Growth, reproduction, and photosynthesis of ragweed parthenium (Parthenium hysterophorus)

Abstract

Growth and reproductive potential with respect to season and photosynthetic gas exchange behavior under elevated (short-term) CO2 at varying temperature, relative humidity (RH), and irradiance levels were investigated in ragweed parthenium (also known as carrot grass and congress grass), a noxious weed in India. Lower values of biomass, relative growth rate, net assimilation rate, crop growth rate, leaf area duration, leaf area index, and numbers of flowers and seeds in winter compared with summer stands showed that ragweed parthenium is greatly suppressed by low temperatures during winter. This was due to constrained vegetative growth, seedling emergence, and seed to flower ratio. The species showed maximum photosynthetic response to temperature at 25 to 35 C, and the net photosynthetic rate was reduced considerably at a low temperature (7 C). These temperatures approximately corresponded to the normal temperatures experienced by summer (25–35 C) and winter (7 C) stands of ragweed parthenium. Elevated CO2 enhanced leaf net photosynthetic efficiency, maximum photosynthetic rate, and water use efficiency (WUE) but decreased the light compensation point for net photosynthesis, stomatal conductance, and transpiration rate. The interactive effects of elevated CO2 and temperature resulted in a decrease in light-limited and light-saturated net photosynthetic rates and WUE. The interactive effects also reduced an elevated CO2-induced decrease in light compensation point relative to elevated CO2 alone. Stomatal conductance was insensitive to photosynthetic photon flux but was greatly influenced by RH. Leaves of the species may show increasing rates of net photosynthesis with a rise in CO2 and temperature. However, excessive increase in transpiration with temperature, especially at 47 C (noon temperature during summer in the plains of northern India), appears to be disadvantageous for the leaves when conservation of water is of prime importance.

The stimulating impact of elevated temperatures on growth and productivity of <i>Parthenium hysterophorus</i> L.

“…According to Long et al (2008), warm temperature at the time of Parthenium seed production enables the seed once shed to persist in the soil for more than three years, whereas cool temperature permit survival for only 1 -3 years. Toh et al (2011) reported that increased temperature enhances growth of Parthenium, enlarges canopy size and structure and accelerates population growth rate because of the shortened life cycle, supported by Entz &Fowler (1991) in wheat and Pandey et al (2003) in Parthenium. Singh & Singh (2010) reported the extensive coverage of vacant cultivated land during summer by Parthenium.…”

Control of Ragweed Parthenium (Parthenium hysterophorus) and Associated Weeds

“…A native of northeast Mexico, ragweed parthenium is one of the world's worst weeds and causes serious health problems in humans and animals (Kadhane et al 1992;Pandey et al 2003). It has become widespread in North and South America and many parts of Africa, Asia, and Australia, but is most serious in India and Australia.…”

The Status of Parthenium Hysterophorus and its Potential Management

“…Limited earlier investigations suggest that parthenium has both Cr and Ca phoios],nthetic pathway with leaves on top having Cr mesophyll with non-Kranz leaf analomy and l€av€s at the middle and base having C4 mesophyll with Kranz anatomy (Rajendrudu and Rama Das 1990), However, Pandey et al (2003) nol€d that photos),nthetic chamctedstics of parthenium leaf mosdy r€lated with Ca $?e pathway. They also found that slomaLal conductancc ofpa henium is insensitive to photosynihetic photon llux but is geatly influenced by relative humidity.…”