Albino Plant And Higher Endogenous Reactive Oxygen Species Toxicity

Pure albino plant cannot survive in wild due to them inability of photosynthesis. In addition to the grafted albino plants,variegated mutant plants(partly albino) can live in forest understorey or in house circumstance. Compared with their normal green counterparts,these plants(grafted albino plants or variegated mutant plants) are less vigor i.e. retarded growth,smaller size,susceptible to pathogen and shorter life.Face these weak traits,people always contribute them to their inability(grafted albino plants) or low efficient(variegated mutant plants) of photosynthesis which lead to the shortage of carbohydrate or other nutrients. But this seemingly convinced explains cannot illustrate the phenomina below:1):variegated plants prefer light-reduced environment such as the forest understorey or house circumstance to live though their photosynthetic area of leaves shrinked contrasting with their normal counterparts which live in the strong light environment.2) published literatures suggest low efficient photosynthetic plants have a longer lifespan in nature,generally;but the low C-acquiring capacity of variegated mutant plants are easier senescent contrasting to their normal counterparts3)previous studies demonstrate the external supply of sugar or other nutrition can promote the growth rate and biomass production of albino plant in callus level,but thesesupplementary measures cannot make them reach the same size of their green counterparts. Elevation the atomosphere CO₂ concentration also has similar function in planta.Combination of these puzzling problems above and the facts below, we postulated these weak traits of albino plant may associated with their abnormal ROS metabolism such as antioxidant deficient or endogenous ROS overproduction or both:Firstly,many symptoms of albino plants are similar to the antioxidant loss plants such as the SOD or APX or ascorbate or a-tocopherol mutant plants.Secondly, the high turnover rate of the components of the thylakoids in defective chloroplast of albino cells will creat massive ROS which similar to the green leaves in their senescent stage. We used Hibotan-nishiki cactus(variegated mutant cactus) as our experiment materials and compared the ROS metabolism and sugar-related parameters of the albino tissue and green tissue in the mother ball(old stage) and the daugter ball(young stage) which growing on them. In one stage(mother ball or daughter ball):(1) the O^*₂^- production rate and the SOD activity of the albino tissues are slightly lower than their adjacent green tissues;(2) the H₂O₂ accumulation and themain scavenging enzymes(CAT and APX) activity of the albino tissues are greatly higher than their adjacent green tissues;(3) the content of the main nonenzymatic antioxidants such as the ascorbate and glutathione et al. of the albino tissues are greatly higher than their adjacent green tissues;(4) the DPPH radical scavenging ability of the 50% ethanol extracts of the albino tissues are significant higher than their adjacent green tissues;(5) the ratio of the ASC/DHA and the NADPH/NADP of the albino tissues(more oxidized) is significant lower than their adjacent green tissues; but the ratio of the GSH/GSSG of the albino tissues is significant higher (more reduced);(6) the content of the chlorophyll and carotenoid pigment of the albino tissues are very low(less than 1/10) contrasting to their adjacent green tissues,and this result are also confirmed by the light-spectroscopy observation of the handcut slice;(7) the content of the soluble sugar and starch of albino tissues are about halffold of the adjacent green tissues;(8) the content of the free amino acid of albino tissues are substantially higher than the adjacent green tissues;(9) if based on per unit lipid,the lipid peroxidation (MDA) of the albino tissues are markedlysevere than their adjacent green tissues.Based on above results,we can draw some preliminary conclusions:1 the sugar shortage phenominon donot exist in albino tissues at least when they are grafted on the green stocks;2 the low but detected level of photosynthetic pigments of albino tissues suggest the albino tissues are in a sink state and at the same time imply the albino cell can synthesis photosynthetic pigment but cannot be accumulated;3 the albino cells are in a low or moderate oxidative stress state though under control,contrasting with the green tissues;4 the ' abnormal' high level of H₂O₂ accumulation suggest the contribution of the non-SOD pathway may be a dominant pathway;5 the higher activity of the enzymatic or nonenzymatic antioxidant suggest the albino cell is not an antioxidant loss mutant;6 the oxidative stress state of the albino tissues in the young and old stage suggest this phenomonon only concern with albino phenominon.Combined the published data and our work,we have two major findings below:Firstly: a noval production pathway for higher endogenous reactive oxygen species due to the defective organelle existence was found:this is an entirely new model(differ to the antioxidant deficiency or external ROS supply) to study the ROS damage and toxic to plants;Secondly: we offer a new insight to explain the premature senescence and other weak traits of albino plants based on their higher endogenous ROS toxicity more than inability of photosynthesis.