic value; however, seed degeneration is a major concern in several bulbous flower varieties due to its adverse effects on reproduction. Radiation mutagenesis bree?ding can help increase variation frequencies, enlarge variation ranges, and induce morphology?associated mutations, which may produce novel varieties within short time. However, plant survival is severely reduced due to physiological and genetic damage caused by ⁶⁰Co?γ radiation treatments, and the frequency of beneficial mutations is low and insufficient. We used salicylic acid (SA), melatonin (MT) and gibberellin (GA) in order to reduce radiation?induced damage and death rates and to increase survival and flowering rates in freesia bulbs after ⁶⁰Co?γ radiation treatments. The results may provide important technical information and reference values for cultivation and improvement of flower varieties.

Freesia （Freesia hybrida） bulbs were treated using ⁶⁰Co?γ radiation at dosages of 55, 65 or 75 Gy after soaking treatments with SA at concentrations of 150, 300 or 450 mg/L and MT and GA at 5, 10 or 15 mg/L. Irradiated bulbs not treated with protective agents and bulbs treated with water only were used as controls. Effects of radiation protection on growth and development were assessed by measuring growth indicators and content of malondialdehyde (MDA) and superoxide dismutase (SOD).

At a radiation dose of 55 Gy, germination and survival rates in freesia bulbs treated with 150 mg/L SA were 86.87% and 90.00%, respectively, and were significantly higher than those of the radiation control group; plant height of freesia was 144.63% larger than that of the radiation control, and the number of leaves and total leaf area were 5.96? and 1.78?fold higher, respectively, compared to the radiation control. Flowering rates showed a maximum at 33.33%. At a radiation dose of 65 Gy, the three tested agents produced protective effects in a dose?dependent manner. In the 450 mg/L SA treatment, the survival rate was 79.67%, which was 91.68% higher than that in the radiation control; the number of small flowers in plants treated with 15 mg/L MT was 187.77% higher than that in the radiation control. In the high?dose irradiation treatment (75 Gy), high concentrations of protective agents showed better effects than low concentrations. Survival rate, plant growth and flowering rate in freesia bulbs treated with 450 mg/L SA were 122.23%, 268.17% and 500.60% higher, respectively, compared to the radiation control, and the number of leaves and total leaf area were 2.22? and 2.57?fold higher, respectively, than in the radiation control. Treatments with 15 mg/L MT and GA produced higher numbers of small flowers in freesia bulbs irradiated at 65 and 75 Gy with 7.83 and 5.68 more flowers, respectively, compared to the radiation control. Moreover, radiation protectants at different concentrations can significantly reduce the levels of MDA in irradiated freesia plants and delay the increase in SOD membrane?protective enzyme activity after radiation, suggesting that radiation protection agents can effectively promote the repair of radiation damage and alleviate physiological damage.

Treatments with SA, MT and GA after irradiation can effectively mitigate radiation damage and may thus be important for radiation protection. Treatments with 150 mg/L SA and 15 mg/L MT showed better protective effects than that of other groups of protective agents after radiation at 55 Gy, whereas under radiation doses of 65 and 75 Gy, 450 mg/L SA, 15 mg/L MT and 15 mg/L GA showed most effective radiation protection.