Responses Of Quality Development Of Carrot To Soil Temperature And Moisture

Carrot is commonly known as "Little Ginseng", which is planted more than 2,000 years. It is the biennial vegetable, the cultivated area is expended in northwestern China day by day. In this paper, leaf length and number, root length and diameter, fresh and dry weight of aerial and underground part, leaf chlorophyll, malondialdehyde, soluble protein, soluble sugar, proline content and SOD, POD, APX activity, and photosynthetic characteristics are researched on different soil temperature and moisture under different growing stages,β-carotene, soluble solid, vitamin C, dietary fiber and size of xylem is researched on root harvest time, disussion of carrot growth, yield and quality formation and physiological and biochemical characteristics under different soil temperature and water stress. The results are as following:1.Mulching transparent film and black film could significantly improve soil temper-ature, daily mean soil temperature could increase 4.34℃and 3.33℃compared with CK in vegetative period.2. Growth of T3 (covered with transparent film,20th April seeded) and T4 (covered with black film,20th April seeded) on Aerial and underground parts are significantly higher compared with T2 (nothing covered,20th April seeded), and the growth rate of T3 is higher than T4. Growth rate of T1 (nothing covered,5th April seeded) is lowest compared with other treatment. Content of vitamin C is not difference among soil temprature treatment, size of xylem of T1 is the smallest compared with other treatment.content of B-carotene, soluble solids and hemicellulose is significantly higher than other treatments while covering with transparent membrane, qualities of carrot are increased.3. With the increase of soil temperature, content of MDA and soluble protein firstly decreased and then increased; soluble sugar content increased firstly and then decreased; proline content rises sharply with the increase of soil temperature; SOD, POD activity showed increased4. Growth of carrot is limited under water stress, the inhibition of severe stress treatment is most obvious compared with the control. Water stress led to change the qualities of carrot, size of xylem, soluble solids, cellulose and hemicellulose when the extent of water stress increased, but content of B-carotene, vitamin C is showed to drop, edible value was decresed.5. MDA content in leaves of carrot showed "decrease-increase-decrease" trend under different water stress when stressing time rises, and the membrane integrity has been undermined. Some physiological indicators (soluble sugar, soluble protein and proline), antioxidant enzymes (SOD, POD, APX) activity showed gradually increased as the stressing time rises, the soluble sugar, soluble protein and antioxidant activity increased quickly when soil moisture content reached 65%, which is significantly different among other treatments. The effort of photosynthesis of leaf played an increasingly visible role as stressing time rises, which is compatible with the chlorophyll content, content of chlorophyll decreasing also caused photosynthetic rates and photosynthetic products decreased.