Abstract: 【Objective】 The objective of study is to analyze the contents of different phytohormones at different developmental stages of a dwarf-multi-tiller rice mutant and its wild-type, and also compare the changes of morphological traits when treated by different plant growth substances. 【Method】 A T-DNA inserted dwarf-multi-tiller rice mutant (designed CA648) and its wild-type Zhonghua 11 (designed ZH11) were used as materials. HPLC was employed to analyze GA1, GA4, IAA, Z and ABA levels at different developmental stages (3rd leaf, 5th leaf, mid-tillering and booting stage), and compare the phytohormones content between CA648 and ZH11 in different organs (root, culm and leaf). In addition, endogenous IAA, Z and ZR were quantified at the booting stage in the different organs (root, stem, leaf and basal node) by using HPLC-MS/MS method, and the ratio of IAA to Z+ZR was used to compare between CA648 and ZH11. The changes of agronomic traits such as plant height and tiller numbers after the plants treated by spraying different plant growth substances (GA3, IAA, Z and paclobutrazol) were also examined.【Result】The trend of phytohormonal change between CA648 and ZH11 varied in different organs at different developmental stages. The content of GA1+4 in the culm and root of CA648 was higher than in ZH11, while there was no obvious difference in leaf at 3rd leaf stage, and the trend of GA1+4 content in culm (or stem) and root were raised but in leaf it was descended in ZH11 from 5th leaf to heading stage. However, a contrary trend was observed in CA648 for GA1+4 content in culm, root and leaf from 5th leaf to heading stage. IAA content showed no significant difference at 3rd leaf stage between CA648 and ZH11. A higher level of IAA in culm but a lower level in leaf sample of CA648 than ZH11 at the 5th leaf and mid-tillering stage were observed. At booting stage, the same part of root, stem or leaf had almost the same level of IAA, no matter the samples were from CA648 or ZH11. The level of Z was lower in CA648 than ZH11 in root or stem at 3rd leaf stage. At booting stage, CA648 had higher Z+ZR content in basal node or stem, but it had a lower level Z+ZR in leaf than that in ZH11. The ratio of IAA to Z+ZR in sample of leaf or stem from CA648 was greater than that of ZH11, but in sample of basal node or root had the contrary trend. ABA content in CA648 was higher at 3rd leaf and 5th leaf stages, but lower at booting stage than in ZH11. Results of spraying plant growth regulators showed that the plant height of CA648 is sensitive to exogenous GA3, IAA, Z or paclobutrazol but the multi-tiller characteristic were stable. In comparison with control (sprayed H2O), all treatments by application of exogenous GA3, IAA or Z could increase the plant height of CA648, and GA3 exhibited the highest sensitivity, followed by IAA and Z. But the plant height of CA648 and ZH11was decreased in case of paclobutrazol application. Although both CA648 and ZH11 plant height could be regulated by exogenous GA3 or paclobutrazol application, CA648 showed hypersensitive reactions to exogenous GA3. The plant height of CA648 could be rescued back to or even higher than ZH11 when 288 µmol•L-1 or higher level of GA3 was sprayed. It was different to plant height, the multi-tiller trait of CA648 was insensitive to exogenous plant growth substances, and it always produced more tillers than ZH11, being irrelevant to plant growth substance treatment. 【Conclusion】 The contents of GA1, GA4, IAA, Z, ZR and ratio of IAA to Z+ZR in CA648 are more beneficial than that of ZH11 to produce a dwarf-multi-tiller trait, therefore, the level of phytohormones contents and their ratio can reflect the physiological characteristics of CA648. Plant growth substances application caused different effects on plant height and tiller number. Spraying GA3, IAA, Z or paclobutrazol can change CA648’s height, while the multi-tiller trait is unaffected.

Key words: rice , phytohormone , dwarf-multi-tiller , mutant