| Lettuce is chosen as the experimental material of the study, and effects of application of seaweed extract and microelement fertilizers of Mn and/or Zn on growth, photosynthesis feature, enzyme activity of leaf, nutrient absorption and resistance are analyzed, to aim at providing instructional reference for reasonable application of seaweed extract and microelement fertilizers of Mn and/or Zn, and for reasonable way to apply seaweed extract. The main results as follow:(1) Comparing with treatment CK, applications of only seaweed extract, Mn or Zn all are showed that improviing seed sprouting, seed germination is increased 9.50 %, 17.00 % or 7.51 % respectively, germinative force is 112.90 %, 73.80 % or 69.50 % respectively, and germinative index is 9.60 %, 17.90 % or 7.50 %. But applications of seaweed extract and fertilizer of Mn or Zn are not significantly influence on seed , even restraining sprouting . During the early stages of lettuce growth, applying seaweed extract is showed to enhance significantly every index of growth. Using Zn fertilizer or Mn and Zn fertilizer is given the results of improvement of plant height and dry weight. During the whole stage of lettuce growth, applying seaweed extract enhances significantly growing of lettuce, and increases number of leaves, stem diameter, plant height, root length and dry weight of plants. Using Zn fertilizer or Mn and Zn fertilizer significantly enhances every index of growth potential of lettuce.(2)During exuberant growth period of lettuce, applying seaweed extract is studied to enhance significantly absorbing in nitrogen, phosphor and potassium, and transmitting from root to aerial part. And combinative applications of seaweed extract and microelement Mn or Zn are presented to have effects insignificantly; During later growth stage, with lettuces growing slower and slower and plants becoming old, using Zn fertilizer or Mn and Zn fertilizer significantly enhances absorbing and transmitting of nitrogen on the basis of applying seaweed extract, and improves absorbing in phosphor and potassium, but not transmitting them from root to aerial part. During exuberant growth period, there is a result of being restrained for absorbing of Mn and Zn in leaf by applying seaweed extract, the amount of Mn and Zn with only seaweed extract is presented to be 2.06~1.64 times higher than application of both seaweed extract and fertilizer of Mn or Zn. So the study gets the better result on applying respectively seaweed extract and Mn or Zn rather than on combinations. During later growth stage, the combinative application of seaweed extract and microelement Zn improves absorbing of Zn significantly, the amount of Zn in leaf is increased 23.95 % comparing with application of only seaweed extract.(3)During the stage of lettuce growth, applying Mn fertilizer increases 15.81~21.93 % of content of chlorophyll in leaf. In the condition of shortage of Mn in leaves, applying seaweed extract or Zn fertilizer is presented to increase chlorophyll content; neither is applying seaweed extract and Mn. Applying Mn fertilizer increases photosynthesis of lettuces, transpiration rate and stomatal conductance. On the basis, using seaweed extract effects more significantly.(4)In the condition of adversity stress, applying seaweed extract increases 10.79~66.13 % for SOD activity in enzymatic system of leaves, and enhances stress resistance of lettuces. Simultaneously, adding Zn fertilizer or Mn with seaweed extract has obviously effects on increasing 51.33~71.32 % of SOD activity.(5)Applying fertilizer way in which pouring a third of totals during the four-leaf period, then two thirds during the medium period of growth, and adding fertilizer generally obviously increase leave numbe, plant height, and dry weight by 25.08 %, 18.36 % and 23.59 % respectively, and absorbing of N, K, Ca and Mn is also been increased . Applying seaweed extract is showed to hamper absorbing in Zn, Cu and Mg.
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