銅、鋅與錳對兩品系葉用甘藷生長及養分吸收的影響

Abstract

金屬元素銅、鋅和錳為植物生長所必須之微量元素，然而，因污染造成環境中含量過高而影響植物的生長和養分吸收。在台灣，葉用甘藷生長快速，是一種普遍種植的食用蔬菜。本試驗的目的為探討在不同銅、鋅與錳濃度下，對葉用甘藷生長與養分吸收的影響。 本試驗在本校農場簡易溫室利用水耕栽培台農71號及桃園2號葉用甘藷。以 Johnson培養液的處理作為對照組 (代號 Control)，重金屬處理包括：二十倍銅 (代號Cu20X )、一百倍銅 (代號Cu100X)、二十倍鋅 (代號Zn20X )、一百倍鋅 (代號Zn100X)、二十倍錳 (代號Mn20X)及一百倍錳 (代號Mn100X)。試驗設計採逢機完全區集排列，每處理四重複。分別在種植後二個星期及四個星期採收，植體分為上位葉、上位莖、下位葉、下位莖、根部，在 65℃ 下烘乾後，稱其乾重，經磨碎分解進行化學分析，測定項目為氮、磷、鉀、鈣、鎂、鐵、錳、銅、鋅等營養元素。 試驗結果顯示，經過四個星期的處理，台農71號較桃園2號生長狀況佳，然而，不論台農71號或是桃園2號皆以 Mn20X 的生長情形最佳，其氮、磷、鉀、鈣、鎂、鐵吸收量也是各處理中最高。養液中添加的重金屬濃度增加時，植體地上部的濃度也隨之增加，台農71號生長二個星期的最高處理銅、鋅、錳濃度分別為 39 mg/kg、2232 mg/kg、930 mg/kg，生長四個星期的最高處理銅、鋅、錳濃度分別為 60 mg mg/kg、829 mg/kg、1790 mg/kg，桃園2號生長二個星期的最高處理銅、鋅、錳濃度分別為 41 mg/kg、2203 mg/kg、1298 mg/kg，生長四個星期的最高處理銅、鋅、錳濃度分別為 68 mg/kg、761 mg/kg、3170 mg/kg。銅、鋅、錳最高吸收量的處理分別為 Cu20X、Zn20X、Mn100X。結果顯示，二個星期與四個星期的銅最高濃度 Cu100X 處理有顯著增加，銅最高吸收量 Cu20X，銅處理已有毒害情形產生。鋅的最高濃度 Zn100X 處理在第二次採收期較第一次採收期低，而所有重金屬處理中，也是鋅毒害最嚴重，最高吸收量是 Zn20X。錳的最高濃度 Mn100X 處理則有高達二倍的明顯變化，Mn100X處理也是吸收量較高者，由此可知，Johnson 養液配方中的錳對此二品系葉用甘藷是不足的。

Copper (Cu), zinc (Zn), and manganese (Mn) are necessary trace elements for plants, however, high concentrations owing to pollution in the soil influence the growth and nutrient uptake of the plants. High content of latex is one of the characteristics of leaf sweet potato. In Taiwan, leaf sweet potato (Ipomoea batatas (L.) Lam) is a kind of popular edible vegetables. The objective of this study was to investigate that the effect of different concentrations of Cu, Zn, and Mn on the growth and nutrient uptake of leaf sweet potato. The experiment was conducted in the greenhouse. The cultivated cultivars of leaf sweet potatoes were Tainung 71 and Taoyuan 2. Johnson nutrient solution was used as check (Control). The treated metal concentrations included 20-fold and 100-flod for Cu, Zn, and Mn, respectively. All treatments were arranged in a randomized complete block design with four replications. The plants were harvested after treating for two and four weeks, respectively. The harvested plants were separated into upper leaf, upper stem, lower leaf, lower stem and root then dried at 65℃ to constant weight. The concentrations of nitrogen (N), phosphorus (P), potassium (P), calcium (Ca), magnesium (Mg), iron (Fe), Mn, Cu, and Zn were analyzed. The result shows that the dry weight yield of Tainung 71 was higher than that of Taoyuan 2 after treating for four weeks. The dry weights of both cultivates of Mn20X treatment were the highest among all treatments. The N, P, K, Ca, Mg, and Fe uptake of Mn20X treatment were also the highest among all treatments. The concentrations of heavy metals in the shoot increased with the increasing metal concentrations of the nutrient solution. For Tainung 71, the highest concentrations of Cu, Zn, and Mn were 39, 2232, and 930 mg/kg, respectively, after being treated for two weeks and those for growing for four weeks were 60, 829, and 1790 mg/kg, respectively. For Taoyuan 2, the highest concentration of Cu, Zn, and Mn were 41, 2203, and 1298 mg/kg, respectively, after growing for two weeks, and those for growing for four weeks were 68, 761, and 3170 mg/kg, respectively. The Cu concentration of the shoot of leaf sweet potato of Cu100X treatment increased with the growing period. Under this circumstances, the elevated Cu concentration in the nutrient solution resulted in the toxicity to the leaf sweet potato. The Zn concentration of shoot of the leaf sweet potato of Zn100X treatment also increased with the growing period and toxic symptoms appeared. Mn100X treatment resulted in the highest concentration of Mn in the shoot of leaf sweet potato. However, the growth of leaf sweet potato was little affected by the high Mn treatment which indicated that the Mn concentration in Johnson’s solution is too low for the growth of the two cultivars of leaf potato.