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1.
Ying Yong Sheng Tai Xue Bao ; 35(3): 622-630, 2024 Mar 18.
Article in English | MEDLINE | ID: mdl-38646749

ABSTRACT

Soil nitrogen and phosphorus are two key elements limiting tree growth in subtropical areas. Understanding the regulation of soil microorganisms on nitrogen and phosphorus nutrition is beneficial to reveal maintenance mechanism of soil fertility in plantations. We analyzed the characteristics of soil nitrogen and phosphorus fractions, soil microbial community composition and function, and their relationship across three stands of two-layered Cunninghumia lanceolata + Phoebe bournei with different ages (4, 7 and 11 a) and the pure C. lanceolata plantation. The results showed that the contents of most soil phosphorus fractions increased with increasing two-layered stand age. The increase in active phosphorus fractions with increasing stand age was dominated by the inorganic phosphorus (9.9%-159.0%), while the stable phosphorus was dominated by the organic phosphorus (7.1%-328.4%). The content of soil inorganic and organic nitrogen also increased with increasing two-layered stand age, with NH4+-N and acid hydrolyzed ammonium N contents showing the strongest enhancement, by 152.9% and 80.2%, respectively. With the increase of stand age, the composition and functional groups of bacterial and fungal communities were significantly different, and the relative abundance of some dominant microbial genera (such as Acidothermus, Saitozyma and Mortierella) increased. The relative abundance of phosphorus solubilization and mineralization function genes, nitrogen nitrification function and aerobic ammonia oxidation function genes tended to increase. The functional taxa of fungi explained 48.9% variation of different phosphorus fractions. The conversion of pure plantations to two-layered mixed plantation affected soil phosphorus fractions transformation via changing the functional groups of saprophytes (litter saprophytes and soil saprophytes). Changes in fungal community composition explained 45.0% variation of different nitrogen fractions. Some key genera (e.g., Saitozyma and Mortierella) play a key role in promoting soil nitrogen transformation and accumulation. Therefore, the conversion of pure C. lanceolata plantation to two-layered C. lanceolata + P. bournei plantation was conducive to improving soil nitrogen and phosphorus availability. Bacteria and fungi played important roles in the transformation process of soil nitrogen and phosphorus forms, with greater contribution of soil fungi.


Subject(s)
Nitrogen , Phosphorus , Soil Microbiology , Soil , Phosphorus/analysis , Nitrogen/analysis , Nitrogen/metabolism , Soil/chemistry , Cunninghamia/growth & development , China , Bacteria/classification , Bacteria/growth & development , Bacteria/metabolism
2.
Yi Chuan Xue Bao ; 31(5): 495-501, 2004 May.
Article in Chinese | MEDLINE | ID: mdl-15478611

ABSTRACT

GH and IGF-1 may serve as negative feedback factors to regulate GH secretion from pituitary by binding to their respective receptors in hypothalamus and/or pituitary. In order to evaluate the line-specific developmental patterns of negative feedback regulation of GH secretion, Erhualian (EHL) and Large White (LW) pigs with significant difference in growth rate were employed in present study to investigate the developmental changes of GH receptor (GHR) mRNA and type-1 IGF receptor (IGF-1R) mRNA in hypothalamus and pituitary from birth till 180 days of age by relative quantitative RT-PCR. Pigs were sampled at birth, 3 , 20, 30, 90, 120 and 180 days of age respectively. Hypothalamic GHR mRNA was expressed according to an age-dependent manner, being low at birth, then increased steadily till day 120, followed by a decrease (P < 0.05) at the age of 180 days, suggesting that the sensitivity of hypothalamus to the GH negative feedback influence increase steadily during fast-growing period. LW boars expressed higher level of GHR mRNA than EHL boars (P < 0. 05) in hypothalamus. In pituitary, however, the GHR mRNA level was not significantly correlated with the breeds and age. The results suggested that GH might act mainly at the level of hypothalamus to regulate GH secretion. In contrast, the expression of IGF-1R mRNA exhibited line-specific developmental patterns in pituitary but not in hypothalamus. Hypothalamic expression of IGF-1R mRNA was abundant but did not show significant differences between ages, groups or lines. In pituitary, however, the IGF-1R mRNA expression was found to be high at birth both in EHL and LW pigs, subsequently declined till day 20, then followed by a slow rise reaching the second peak at the age of 90 days. At the age of 180 days, the pituitary IGF-1R mRNA level was higher in EHL pigs than that in LW pigs (P < 0.05), but the opposite was true at the age of 30 and 90 days. These results suggest that the site for receiving the feedback signal of IGF-1 is more likely in pituitary rather than in hypothalamus in the pig.


Subject(s)
Hypothalamus/metabolism , Pituitary Gland/metabolism , Receptor, IGF Type 1/genetics , Receptors, Somatotropin/genetics , Age Factors , Animals , Female , Gene Expression , RNA, Messenger/analysis , Swine
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