Abstract
Increased ultraviolet-B (UV-B) due to global change can affect plant development and metabolism. Quinoa tolerates extreme conditions including high UV levels. However, the physiological mechanisms behind its abiotic stress tolerance are unclear, especially those related to UV-B. We previously demonstrated that 9.12 kJ m−2 d−1 may induce UV-B-specific signaling while 18.24 kJ m−2 d−1 promotes a UV-B-independent response. Here, we explored the effects of these UV-B doses on hormonal regulation linked to plant morphology and defense among diverse varieties. Changes in fluorescence parameters of photosystem II, flavonoids and hormones (indoleacetic acid (IAA), jasmonic acid (JA), abscisic acid (ABA) and salicylic acid (SA)) were surveyed under controlled conditions. Here, we showed that the sensitivity to short acute UV-B doses in varieties from different habitats is influenced by their parental lines and breeding time. UV-B sensitivity does not necessarily correlate with quinoa’s geographical distribution. The role of flavonoids in the UV-B response seems to be different depending on varieties. Moreover, we found that the extent of changes in JA and SA correlate with UV-B tolerance, while the increase of ABA was mainly related to UV-B stress.
Highlights
Light is an essential source of energy for photosynthesis, and functions as a signal source about the environment, and regulates diverse morphological, physiological and developmental processes in plants
Real showed a gradual and significant decrease of ΦPSII with the increase of UV-B irradiation dosage; a similar pattern was followed by Salcedo INIA but a significant decline was only observed in plants exposed to 18.24 kJ m−2 UV-B in comparison with the control (Figure 1a)
Titicaca showed a steep decline of ΦPSII only when plants were exposed to 18.24 kJ m−2 UV-B, while Blanca experienced this decline even at half the maximum UV-B dose (9.12 kJ m−2 ) (Figure 1a)
Summary
Light is an essential source of energy for photosynthesis, and functions as a signal source about the environment, and regulates diverse morphological, physiological and developmental processes in plants. Radiation belongs to a small fraction of the sunlight spectrum ranging from 280 to 315 nm. This part of the spectrum represents only 1.5% of the light reaching the surface of the Earth, it can have multiple impacts on the life systems due to its high energy [3]. Previous studies have shown that high doses of UV-B can induce massive production of reactive oxygen species (ROS), which stimulates the production of hormones (i.e., jasmonic acid (JA) and salicylic acid (SA)) and triggers a general defense response [7,8]. Low and moderate doses of UV-B have been shown to stimulate photomorphogenic responses, which are often hormone-dependent (i.e., auxin (IAA)) linked to the UV-B RESISTANCE
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