Cuticular Waxes On Leaves Of Morus Alba And Its Relationship With Gas Exchange And Water Index

Plant surface is covered with a layer of hydrophobic cuticular wax, which is composed of a variety of lipophilic compounds with special microcrystal structure As the isolation barrier of the plant and the external environment, cuticular wax plays an important physiological and ecological functions, including limiting water transpiration, controlling gas exchange, shielding air pollutants, preventing ultraviolet radiation, protecting plants against pathogenic microbes infection As the direct contact surface of plants and environment, cuticular wax is sensitive to environment changes Its crystal structure effectively regulates plant response to environment, and plays an indispensable role in the process of plant growth and development Mulberry (Morus alba) is an important economic tree, which has important significance in purifying atmosphere, windbreak and sand fixation, soil and water conservation, maintaining ecological balance, and as silkworm feed and other medicinal and fodder values The mulberry is widely planted in china and is rich in species resources Therefore, studies on the relationship between mulberry leaf cuticular wax characteristic and leaf photosynthesis and leaf water loss have important theoretic roles in evaluating adaptability of mulberry germ-plasma resources in ChongqingThis study was conducted in Chongqing Sericulture Science Research Institute of Mulberry (Dongyang, Beibei) In total 52 mulberry varieties were analyzed for leaf water characteristics and chlorophyll index Among the 52 varieties, seven cultivars with different origins, A new Seto (Japan), Hu Mulberry 32 (Zhejiang), Tongxiangqing (Zhejiang), KanWa (Sri Lanka), Junyou 5(Zhejiang), Shaanxi Sweet Mulberry (Shaanxi) and Yu Mulberry 101 (Chongqing), were analyzed for wax morphology, leaf cuticular wax content, in vitro mulberry leaf moisture retention capacity (MRC), gas exchange parameters, and their relationships The main results were as follows:1. Results from 52 mulberry varieties showed that leaf MRC, chlorophyll index and the relative water content differed among varieties Among all varieties, the MRC was the highest in Bei 1 (76.12%) and lowest in Zhong Mulberry 5801 (35.44%); the chlorophyll index was the highest in Shiping Mulberry (49.45) and the lowest in Baipi Mulberry (34.23) Relative water content was the highest in Qingpi Hu Mulberry (94.41%) and the lowest in Longzhao Mulberry (78.34%)2. Mulberry leaf had dense epidermal wax layer, diffusely distributed in the entire leaf surface The leaf wax crystal in adaxial surface looked like "cap", which spread around from a central hump There existed less leaf wax crystal on abaxial surface and no cap structure was observed The stomatal density and stomatal index significantly differed among seven cultivars Yu Mulberry 101 had the biggest stomatal density while Tongxiangqing had the lowest The stomatal index was the highest in JunYou 5 and the lowest in A new Seto3.The amounts of total cuticular wax and wax compositions differed among varieties The wax amount in A new Seto was the highest and the lowest in Tongxiangqing and Hu Mulberry 32 Leaf cuticular wax was mainly composed of alkanes, alcohols, esters, acids, a small amount of aldehydes and ketones, and unknown wax components The alkanes accounted for 58% - 30% and alcohol accounted for 34%- 243% in total cuticular wax No aldehyde was detected in A new Seto, Yu Mulberry 101, Hu Mulberry 32 and Shaanxi sweet mulberry No ketone was detected in Tongxiangqing4.Leaf photosynthetic rate, stomatal conductance and transpiration rate in Yu Mulberry 101, Hu Mulberry 32 and Kanwa were significantly higher than other varieties Leaf intercellular CO2 concentrations in Tongxiangqing and New Ichinos were significantly lower than other varieties Leaf MRC also differed among varieties Five hours after sampling, the MRC maintained at 44%-65% Tongxiangqing and Hu Mulberry 32 had lower MRC The leaf relative water content and water vapor pressure difference were the highest in Shaanxi sweet Mulberry Leaf relative content was the lowest in Junyou 5 The vapor pressure was the lowest in Hu Mulberry 32 The leaf weight ratio was the highest in KanWa and the lowest in A new Seto and Yu Mulberry 1015. Mulberry leaf wax amount was positively correlated with leaf vapor pressure and MRC, negatively correlated with specific leaf weight, and not related with the relative water content The increase of wax amount benefited leaf moisture retention capacity Furthermore, the total cuticular wax amount was negatively correlated with leaf photosynthetic rate, stomatal conductance and transpiration rate, indicating that wax deposition on leaf surface prevented leaf gas exchange performance...