Agronomy and Horticulture Department

 

Date of this Version

Fall 9-9-2013

Citation

Proctor, C.A. 2013. Biology and control of common purslane (Portulaca oleracea L.). Ph.D. Diss., Univ. Nebraska, Lincoln.

Comments

A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Agronomy, Under the Supervision of Professor Zachary J. Reicher. Lincoln, Nebraska: September, 2013

Copyright (c) 2013 Christopher A. Proctor

Abstract

Common purslane (Portulaca oleracea L.) is a summer annual with wide geographic and environmental distribution. Purslane is typically regarded as a weed in North America, but it is consumed as a vegetable in many parts of the world. One of the characteristics that make purslane difficult to control as a weed is its ability to vegetatively reproduce. Severed sections of purslane stem containing a node will produce adventitious roots from the cut end of the stem. Isoxaben and simazine were the only two effective preemergence herbicides for controlling purslane in our studies when applied at maximum or one-half maximum label rates. Of the 25 postemergence herbicides evaluated, fluroxypyr, triclopyr, dicamba, and metsulfuron-methyl were the most effective for controlling purslane. Purslane’s ability to adapt to a broad range of environmental conditions is due, in large part, to its unique photosynthetic metabolism. Under well-watered conditions, purslane utilizes C4 photosynthetic metabolism. However, purslane will shift to a CAM-like photosynthetic metabolism under droughty conditions, with nocturnal acid accumulation in the leaves and reduced CO2 uptake. Phosphoenolpyruvate carboxylase (PEPC) catalyzes the initial step in photosynthetic fixation of atmospheric CO2 in C4 and CAM plants. Regulation of PEPC is primarily via phosphorylation by PEPC kinase (PEPCK). For well-watered purslane, PEPC and PEPCK transcript abundance are indicative of C4 metabolism, but in water-stressed purslane, PEPCK transcripts accumulate at night suggesting a shift in the phosphorylation pattern of PEPC to CAM-like metabolism. By understanding purslane’s unique photosynthetic metabolism, we can gain insight into how it effectively adapts to water limiting environments.