Abstract
Temperature is one of the critical factors affecting rice growth and yield production. This study investigated the effects of rhizosphere temperature at the tillering stage on the growth, physiological parameters and gas exchange attributes of two rice cultivars, i.e., the super rice cultivar Yuxiangyouzhan and the non-super rice cultivar Xiangyaxiangzhan, under hydroponic conditions. Three rhizosphere temperature treatments, i.e., a low-rhizosphere-temperature treatment (LT, nutrient solution at 17.5 ± 1.5 °C), an ambient-temperature treatment (AT, nutrient solution at 27.5 ± 1.5 °C), and a high-rhizosphere-temperature treatment (HT, nutrient solution at 37.5 ± 1.5 °C), were applied in this study. The results showed significant differences in most of the rice growth and physiological and gas exchange parameters as a result of cultivar and rhizosphere temperature as well as their interaction. In addition, the marked reduction in total dry weight was positively correlated with a notable reduction in plant morphological parameters, such as the fresh and dry weight of the leaves and stem sheaths, and changes in gas exchange parameters. Moreover, antioxidant reactions were active in response to high and low rhizosphere temperatures, which varied in different plant tissues. These results suggested that the super and non-super rice were sensitive to high and low rhizosphere temperatures, respectively.
Highlights
Rice is one of the main food crops worldwide and plays an important role in maintaining food security in China[1,2]
The interaction of cultivar and temperature resulted in a significant effect on agronomic traits, SOD activity, POD activity, CAT activity, MDA content, proline content, whereas SPAD values, leaf area, leaf fresh weight, leaf fresh weight per area, root dry weight, stem sheath dry weight, leaf dry weight per area, SOD activity in the roots, MDA activity in the stems and proline content in the roots were not affected (Table 1)
This study showed that high temperature resulted in a significant increase in total fresh weight and leaf fresh weight for super rice, while no effect was observed in any organ fresh weight for non-super rice (Table 3), which was in accordance with a report stating that the fresh weight and chlorophyll decreased significantly under high-temperature conditions a LT AT HT aaabbc www.nature.com/scientificreports
Summary
Rice is one of the main food crops worldwide and plays an important role in maintaining food security in China[1,2]. Rice yields are significantly reduced by extreme temperatures[17,18] Grain quality, such as the head rice yield and grain width, can decrease under low- or high-temperature conditions, while chalkiness can increase[11,12]. Www.nature.com/scientificreports high temperatures can lead to reductions in photosynthesis, respiration, and physiological parameters, as well as RuBP carboxylase activity[23]. High or low temperature during the day or at night in the air or in the soil as well as high- or low-temperature irrigated water for rice plants could result in different growth responses in rice plants. Two rice cultivars, i.e., a super rice (Yuxiangyouzhan) and a non-super rice (Xiangyaxiangzhan) cultivar, were grown under three rhizosphere temperatures levels, i.e., low temperature (LT, 17.5 ± 1.5 °C), ambient temperature (AT, 28 ± 1.0 °C) and high temperature (HT, 38.5 ± 1.5 °C), for the purposes of evaluating the influence of rhizosphere temperature on the growth and physiological response of super and non-super rice varieties and investigating the correlations between the investigated parameters under different rhizosphere temperatures for super rice and non-super rice
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