Effect of Prolonged Photoperiod on Light-Dependent Photosynthetic Reactions in Cannabis

Abstract

Industrial hemp is a fast-growing, short-day plant, characterized by high biomass yields and low demands for cultivation. To manipulate growth, hemp is usually cultivated under prolonged photoperiods or continuous light that could cause photooxidative damage and adjustments of photosynthetic reactions. To determine the extent of changes in photosynthetic response caused by prolonged light exposure, we employed chlorophyll a fluorescence measurements accompanied with level of lipid peroxidation (TBARS) and FT-IR spectroscopy on two Cannabis cultivars. Plants were grown under white (W) and purple (P) light at different photoperiods (16/8, 20/4, and 24/0). Our results showed diverse photosynthetic reactions induced by the different light type and by the duration of light exposure in two cultivars. The most beneficial condition was the 16/8 photoperiod, regardless of the light type since it brought the most efficient physiological response and the lowest TBARS contents suggesting the lowest level of thylakoid membrane damage. These findings indicate that different efficient adaptation strategies were employed based on the type of light and the duration of photoperiod. White light, at both photoperiods, caused higher dissipation of excess light causing reduced pressure on PSI. Efficient dissipation of excess energy and formation of cyclic electron transport around PSI suggests that P20/4 initiated an efficient repair system. The P24/0 maintained functional electron transport between two photosystems suggesting a positive effect on the photosynthetic reaction despite the damage to thylakoid membranes.

Analyzing the Effects of Urban Photopollution on Photosynthetic Efficiency of Certain Trees through Chlorophyll Fluorescence OJIP Transient

“…Thus, the electron-transport capacity of PSII is reduced [59]. These results are similar to earlier studies on grass [60], cannabis [24] and fresh-water plants [27].…”

“…Study of the physiological mechanisms by which plants adapt to artificial light at night will help to select the species suitable for urban plantations and, consequently, to determine the success of urban plantations. Indeed, few previous studies were conducted in the natural environment, and most of the earlier findings on artificial light at night (ALAN) were mainly focused on plant ecosystem sustainability, while the studies showing the effects of ALAN on plant physiological processes were reported in very small numbers [24][25][26][27]. Trees growing under street-light conditions experience an extremely heterogeneous environment; therefore, the use of traditional analytical approaches in the early detection of stress would be expensive and time-consuming [28].…”

Comparative Analysis of Primary Photosynthetic Reactions Assessed by OJIP Kinetics in Three Brassica Crops after Drought and Recovery

“…The fully recovered φ R0 and δ R0 to the control values in white cabbage corroborated the increase in the electron flow rate at the PSI acceptor side (negative G band). Such results suggested the formation of functional adaptations as a response to drought in white cabbage [77,84,85].…”

“…A positive G band indicated a decrease in the PSII acceptors pool, accompanied by reduced electron transport and a subsequent reduction in the PSI reduction rate [75]. On the other hand, the negative G band seen in white cabbage was suggested to be a compensatory mechanism developed by plants exposed to inadequate and stressful conditions [37,77]. In such conditions, the number of available NADP + molecules increased, which, in turn, increased the activity of PSI [37,75].…”

Effect of Light Fluctuations on Growth Rate of Thalassiosira Sp.

“…adjust to changes in photoperiod. The adaptation strategy used by an organism to carry out photosynthesis depends on the type of light and the length of the photoperiod (Gajdošik et al, 2022). Short photoperiods can reduce the time available for photosynthesis, while long photoperiods provide more time for that process.…”