寄主植物芥蓝中磷元素与菜青虫生长之间的关系

Relationship between the Phosphorus Element in Host Plant Brassica alboglabra L. H. Bailey and the Growth of Pieris rapae(L)

为了探究菜青虫生长与寄主植物芥蓝（Brassica alboglabra L.H.Bailey）中磷元素之间的关系,本研究通过设置5个不同P浓度的营养液来栽培试验蔬菜芥蓝,每个浓度芥蓝放入10条1日龄试验菜青虫（Pieris rapae L.）以观察其生长变化,每24 h观察一次虫子的体长变化,试验周期为一周。观察菜青虫体内营养元素的组成以及与寄主植物跟营养液之间的关系,待虫子长到5日龄后,对整条虫子进行液氮处理并冻干机干燥48 h磨成粉末状,并收集虫蛹,进行统计。用钼酸铵-分光光度法测P元素,重铬酸钾氧化-分光光度法测C元素,研究结果表明：营养液、饲养菜青虫的芥蓝叶片与菜青虫之间有着一定的相关关系。随着营养液P浓度的降低,芥蓝叶片P含量也显著降低（p〈0.05）;不同芥蓝叶片含P量与C/P之间呈负相关;菜青虫体内P含量与芥兰叶片C/P之间同样呈负相关关系,与芥蓝叶片P含量和C/P之间关系呈现一致性;芥蓝叶片中C含量表现出较稳定趋势,由此可以看出,芥蓝叶片含P量与其C/P比之间的变化主要靠P元素起作用的,而且其含P量直接受营养液P浓度的影响。不同P浓度芥蓝叶片在7 d内对菜青虫的体长变化有显著的影响（p〈0.05）。随着P浓度的降低,每天菜青虫的体长变化也随之减慢;不同P浓度芥蓝叶片对菜青虫蛹重的变化有显著影响,随着P浓度的降低,蛹重也逐渐变轻（p〈0.05）说明芥蓝叶片含P量则直接影响菜青虫体内的含P量,菜青虫体内含P量则间接受营养液含P量的影响,且菜青虫会随着P浓度的降低而生长出现不同的差异性。这符合生长速率理论假说（The grow rate theory）和内稳态机制（Homeostasis）,而且也为昆虫在生态化学计量学方面的研究提供了新思路。

The study aimed to explore the relationship between the growth of Pieris rapae（L） and the phosphorus element in host plant Brassica alboglabra L. H. Bailey, In this study, 5 nutrient solutions with different phosphorus concentrations were set to culture test vegetables of Brassica alboglabra. Then 10 Pieris rapae（L） of 1 day old were put in solutions for each concentration of Brassica alboglabra to observe its growth. The changing of length in Pieris rapae（L） was observed on every 24 hours for a week. We also observed the composition of nutrient elements in Pieris rapae（L） and the relationship between the host plant and nutrient solution. When the Pieris rapae（L）growed for 5 days, a whole Pieris rapae（L） was treated with liquid nitrogen and ground to powder, and after drying48 hours, pupae were collected to make statistics. The phosphorus element was tested by the ammonius molybdate-spectrophometry and the carbon element was tested by using the potassius dichromate oxidation-spectr-ophometry. The result showed that there were certain relationships among nutrient solution, Brassica alboglabra L.H. Bailey and Pieris rapae（L）. With the reduce of the phosphorus concentrations of nutrient solution, the P contents of Brassica alboglabra L. H. Bailey reduced apparently, too（p〈0.05）. There was a negative correlation relationship between different P contents of Brassica alboglabra L. H. Bailey and its C/P. What＇s more, the result showed that there was a negative correlation relationship between P contents of Pieris rapa（L） and Carbon/phosphorus（C/P）,with consistence of Brassica alboglabra L. H. Bailey and its C/P. Further more, the carbon of Brassica alboglabra L. H. Bailey had a stable tendency. These results indicated that the change of P contents of Brassica alboglabra L.H. Bailey and its C/P was decided by the phosphorus element, and the P contents of Brassica alboglabra L. H.Bailey were affected by the P contents of nutrient solution directly. Different P contents of Brassica alboglabra L.H. Bailey affected the change of body length in Pieris rapae（L） obviously in a week（p〈0.05）. With the decrease of P contents of Brassica alboglabra L. H. Bailey, the change of Pieris rapa（L） length became slowly too. Different P contents of Brassica alboglabra L. H. Bailey affected the weight of pupae obviously（p〈0.05）. When the P contents of Brassica alboglabra L. H. Bailey reduced, the pupae became light gradually which indicated that the P contents of Brassica alboglabra L. H. Bailey affected the P contents of Pieris rapae（L） directly, and the P contents of Pieris rapae（L） were affected by the P contents of nutrient solution indirectly. In addition, with the reduce of P contents,Pieris rapae（L）, there would be some differences in their growth. It conformed to the grow rate theory（GRH） and Homeostasis, and might provide a new idea for the study of insects in ecological stoichiometry.