不同质地土壤夏玉米生育后期光合特性比较研究

Photosynthetic Characteristics of Summer Maize ( Zea mays L.) during the Late Growth Stage in Different Soil Texture

在4种质地不同的土壤和2种施肥水平下,研究了玉米的光合特性。结果表明,黏壤土、壤土、砂质壤土和壤质黏土玉米生育后期光合速率(Pn)差异达显著或极显著水平,玉米生育后期各处理的光合参数的日变化存在明显差异,不同质地土壤玉米Pn、Ls 表现为黏壤土>壤土>壤质黏土>砂质壤土,Ci 表现为砂质壤土>壤质黏土>壤土>黏壤土,Gs 表现为质地黏重的土壤大于轻质土壤。蜡熟期各处理的Pn、Gs、Ls 明显小于乳熟期。施肥使各种质地土壤玉米Pn、Gs 和Ls 明显提高,Ci 降低,尤其砂壤玉米变化更为明显。不同处理玉米的叶面积动态和产量差异显著。

Light is one of the important factors affec ting development of corn and corn production (Zea mays L.), especially at silk stage later. Besides ecological factors, photosynthetic efficiency is aff ected by soil texture and mineral nutrition. Soil texture is one of the importa nt soil physical properties having effects on photosynthetic parameters by which maize growth is affected. Up to now, it is unclear how these parameters chang e and what their diversities are. The two-year pool-culture experiments with four kinds of soil textures (sand y loam, loam, clay loam and loamy clay) and two levels of fertilizations (with and without fertilizer) were conducted during 2000 and 2001 to study the yield response and its underlying photosynthetic mechanisms. The area of each pool wa s one square meter with six plants inside. Corn (Yedan 22) was planted on June 7 and harvested on September 17 in both years. Leaf area index and yield of maize varied greatly with different soil textures and fertilization levels (Table 2 and Fig.1). The order of the changes was cl ay loam > loam > loamy clay > sandy loam. Fertilization increased their values . Net photosynthetic rate (P n) under each soil texture was extremely dif ferent in the late growing stage (Table 3). Form silk to dough stage, the maxi mum value of P n occurred in clay loam, the minimum in sandy loam. Fertil ization enhanced the value of P n especially in dough stage and under sandy loam. Daily change of photosynthetic rates showed differences among soil textu re in both milk and dough stages (Fig.2).The highest value appeared under clay loam, the lowest under sandy loam. And the distinctions were prominent at noo n among soil texture. In addition, daily changes of intercellular CO 2 concen tration (C i) and stomatal limitation (L s) were also studied (Table 4 and Fig.3). Results showed that the value of C i was least at noon and t he value of L s was very high at that time. The values of C i under d iffere nt soil texture were sandy loam > loamy clay > loam > clay loam, while that of L s exhibited the opposite. Daily changes of stomatal conductance (G s) wer e single peak curves in silk stage and were double peak curves in dough stage, under different soil textures (Fig.4). With the growth of maize, stomatal con ductance decreased gradually. Fertilization increased stomata conductance, whi ch agreed with the high P n and the high corn yield.