Effects Of Experimental Defoliation On Resource Allocation Of Integrated Physiological Units In An Andromonoecy Camptotheca Acuminata

The reduction of leaves will reduce the amount of photosynthesis production, further reducing the amount of resources available to the plants, thus affecting the vegetative and/or reproductive performance of plants. C. acuminate, endemic species of China, of which various organs contains an alkaloid Camptothecin (CPT, have significant anti-tumor activity and unique anticancer mechanism), caught the attention of many people. Camptotheca acuminate (Nyssaceae) is a perennial woody plant distributed in the Yangtze River and Southwest provinces of China. At present, taxonomic studies, geographic distribution, pharmacology studies, reproductive biology, the introduction and cultivation and other aspects of Camptotheca acuminate has been carried out extensive research by the domestic and international scholars. Most studies concentrate on its medicinal value, the allocation of resources for gender expression and semi-autonomous integrated physiological unit (IPU) in C. acuminata inflorescence within the research is still relatively scarce.The C. acuminate inflorescence, which is composed of1-13(generally4/5)capitula, was born in the apex of annually-formed short shoot. Due to the nutritional status and the first flowering year, Capitulum number of C. acuminate individualsis different. Within the cyme of C. acuminata, the early capitulais composed of hermaphrodite flowers, with large capitulum in diameter and high fruit set; the late capitulum (begin to blossom after the primary capitulum open for about a week) sex expression tend to male, with small capitulum in diameter and low fruit set or no fruit. Usually the same level capitulum, in which all the flowers of same capitulum synchronous blossom and showed protandrous, almost blossom at the same time. Male and female function in the same capitulum has an isolation of time. The main issues we addressed are:(1) Under natural conditions, variation and influencing factors of capitulum numbers within Cymes of C. acuminate individuals in different flowering years.(2) Pollen limitations were tested by comparing fruit set and infructescence mass between natural pollination group and supplementary outcrossing pollen group.(3) we regard the annually-formed short shoot of C. acuminata as an IPU, three levels of defoliation treatments were applied:100%(high),50%(low) or0%(control) on IPU, and examined the resulting impact on vegetative traits (such as the numbers of leaves, maximum photosynthetic rate, etc.) and reproductive traits (male reproductive traits and female reproductive traits, reproductive success, secondary sexual characteristics and characters, etc.).The results are as follows:(1) First flowering plants usually have only one inflorescence, and after two or three years, secondary and tertiary inflorescence and even more will gradually produce; Typically, after about three years the state of reproductive physiology time C. acuminata begin to stabilize, and the number of capitulum within cyme becomes fixed. And during the first three years of flowering, Capitulum number within cyme has a strong correlation with the diameter and length of IPU.(2)After the supplement of out-crossing pollen, the fruit set and infructescence mass was not significantly increased, thus the pollen limitation was not found(3)After defoliation treatment, the reduction of the total amount of available resources produced different degrees of impact on the vegetative traits and reproductive traits. Meanwhile, due to the inherent inflorescence structure and flowering time sequence of cyme, making defoliation in different capitulum position has generated diversity, of which secondary and tertiary suffered larger impact than the tertiary capitulum position. After defoliation, there are no leaves produced within IPU, but photosynthetic capacity of the remaining leaves was enhanced. Surprisingly, pollen numbers, one of the male reproductive characteristics, showing different degrees of change reduced model at different positions of cyme, while female reproductive traits is always decreased.In conclusion, resource limitations and architectural effects together determine the resource allocation of integrated physiological units in an andromonoecy C. acuminate.