Effects Of UV-B Radiation On The Glandular Trichomes And Photosynthetic Characteristic Of Dendranthema Indicum Var. Aromaticum

Dendranthema indicum var. aromaticum was introduced from Shennongjia in Hubei Province and cultivated for many years in the garden nursery of College of Landscape Architecture, Northeast Forestry University. Selected three vary greatly individuals to breed three clones by the method of shoot cutting and referred to as S₁₄₀₁, S₁₄₀₇ and S₁₄₁₅.In this study, we preliminarily compares the three strains of plant form, leaf shape, the density of table surface morphology, leaf surface secretion and photochemical characteristics. Using ultraviolet UV-B on Dendranthema indicum S₁₄₀₁, S₁₄₀₇ for processing, the processing time was 1d,3d, 5d,7d, then we study the effect of ultraviolet radiation on the photosynthesis, the density of the epidermis and the surface of the leaves. Results show that:1. Large differences that exists in the three strains, were reflected in plant height, leaf shape, morphology and density of T-shape non-glandular hairs. Capitate glandular hairs have secretory function, which of S₁₄₀₁ and S₁₄₀₇ was distributed only on the lower epidermis, but S₁₄₁₅’s were mainly localized in the outer epidermis, with a few glandular hairs. Leaf surface exudates compounds are a group of complex compounds among which 93 were identified, including some of alkenes, camphor, alcohols and ketones. Among them, the content and variety of the alkenes is the largest.Light compensation point of three strains of Dendranthema indicum var. aromaticum have little difference. S₁₄₁₅’s light saturation point is the highest and it’s adaptation range is the widest, while adaptation range of S₁₄₀₁ is narrow. The S₁₄₀₇ net photosynthetic rate is highest, which indicated that the photosynthetic capacity of the strongest, the utilization efficiency of light is the highest. The fluorescence parameter difference between them, the initial fluorescence F0, S₁₄₀₇>S ₁₄₁₅>S ₁₄₀₁; potential quantum efficiency （Fv/Fm） no significant difference, maintained at about 0.82. With the increase in UV-B days of treatment, the net photosynthetic rate and intercellular CO₂ concentration of Dendranthema indicum var. aromaticum showed firstly increased and then decreased, while stomatal conductance and transpiration rate decreases and then increases. In the early days of treatment of UV-B radiation, F0 increased significantly. S₁₄₀₇ is particularly vulnerable and mean that this impact is compounded. Fv/Fm, Fv/F0 showed first increased and then decreased trend, that when subjected to a moderate UV-B stress, plants can make certain adaptation reaction, with treatment time prolonged, Fv/F0 and Fv/Fm values began to decline. Photochemical quenching （qP） decreased, Dendranthema indicum var. aromaticum scattered excess energy by improving the qN.3. With UV-B radiation, the content of chlorophyll a and chlorophyll b of Dendranthema indicum var. aromaticum presented the reducing trend, carotenoid content varied subtly. Under UV-B stress, RuBPCase carboxylase activity decreased, and with prolonged radiation showed a trend of the first lift.4. UV-B stress caused damage of glandular and non-glandular hairs or even fall off, resulting in significantly lower density. Leaf surface secretion of alpha pinene, the relative content of alpha olefin cubeb oil did not change obvious, while Juniper terpene and 1-caryophyllene Changes in volatility. Relative percentage content of camphor, alcohols and ketones compounds presented first increased and then decreased with the increase of treatment days. Their content reached largest in the 1d or 3d and 7d to a minimum.