The cuttings of Populus przewalskii Maximowicz were exposed to three different watering regimes (100, 50, and 25% of the field capacity) in a greenhouse to characterize the morphological, ...physiological, and biochemical basis of drought tolerance in woody plants. Two contrasting populations of P. przewalskii were used in our study, which were from the wet and dry climate regions in western China, respectively. The results showed that there were significant differences in responses to three different watering regimes in both populations tested; drought not only significantly affected dry mass accumulation and partitioning but also significantly decreased chlorophyll pigment contents and accumulated free proline and total amino acids. On the other hand, drought also significantly increased the levels of abscisic acid, hydrogen peroxide, and superoxide radical as secondary messengers to induce the entire set of antioxidative systems including the increase of reduced ascorbic acid (ASA) content and the activities of superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase, and glutathione reductase (GR). Moreover, there were different responses to drought stress between the two contrasting populations of P. przewalskii. Compared to the wet climate population, the dry climate population showed lower dry matter accumulation and partitioned more biomass to root systems, and accumulated more free proline and total amino acids for osmotic adjustment. The dry climate population also showed more efficient antioxidant systems with higher content of ASA and higher activities of ascorbate peroxidase and GR than the wet climate population.
Investigating the responses of trees to the heterogeneous distribution of nutrients in soil and simultaneous presence of neighboring roots could strengthen the understanding of an influential ...mechanism on tree growth and provide a scientific basis for forest management. Here, we conducted two split-pot experiments to investigate the effects of nutrient heterogeneity and intraspecific competition on the fine root morphology and nutrient capture of Picea asperata. The results showed that P. asperata efficiently captured nutrients by increasing the specific root length (SRL) and specific root area (SRA) of first-and second-order roots and decreasing the tissue density of first-order roots to avoid competition for resources and space with neighboring roots. The nutrient heterogeneity and addition of fertilization did not affect the fine root morphology, but enhanced the P and K concentrations in the fine roots in the absence of a competitor. On the interaction between nutrient heterogeneity and competition, competition decreased the SRL and SRA but enhanced the capture of K under heterogeneous soil compared with under homogeneous soil. Additionally, the P concentration, but not the K concentration, was linearly correlated to root morphology in heterogeneous soil, even when competition was present. The results suggested that root morphological features were only stimulated when the soil nutrients were insufficient for plant growth and the nutrients accumulations by root were mainly affected by the soil nutrients more than the root morphology.
AIM: This study aimed at predicting how sub-alpine coniferous ecosystems respond to global changes in the Eastern Tibetan Plateau by understanding soil microbial communities and activities, as well ...as variation in the quality and quantity of soil organic matter. METHODS: An experiment was conducted to examine soil microbial communities and their related soil processes in rhizospheric soil of two coniferous species that were exposed to two levels of temperature (unwarmed and infrared heater warming) and two levels of nitrogen (unfertilized and 25 g N m⁻² a⁻¹) from April 2007. RESULTS: Four-year night warming alone slightly affected the phospholipid fatty acid contents of the microbial community. However, the combination of nitrogen addition and soil warming significantly affected soil microbial composition while reducing the biomass of major microbial groups and the activities of most enzymes, especially in Abies faxoniana plots. The combination of warming and nitrogen addition increased soil labile C and N pools in Picea asperata plots and was beneficial for soil recalcitrant C, as well as for labile and total C and N pools in A. faxoniana plots. CONCLUSION: Results indicated that future warming will slightly affect soil microbial communities and their related soil processes. However, warming combined with high nitrogen deposition will significantly constrain soil microbial biomass and enzyme activities, consequently increasing soil C and N pools in sub-alpine coniferous forests of this region.
Previous studies about the effects of experimental warming on tree species have focused primarily on response of morphology and physiology in leaf and biomass allocation in the growing season, and a ...few studies considered the importance of roots. Based on the available evidence, it is unclear whether photosynthesis rate is enhanced by night warming in late autumn an issue that deserves further investigation. Thus, we exposed two coniferous species, Picea asperata and Abies faxoniana, to night warming continued throughout the year to investigate morphological and physiological responses of roots and leaves in the autumn. The results showed that night warming caused significant increases in net influxes of NH4+ and NO3− in P. asperata seedlings corresponding well with net H+ efflux and net influx of O2. Meanwhile, night warming had a positive effect on foliar gas exchange such as net photosynthesis rate, apparent quantum efficiency, dark respiration rate and maximum quantum efficiency of PS II, and nitrate reductase activity of roots. Additionally, root morphology such as total roots length, surface area, specific root area and specific root length was also stimulated by night warming. In contrast, night warming decreased concentrations of non-structural carbohydrate in leaves and roots of both species in autumn. The present study demonstrates that night warming would enhance late autumn leaf photosynthetic rate, and increase N uptake capacity of roots.
