EFFECTS OF ROOT TEMPERATURE ON THE PHYSIOLOGICAL METABOLOLISM OF MUSKMELON(CUCUMMIS MELO L.)ZENG

Abstract

利用水氣耕栽植，控制溫室洋香瓜生長於15℃、25℃、35℃三種不同液溫 ，以探討對植株生長及代謝之影響。結果獲知，溫室洋香瓜在15℃之低根 溫處理下，其根部組織生長，較25℃及35℃根溫處理緩慢。顯示在15℃根 溫時，會改變正常之生理代謝而遲緩其生長。本實驗結果獲知，根部組織 中交替呼吸途逕活性，隨著根溫之降低而增加；而細胞色素呼吸途逕活性 變化則呈相反之趨勢。此結果顯示，低溫可能會降低組織中能量產生之效 率。根部組織中可溶性糖類含量，也會隨根溫降低而明顯地增加，其中以 蔗糖含量差異最為顯著，此結果則有利於進行「溢能效應」，促進交替呼 途逕呼吸，以彌補細胞色素途逕呼吸的不足。SS活性在15℃根溫處理下， 有明顯高於25℃及35℃處理；acid invertase活性則反之，以15℃根溫處 理時最低。此結果則顯示，在低根溫下，組織中分配於生長用之蔗糖減少 ，因而減緩根之生長。在15℃低根溫處理下，地上部之生長也有明顯減緩 現象。且地上部葉片組織之光合成率、暗呼吸速率、及Rubisco活性均隨 著根溫之降低而有顯著之降低，此結果可知，於低根溫處理之植株葉片組 織，同化作用亦較弱，而生長代謝較為低緩。在15℃根溫時，葉片中蔗糖 含量則明顯減少，而六碳糖則有明顯增加之現象。SPS、及acid invert- ase活性，則與蔗糖含量變化相似，在15℃低根溫下皆顯著低於25℃及35 ℃。然而其SS活性則以在15℃時有顯著之增高。此外，在15℃低根溫下， 葉片組織中有明顯累積大量澱粉。由葉片中蔗糖含量與其相關酵素活性分 析結果，除了可反應出，低根溫處理植株之葉片，其同化物質（蔗糖∕澱 粉）分配，傾向於澱粉之累積外。此一現象，亦可能是由於低根溫造成植 株根部生長遲緩，降低養分（蔗糖）之需求，因而促進組織中澱粉之累積 ，而澱粉大量之累積結果則間接地造成光合成作用的抑制. (A)The root growth rate ,leaf area ,total dry weight and fresh weight were decreasing with the root temperature decreasing, esp- ecially under 15℃ cold roottemperature stress. The results indi- cated that cold root temperature（15℃）was unfavor to growth.(B) Root under 15℃ medium temperature increased the souble sugars content such as sucrose, fructose, and glucose .There are no indi- cates significant differences between 25℃and 35℃treatment, exc- epting sucrose.The starch content,and SPS activity of root showed no significant differences among 15℃,25℃ and 35℃.These results indicated, the SPS did not play an important role on the tion of sucrose of the roots in muskmelon. But the activity of acid invertase under 15℃ is lower than others.The result indic- ated that the sucrose that partitioning to growth reduced. The cytochrome respiratory activity was decreased with root tempera- ture decreasing, however the alternative respiratory activity was increased.(C) The photosynthetic rate and Rubisco activity in the leaves under 15℃ root temperature were lower than others. The sucrose content in the leaves of muskmelon increased with root temperature decreasing. The behavior of SPS activity was similar to sucrose, but the starch accumulation was to the contrary. The result indicated that the source strength of leaves at 15℃ root temperature was lower than 25℃ and 35℃.In general，it showed the the growth of root in muskmelon under 15 ℃ root temperature was reduced.It caused to reduce the absorption of water and ions,then slowdown the growth of leaves.Besides, the retardation of roots reduced the sink strength of roots and reduced the export of suc- rose via decreasing photosynthesis capacity in the leaves.