Abstract
A field experiment was conducted using a 3 × 3 orthogonal regression design to explore the growth promotion of one-year-old Yunnan pine seedlings (Pinus yunnanensis Franch.) in response to foliar application of IAA (indole-3-acetic acid) at rates of 0, 200 and 400 mg·L−1 and IBA (indole-3-butyric acid) at rates of 0, 200 and 400 mg·L−1 in order to promote the growth during the seedlings’ early stage. The experiment was conducted at the Lufeng Village Forest Farm of Yiliang County in Kunming, Yunnan, China. The results showed that IAA and IBA were effective in growth promotion of Yunnan pine seedlings. The response of both growth increment and biomass accumulation to the concentration of IAA and IBA can be modeled using a bivariate surface response, and each growth index had a peak value. Growth indexes increased with the increase of the dosage of photohormones before reaching a peak value, and then decreased. The different growth indexes had various responses to the concentrations and ratio of IAA and IBA. The foliar application of IAA in combination with IBA showed the largest improvement on the biomass of the needles, followed by stems and roots. The higher ratio of IAA promoted stem diameter growth, root system development and biomass accumulation in the needles, while a higher ratio of IBA contributed to height growth and biomass accumulation in the stem. Based on the auxin effect equations on the different growth indexes and surface response, the optimum concentrations and the (IAA:IBA) ratios can be obtained. The optimum concentrations of IAA and IBA were 167 and 186, 310 and 217, 193 and 159, 191 and 221, and 206 and 186 mg·L−1, with corresponding ratios of 1:1.11, 1:0.70, 1:0.82, 1:1.15 and 1:0.90, respectively, at the maximum seedling height and collar diameter growth as well as biomass accumulation at the root, stem and needle. The above growth indexes were 22.00%, 79.80%, 48.65%, 82.20% and 107.00% higher than the control treatment.
Highlights
Yunnan pine (Pinus yunnanensis Franch.), an evergreen arbor of genus Pinus and subgenera Pinus in the Pinaceae family, is 52 m tall and 1 m in diameter, with a brown-gray colored bark, longitudinally fissured, with 10–30 cm needles in bunches of 3
In order to determine whether indoleacetic acid (IAA) and indolebutyric acid (IBA) could promote Yunnan pine seedling growth, one-year-old seedlings were treated with solutions of different concentrations of IAA in combination with IBA
From the analysis we found that the optimum concentration of IAA and IBA with foliar spray for Yunnan pine seedlings and their ratios, the theoretical maximum yield, and the related parameters can be obtained
Summary
Yunnan pine (Pinus yunnanensis Franch.), an evergreen arbor of genus Pinus and subgenera Pinus (of the hard pines, Diploxylon) in the Pinaceae family, is 52 m tall and 1 m in diameter, with a brown-gray colored bark, longitudinally fissured, with 10–30 cm needles in bunches of 3 (rarely 2) It is a common and commercially valuable species in southwestern China, occurring at elevations of. Pollination occurs April-May and seed maturity in October of the following year [1,3] This species plays a crucial role in regional economic development and ecological environment construction [3]. Research has implicated a role for IAA and IBA in promotion of seedling growth and root cutting formation in Yunnan pine. We first confirmed that IAA and IBA can promote seedling growth and we obtained the optimal concentrations and their ratios in their application for the acceleration of Yunnan pine seedling growth
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