Heavy Metal Cadmium Tolerance on the Growth Characteristics of Industrial Hemp (Cannabis sativa L.) in China

Abstract

Abstract.The effects of different concentrations of cadmium (Cd) on the growth physiological parameters of industrial hemp, including growth, the photosynthetic characteristics, the chlorophyll fluorescence and so on, were studied with hydroponic greenhouse experiments. The results showed that with the increase of Cd concentration, the levels of chlorophyll a, chlorophyll b and carotenoids in hemp leaves decreased, and the decreasing rates were in the following order: carotenoid> chlorophyll b>chlorophyll a. For the plants under Cd stress, net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) showed a downward tendency as the concentration of Cd increased, while intercellular CO 2 concentration (Ci) increased slowly. During the stress process, the maximum primary photochemical efficiency (Fv/Fm) and the photosynthetic electron transport rate (ETR) decreased. The actual quantum yield (Yield) and the photochemical quenching coefficient (qP) showed an apparent middle low point at 50 μmol/L, increased with increasing Cd concentration, and then decreased rapidly after the concentration reached 75 μmol/L. The non-photochemical quenching coefficient (NPQ) reached its maximum value at Cd level of 50 μmol/L. The Cd stress has significant impacts on the photosynthetic mechanism of industrial hemp. With a high concentration of Cd (>75 μmol/L), photosynthetic metabolism of hemp was inhibited and damaged. The Cd tolerance of hemp was related to the protection mechanism of chlorophyll a. Under Cd stress, there was a self-protection mechanism to reduce the impact of Cd stress on the photosynthesis in hemp via sacrificing the carotenoids to protect the chlorophyll in hemp leaves.

Assessment of cadmium tolerance and phytoextraction ability in young Populus deltoides L. and Populus × euramericana plants through morpho-anatomical and physiological responses to growth in cadmium enriched soil

“…Considering the significant increase in intercellular CO2 concentration in both poplar clones, but differential gs response following Cd exposure, our results suggest different mechanisms (stomatal and/or mesophyll impairments) are involved in Cd-induced reduction of photosynthetic activity in the studied poplars. Reduction of net photosynthetic rate due to mesophyll limitations has been observed in other woody (Salicaceae -Vassilev et al 2005) and herbaceous (Tang et al 2015) species exposed to Cd. However, the increase of intercellular CO2 levels observed in both clones (regardless of gs) suggests inhibition of Calvin cycle enzymes rather than PSII activity in the tested clones (Pajević et al 2009).…”

Effect of cadmium on young plants of Virola surinamensis

“…2E) and increase of NPQ (Fig. 2F) showed that the damage to PSII induced by a high Cd dose was not enough to cause the photoinactivation, with PSII being protected by an effective dissipation mechanism of heat to avoid the photoinhibition at the reaction centres (Li et al 2015; Tang et al 2015), these findings are corroborated by Ge et al (2015).…”

“…The effects of Cd stress on chlorophyll fluorescence parameters ( Fv/Fm , qP , ETR and NPQ ) (Fig. 2) may indicate an inhibition of the activity of PSII, resulting in changes in the photosynthetic rate of plants (Pajević et al 2009; Tang et al 2015). The reduction of Fv/Fm values (Fig.…”

Phycoremediation and photosynthetic toxicity assessment of lead by two freshwater microalgae Scenedesmus acutus and Chlorella pyrenoidosa

“…The higher YII values indicate strong PSII activity and higher energy conversion to photochemical products. Lower YII values indicate closed reaction center, low absorption and conversion (Yang et al, 2015). In our study, the increased YII values at lower concentration of Pb 2+ treatment could be correlated to the culture tolerance.…”