•Night warming effects on coniferous trees in later growing season were investigated.•Root net influxes of NH4+ and NO3− in Picea asperata were increased by night warming.•Night warming has positive effect on foliar gas exchange as well as root morphology.•High leaf photosynthesis rate companied by high nutrient uptake capacity of root.
Shading is one of the most chronic restrains which can lead to the lodging of intercropped plants. In order to increase the soybean stem lodging resistance, a 2-year field trial was conducted to ...evaluate the impact of different ratios and concentrations of NH
4
+
/NO
3
–
on the morpho-physiological and biochemical characteristics of soybean stem under shade conditions. The total 5 ratios of NH
4
+
/NO
3
–
were applied as follows: T0 = 0/0 (control), T1 = 0/100 (higher ratio), T2 = 25/75 (optimum), T3 = 50/50 (optimum), and T4 = 75/25 (higher ratio) as a nitrogen source. Our findings displayed that the T2 (25/75) and T3 (50/50) treatments alleviated the shading stress by improving the photosynthetic activity, biomass accumulation, carbohydrates contents, and lignin related enzymes (POD, CAD, and 4Cl) which led to improvement in stem lodging resistance. The correlation analysis (
p
≤ 0.05,
p
≤ 0.01) revealed the strong relationship between lodging resistance index and stem diameter, stem strength, lignin content, photosynthesis, and lignin related enzymes (POD, CAD, and 4CL) evidencing the strong contribution of lignin and its related enzymes in the improvement of lodging resistance of soybean stem under shade conditions. Collectively, we concluded that optimum NH
4
+
/NO
3
–
ratios (T2 and T3) can boost up the lodging resistance of soybean stem under shade stress.
BACKGROUND AND AIMS: The Root is an important plant organ and has high heterogeneity; how it responds to global warming is yet to be answered. This study examined the growth and physiological ...responses of fine roots to warming around the non-growing season. METHODS: Plants from 4-year-old Picea asperata were grown under experimental warming conditions. A detailed investigation was conducted by measuring biomass, triphenyltetrazolium chloride (TTC) reducing capacity, carbon (C) and nitrogen (N) concentration, non-structural carbohydrate (NSC) of the primal five branch order roots in early (April) and late (September) growing seasons as well as in the non-growing season (December). RESULTS: Warming promoted fine root growth in April and fine root turnover was mostly in the first four orders. It decreased root C, N concentration in the early and late growing seasons but increased N concentration in the non-growing season. Moreover, it increased NSC concentration (especially soluble sugar) in April but decreased its concentration (soluble sugar and starch) in December. TTC reducing capacity in April was higher than in the other 2 months. CONCLUSIONS: The effect of warming on tree roots varied with its branch order and month. The lower order (first three or four order, in general) roots were sensitive to warming, especially in April (early part of growing season) and December (non-growing season). Warming accelerated the carbon input from root to soil. It is indicated that any changes in winter temperatures could alter the sink strength of terrestrial ecosystems considerably. Moreover, TTC reducing capacity could reflect more information about root, but it was more sensitive than N concentration.
Although thyroid dysfunction caused by Hashimoto's thyroiditis (HT) is believed to be related to implantation failure due to the underdevelopment of the receptive uterus, it is unknown whether HT ...itself, even in the euthyroid state, impairs embryo implantation associated with endometrial receptivity defects. To address whether HT itself can affect endometrial receptivity accompanied by implantation alterations, a euthyroid HT model was established in mice.
Female NOD mice were immunized twice with thyroglobulin and adjuvant to induce the experimental HT model. Four weeks after the second treatment, the mice were normally mated, and pregnant ones were sacrificed in implantation window for thyroid-related parameter and steroid hormones measurements by electrochemiluminescence immunoassay and enzyme-linked immunosorbent assay and implantation site number calculation by uptake of Chicago Blue dye. In addition, certain morphological features of endometrial receptivity were observed by hematoxylin-eosin staining and scanning electron microscopy, and the expression of other receptivity markers were analyzed by immunohistochemistry, RT-qPCR or Western Blot.
HT mice displayed intrathyroidal monocyte infiltration and elevated serum thyroid autoantibody levels without thyroid dysfunction, defined as euthyroid HT in humans. Euthyroid HT resulted in implantation failure, fewer pinopodes, retarded pinopode maturation, and inhibited expression of receptivity markers: estrogen receptor α (ERα), integrin β3, leukemia inhibitory factor (LIF), and cell adhesion molecule-1 (ICAM-1). Interestingly, despite this compromised endometrial receptivity response, no statistical differences in serum estradiol or progesterone level between groups were found.
These findings are the first to indicate that HT induces a nonreceptive endometrial milieu in the euthyroid state, which may underlie the detrimental effects of HT itself on embryo implantation.
We exposed cuttings of two poplar species,
Populus cathayana Rehder and
Populus przewalskii Maximowicz, from Sect.
