Irradiance stress responses of gas exchange and antioxidant enzyme contents in pariparoba [Pothomorphe umbellata (L.) Miq.] plants

Abstract

We evaluated the growth and development of the medicinal species Pothomorphe umbellata (L.) Miq. under different shade levels (full sun and 30, 50, and 70 % shade, marked as I 100 , I 70 , I 50 , and I 30 , respectively) and their effects on gas exchange and activities of antioxidant enzymes. Photosynthetically active radiation varied from 1 254 μmol m −2 s −1 at I 100 to 285 μmol m −2 s −1 at I 30 . Stomatal conductance, net photosynthetic rate, and relative chlorophyll (Chl) content were maximal in I 70 plants. Plants grown under I 100 produced leaves with lower Chl content and signs of chlorosis and necrosis. These symptoms indicated Chl degradation induced by the generation of reactive oxygen species. Stress related antioxidant enzyme activities (Mn-SOD, Fe-SOD, and Cu/Zn-SOD) were highest in I 100 plants, whereas catalase activity was the lowest. Hence P. umbellata is a shade species (sciophyte), a feature that should be considered in reforestation programs or in field plantings for production of medicinal constituents.

Shade level effects on yield and chemical composition of the leaf essential oil of Pothomorphe umbellata (L.) Miquel

“…These results corroborate those of Mattana et al (2006) for leaf and root biomass of P. umbellata plants, which yielded more when subjected to 30% shade. The present results are also confirmed by those of Marchese et al (2008), who analyzed the photosynthetic activity of pariparoba plants grown under different irradiance levels and noticed that higher CO 2 assimilation rate, as well as higher stomata conductance, occurred at PAR of 835.7 μmol m -2 s -1 (30% shade), indicating interrelation of factors.…”

“…The correlation between biomass production and essential oil was reported by Marchese and Figueira (2005), who wrote that the production of essential oil is associated with higher irradiance and higher photosynthetic rate, but high irradiance in esciophytes plants, as P. umbellate, usually cause chlorosis and necrosis with the photodegradaton of chromopigments, leading to a reduction of photosynthesis and biomass yield (Marchese et al, 2008). Analysis of P. umbellata essential oil evidenced that shade levels and season of harvesting did not alter its chemical composition as the same substances were present in all treatments, except that their concentration varied (Table 2).…”

“…Environmental factors, e.g. photoperiod, radiation and temperature have strong influence on plant development and the relation between biomass production and essential oil is related to higher radiation and photosynthetic rates of plants (Marchese and Figueira, 2005 (Mattana et al, 2006;Marchese et al, 2008).…”

Forage yield, rate of CO 2 assimilation, and quality of temperate annual forage species grown under artificial shading conditions

“…Photon energy is the only energy source used by plants, and the level of irradiance can affect their growth and development (MARCHESE et al, 2008). Thus, the growth rate of fodder is rapidly restricted due to the limited light energy required for photosynthetic processes.…”

Effects of hydric deficiency on gas exchange parameters and metabolism of Eucalyptus grandis clones

“…When plants are exposed to stressing environments (low temperatures, hydric deficiency, high intensity of light and others), the accumulation of ROS increase causing damages to cells due to the oxidation of constituents, especially at cell membrane (Asada, 1999;Broetto et al, 2002;Marchese et al, 2008). The enzymes that are involved in the ROS dismutation system are generally superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR).…”