Subjects: Biology >> Botany >> Applied botany submitted time 2023-07-13 Cooperative journals: 《广西植物》
Abstract： Nitrate is predominant in the karst soils. However, the temporal and spatial heterogeneity was observed for the nitrate content in the soils. Hence, the Morus alba seedlings grown in karst regions may suffer from low nitrogen stress. In order to provide a scientific management of inorganic nitrogen for M. alba seedlings grown in karst regions, the M. alba seedlings were used as the experimental materials in this study. The M. alba seedlings were grown hydroponically with a modified Hoagland solution. NaNO3, with a δ15N of 22.35‰, was employed as the sole nitrogen source at three concentrations (0.5, 2, and 8 mmol·L-1) in this study. The photosynthetic characteristics, dry weight, carbon content, nitrogen content and δ15N values of the leaves, stems and roots of the M. alba seedlings were measured in this study. The physiological response to different nitrogen supply levels was analyzed for M. alba seedlings. The relationship between internal nitrogen demand and external nitrogen supply of M. alba seedlings was estimated based on the stable nitrogen isotope fractionation values at the whole-plant scale. The carbon-nitrogen coupling relationship was studied based on the nitrogen accumulation amount and carbon accumulation amount in the whole plant. The results were as follows ： (1) When the nitrate concentrations ranged from 0.5 to 2 mmol·L-1, increasing nitrate concentrations significantly increased the chlorophyll content and net photosynthetic rate of the M. alba seedlings, which in turn significantly promoted the biomass accumulation. However, when the nitrate concentration exceeded 2 mmol·L-1, more nitrate supply (8 mmol·L-1) did not lead to a significant increase in the chlorophyll content, net photosynthetic rate and biomass. (2) Increasing the nitrate supply could promote the nitrogen assimilation in M. alba seedlings. The nitrogen accumulation amount in M. alba seedlings gradually increased with increasing nitrate supply. However, the carbon accumulation amount in M. alba seedlings did not change significantly at nitrate concentrations of 2 mmol·L-1 and 8 mmol·L-1; (3) The stable nitrogen isotope fractionation values of the nitrate assimilates in the whole M. alba seedlings reached the minimum value at 2 mmol·L-1 nitrate. Therefore, the inorganic nitrogen supply at the nitrate concentration of 2 mmol·L-1 is close to the internal nitrogen demand of M. alba seedlings, and the close balance between external nitrogen supply and internal nitrogen demand of the plants means an effective coordination of carbon and nitrogen metabolism in plants, thus achieving a simultaneous increase in carbon and nitrogen assimilates.
Subjects: Biology >> Botany >> Applied botany submitted time 2022-03-18 Cooperative journals: 《广西植物》
Abstract： To investigate the effects of HCO3- on the growth and physiological characteristics of plants under the stress of bicarbonate in karst environment. The growth, photosynthetic capacity, antioxidant enzyme activity, osmotic regulating substance content and cell membrane damage of Broussonetia papyrifera seedlings and those of Morus alba seedlings under three different concentrations of NaHCO3 (0,15，30 mmol·L-1, respectively) were examined in the present study. The results were as follows: (1) Under HCO3- stress, the growth and photosynthetic capacity of Broussonetia papyrifera and Morus alba seedlings were significantly inhibited, accompanying the physiological responses of leaf cells to antioxidant and osmotic stress were significant. (2) The inhibitory effect of HCO3- on the growth of Broussonetia papyrifera and Morus alba was concentration-dependent, and showed a significant difference among examined concentrations (P < 0.05). (3) The inhibitory effects of the growth, photosynthesis, antioxidant enzyme system and osmotic regulation system and the damage of plant cells under 30 mmol·L-1HCO3- treatment were significantly stronger than that of 15 mmol·L-1HCO3- treatment. (4) Under the same concentration of HCO3-, the growth, photosynthetic capacity, antioxidant enzyme activity, osmotic regulating substance content of Broussonetia papyrifera were significantly higher than those of Morus alba, and its leaf cell damage was significantly lower than that of Morus alba. The results mentioned above indicate that HCO3- inhibits the growth, photosynthesis and resistance physiology of Morus alba and Broussonetia papyrifera under bicarbonate stress, and the tolerance of Broussonetia papyrifera to bicarbonate stress is better than that of Morus alba, which means that Broussonetia papyrifera is more adaptable to the environment of bicarbonate stress. This study provides scientific support for the adaptation mechanism of Moraceae to karst environment.
Subjects: Biology >> Botany >> Applied botany submitted time 2021-07-20 Cooperative journals: 《广西植物》
Abstract： Bicarbonate (HCO3-) is the product of karst weathering of carbonate rocks, which profoundly affects the growth and development of plants and the ecological environment in karst areas. Previous studies mostly focused on the negative effects of HCO3- on plant growth and metabolism, such as inhibiting plant photosynthesis, reducing the activity of key enzymes in carbon and nitrogen metabolism, and damaging ion balance. Few people paid attention to its positive effects on plant growth and metabolism. Based on the results of previous studies, this paper reviewed the role of HCO3- in promoting plant growth and metabolism. Previous studies have shown that HCO3- is not only provides short-term carbon and water sources for plants under stress such as drought, but also promotes stomatal opening and restores photosynthesis. At the same time, it also promotes plant carbon and nitrogen metabolism by regulating the key enzyme activities of carbon and nitrogen metabolism, and participates in the regulation of complex physiological processes such as carbon assimilation and nitrogen reduction in plants. In addition, HCO3- can also change the distribution of glycolysis pathway and pentose phosphate pathway by affecting glucose metabolism disproportionation, so as to enhance the stress resistance of plants and obtain survival opportunities. These positive effects of HCO3- are not only make it a key factor to promote plant physiological metabolism, but also become a link connecting photosynthesis and karstification. Clarifying the positive effect of HCO3- on plant growth and development can provide a theoretical basis for maintaining the biodiversity and stability of karst ecosystem and optimizing the function of karst ecosystem.
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