Effects of chlorocholine chloride and prohexadione-Ca on rhizome growth and lateral bud production in Iris germanica L.

Abstract

ABSTRACTIris germanica L. is a popular perennial flower worldwide, but its use is limited in China due to an inadequate availability of propagules. To accelerate rhizome growth and lateral bud production using plant growth retardants (PGRs), chlorocholine chloride (CCC; at 1,500 or 3,000 mg l−1) or prohexadione-Ca (at 700 or 1,500 mg l−1) were applied to uniform plants of I. germanica. Time-course measurements of changes in morphogenesis, carbohydrate metabolism, total soluble protein (TSP) concentrations, and endogenous phytohormone concentrations in rhizomes were conducted to test the efficacy of CCC or prohexadione-Ca for increasing rhizome growth and lateral bud production. The results showed that both PGRs increased the fresh weights of rhizomes at 2, 4, and 6 weeks after treatment (WAT). Overall, 700 mg l−1 prohexadione-Ca was most effective at promoting the formation of lateral buds which increased by 183.5% at 12 WAT relative to untreated control plants. Concentrations of sucrose and starch in PGR-treated rhizomes increased at 2, 4, and 6 WAT, while a decline was observed by 12 WAT. TSP concentrations increased during rhizome enlargement, then decreased during lateral bud germination after prohexadione-Ca treatment. In general, concentrations of endogenous phytohormones, such as gibberellins, indole-3-acetic acid, jasmonic acid, and zeatin riboside, decreased significantly in rhizomes at 4 WAT, then increased at 12 WAT. Our study indicated that prohexadione-Ca promoted rhizome growth and the accumulation of sucrose and starch before summer dormancy, then significantly accelerated the production of lateral buds.