Tacamahaca Spach to two watering regimes (well-watered and water-stressed ...conditions) and to two nutrient regimes (with or without fertilization) in a greenhouse to determine how fertilization affects the growth, morphology and physiology of poplars under different water conditions. Under stress conditions, changes in early growth and dry matter allocation, and decrease in gas exchange and the related functions are usually observed. Moreover, the measurement of carbon isotope composition (δ
13C) provides an integrated measurement of water use efficiency. And abscisic acid (ABA) is a phytohormone which plays a prominent role in various physiological and biochemical processes related to environmental stresses. So we determine these characteristics and related parameters, and our results showed the following: (1) Fertilization promoted the growth of poplars under well-watered conditions, while under water-stressed conditions its effect on growth was negative. (2) Fertilization increased δ
13C, total N concentration, chlorophyll a/b and intrinsic efficiency of photosystem II (Fv/Fm) but decreased relative water content of leaves, stomatal conductance, transpiration rate and C/N ratio under both well-watered and water-stressed conditions. (3) Fertilization appeared to increase net photosynthesis rate and decrease ABA content under well-watered conditions, while it decreased net photosynthesis rate and increased ABA content under water-stressed conditions. Moreover, compared to
P.
cathayana, collected from a lower altitude region,
P.
przewalskii, collected from a high-altitude region, has a slower growth rate and stronger adaptability to drought stress, which perhaps resulted from its chronic adaptability to the low water availability of high-altitude region; but to the nutrient stress, there was no difference between the two species.
We have limited understanding of root foraging responses when plants were simultaneously exposed to nutrient heterogeneity and competition, and our goal was to determine whether and how plants ...integrate information about nutrients and neighbors in root foraging processes.
The experiment was conducted in split-containers, wherein half of the roots of spruce (Picea asperata) seedlings were subjected to intraspecific root competition (the vegetated half), while the other half experienced no competition (the non-vegetated half). Experimental treatments included fertilization in the vegetated half (FV), the non-vegetated half (FNV), and both compartments (F), as well as no fertilization (NF). The root architecture indicators consisted of the number of root tips over the root surface (RTRS), the length percentage of diameter-based fine root subclasses to total fine root (SRLP), and the length percentage of each root order to total fine root (ROLP). The target plants used novel root foraging behaviors under different combinations of neighboring plant and localized fertilization. In addition, the significant increase in the RTRS of 0-0.2 mm fine roots after fertilization of the vegetated half alone and its significant decrease in fertilizer was applied throughout the plant clearly showed that plant root foraging behavior was regulated by local responses coupled with systemic control mechanisms.
We measured the root foraging ability for woody plants by means of root architecture indicators constructed by the roots possessing essential nutrient uptake ability (i.e., the first three root orders), and provided new evidence that plants integrate multiple forms of environmental information, such as nutrient status and neighboring competitors, in a non-additive manner during the root foraging process. The interplay between the responses of individual root modules (repetitive root units) to localized environmental signals and the systemic control of these responses may well account for the non-additive features of the root foraging process.
Our knowledge of grassland biomass and its relationships with abiotic and biotic factors on eastern margin of the Tibetan Plateau is extremely limited. Here, we measured above-ground biomass (AGB), ...below-ground biomass (BGB) and root/shoot ratio (R/S) of alpine meadow, and explored their driving factors, including abiotic factors (altitude and slope properties, and climate) and biotic factors (plant community properties) based on field survey from 53 sites on eastern margin of the Tibetan Plateau. The results showed that the median values of AGB, BGB and R/S of alpine meadow in this region were 284.44 g m−2, 2232.98 g m−2 and 7.31, respectively. 85.42% of total biomass allocated to below-ground and 87.13% of BGB distributed in top soil (i.e. 0–20 cm). There was no significant correlation between AGB and BGB. AGB did not change, while BGB and R/S related downward quadratically with increasing altitude; AGB significantly linearly decreased, but BGB and R/S changed upward quadratically along slope gradient. Temperature and precipitation had no effect on AGB but significantly influenced BGB and R/S. AGB was positively linearly correlated with community height and coverage, and BGB was negatively linearly correlated with community height, while R/S was negatively linearly correlated with community height and coverage. There was no relationship between plant biodiversity and grassland biomass. The contribution of biotic factors on grassland biomass was higher than abiotic factors at the present scale. This study highlighted the importance of below-ground parts in alpine grasslands, and could provide useful information for understanding the determining factors for grassland biomass in the Tibetan Plateau.
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•AGB did not change while BGB showed a downward quadratic relationship with increasing altitude.•AGB significantly linearly decreased, but BGB had an upward quadratic pattern along slope gradient.•BGB is influenced by the combined effects of temperature and precipitation.•AGB correlated positively with plant community height and coverage, BGB correlated negatively with height.•The contribution of abiotic factors on grassland biomass was higher than biotic factors.
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