鎘與百日草木質部轉輸細胞的誘導

Abstract

百日草（Zinnia elegans）經鎘處理後，根部是第一個受到毒害的器官，其生長受到抑制，變黑且潰爛；同時鎘也會造成植株矮化、新葉黃化，且葉組織易老化的現象。鎘濃度在30μM以上時，植株生長會明顯的受到抑制。 百日草莖部（S3）木質部導管的數目經過不同濃度的鎘處理後，有起伏的變化。低濃度時（10μM）導管數量稍微減少，但之後隨著鎘濃度的上升而增加。到達60μM時，為最大值。但當鎘濃度過高時（100μM），維管束導管的數量反而下降。 鎘處理後的百日草植株，在莖部的木質部中，有轉輸細胞的產生，位於導管間薄壁細胞的位置。在根以及葉組織的木質部中，則沒有此種現象產生。在10μM低濃度的鎘處理下，木質部並沒有明顯的轉輸細胞產生。然而在30μM的鎘處理下，植株維管束內導管接觸的薄壁細胞則開始有細胞壁向內凹的情況。60μM鎘處理時，導管周邊的薄壁細胞壁內凹的情形更加明顯。但鎘濃度到達100μM時，薄壁細胞壁內凹的程度反而下降。 其他的金屬鋅、汞、鉛、銅處理百日草植株兩星期，在TEM下觀察這幾種金屬與百日草莖部S3木質部轉輸細胞誘導的情形。在硫酸鋅100μM、氯化汞100μM和硝酸鉛100μM處理的植株中，木質部皆有轉輸細胞的產生，其接鄰導管的細胞壁有向內凹的情形。但硫酸銅處理的植株，其莖部木質部的薄壁細胞，無細胞壁內凹的情形，細胞內容物少，無轉輸細胞的產生。 植物為了對抗重金屬逆境，因此產生了許多不同的同功酵素，無論是酸性磷酸酵素、超氧歧化酵素或是過氧化氫酵素，在不同濃度的鎘處理下，皆造成改變；葉蛋白質的總表現亦有所不同，尤其是60、100μM鎘濃度的處理下，更明顯的多了一種蛋白質的表現。

The growth of plant is inhibited obviously, when plant is exposed to cadmium above 30 μM. The symptoms of cadmium-treated Zinnia elegans are retardation of root and shoot; chlorosis of young leaves; early senescence of old leaves. The quantity of vessel elements in S3 xylem changes when Z. elegans is exposed to different concentration of cadmium. The numbers of vessel elements in S3 xylem decreases under low cadmium concentration. The numbers of vessel elements are more and more as the increase of cadmium concentration. However, if the cadmium concentration is too high, the quantity of vessel elements decreases (100 μM). Cadmium-induced xylem transfer cells are only found in xylem of stems, not in roots and leaves. They are located at parenchyma between vessel elements. The cell wall facing vessel elements of transfer cell has ingrowth. This kind of xylem transfer cells are not found in control plant. Under low cadmium concentration (10 μM), no transfer cell in xylem of stem is found. The cell wall of parenchyma ingrown, when the concentration of cadmium is up to 30 μM. The cell wall ingrowth of transfer cells is more obvious in plants exposed to 60 μM for two weeks. The degree of transfer cell ingrowth decreases as plant exposed to 100 μM. Similar induction of transfer cells are also found in xylem of plants exposed to 100 μM ZnSO4, 100 μM Pb(NO3)2 and 100 μM HgCl2 for two weeks. However, transfer cells do not be found in the plant exposed to 50 and 100 μM CuSO4. In order to resistant metal stress, plants may produce many different kinds of isozymes. The isozyme patterns of superoxide dismutase, peroxidase and acid phosphatase in leaves are altered by the duration of cadmium treatment. The expression of total protein in leaves is different in various concentration of cadmium, especially under 60 and 100 μM.