Foliar uptake screening: A promising strategy for identifying wheat varieties with low lead accumulation.

Lead (Pb) contamination in wheat grain is of great concern, especially in North China. Atmospheric deposition is a major contributor to Pb accumulation in wheat grain. Screening low Pb accumulating wheat varieties has been an effective method for addressing Pb contamination in wheat grain. However, identifying wheat varieties with low Pb accumulation based on foliar uptake of atmospheric Pb has been neglected. Therefore, two field trials with distinct atmospheric Pb deposition were conducted to screen for stable varieties with low Pb accumulation. It was verified that YB700 and CH58, which have high thousand-grain weights and stable low Pb accumulation in field 1 (0.19 and 0.13 mg kg-1) and field 2 (0.17 and 0.20 mg kg-1), respectively, were recommended for cultivation in atmospheric Pb contaminated farmlands in North China. Furthermore, indoor experiments were conducted to investigate Pb uptake by the roots and leaves of different wheat varieties. Our findings indicate that Pb accumulation in different wheat varieties is primarily influenced by foliar Pb uptake rather than root Pb uptake. Interestingly, there was a positive correlation (p < 0.05) between the Pb concentrations in leaves and the stomatal width and trichome length of the adaxial epidermal surface. Additionally, there is a positive correlation (p < 0.01) between the Pb concentration in the wheat grain and trichome length. In conclusion, the screening of wheat varieties with narrower stomatal widths or shorter trichomes based on foliar uptake pathways is an effective strategy for ensuring food safety in areas contaminated by atmospheric Pb.

[Distribution and Transport of Cadmium and Arsenic in Different Aboveground Parts of Wheat After Flowering].

To investigate the effects of leaves and stems on the accumulation and transport of cadmium(Cd) and arsenic(As) in wheat shoots after flowering, a field experiment was conducted in a typical Cd and As co-contaminated agricultural land to explore the distribution and translocation of Cd and As in the different parts of two wheat cultivars after flowering. The results showed that Cd was mainly distributed in the nodes of two varieties, and the translocation factors of Cd from internode 3 to node 2, from internode 2 to node 1, and from sheath 1 to node 1 were markedly higher than those of other aboveground parts during the grain-filling stage. However, Cd was mainly distributed in the leaves, and the translocation factors of Cd from sheath to leaf and from node 1 to rachis was significantly higher than those of other parts at the mature stage. In addition, the transport capacity of Cd from glume to rachis and from rachis to grain in JM22 was significantly lower than that in SN28, which significantly reduced Cd concentrations in the rachis, glume, and grain of JM22 by 22.3%, 40.8%, and 44.4%, respectively. Meanwhile, As was mainly distributed in the wheat leaves from the grain-filling stage to the mature stage, and As concentrations in the glume and grain of JM22 were 25.8% and 33.3% lower than those of SN28, respectively. Additionally, the translocation factors of As from the sheath to the node were significantly 438% and 190% higher than that from leaf to sheath and from node to internode during the whole grain filling stage and mature stage. Moreover, the translocation factors of As from glumes to grains and from rachis to grains in JM22 were 40.6% and 44.4% lower than that in SN28, respectively. In summary, flag leaf, node 1, and the rachis had regulated Cd transport and accumulation in wheat grains, whereas leaf 3, flag leaf, node 1, the glumes, and the rachis were mainly responsible for As transport and accumulation in wheat grains.

Mechanism of Pb accumulation in Chinese cabbage leaves: Stomata and trichomes regulate foliar uptake of Pb in atmospheric PM2.5.

Chinese cabbage (Brassica rapa ssp. pekinensis) is one of the most popular and frequently consumed leafy vegetables. It was found that atmospheric PM2.5-Pb contributes to Pb accumulation in the edible leaves of Chinese cabbage via stomata in North China during haze seasons with high concentrations of fine particulate matter in autumn and winter. However, it is unclear whether both stomata and trichomes co-regulate foliar transfer of PM2.5-Pb from atmospheric deposition to the leaf of Chinese cabbage genotypes with trichomes. Field and hydroponic experiments were conducted to investigate the effects of foliar uptake of PM2.5-Pb on Pb accumulation in leaves using two genotypes of Chinese cabbage, one without trichomes and one with trichomes. It was verified that open stoma is a prominent pathway of foliar PM2.5-Pb transfer in the short-term exposure for 6 h, contributing 74.5% of Pb accumulation in leaves, whereas Pb concentrations in the leaves of with-trichome genotype in the rosette stage were 6.52- and 1.04-fold higher than that of without-trichome genotype in greenhouse and open field, respectively, which suggests that stomata and trichomes co-regulate foliar Pb uptake of from atmospheric PM2.5. Moreover, subcellular Pb in the leaves was distributed in the following order of cytoplasm (53.8%) > cell wall (38.5%)> organelle (7.8%), as confirmed through high-resolution secondary ion mass spectrometry (NanoSIMS). The Leadmium™ Green AM dye manifested that Pb in PM2.5 entered cellular space of trichomes and accumulated in the basal compartment, enhancing foliar Pb uptake in the edible leaves of cabbage. The results of these experiments are evidence that both stomata and trichomes are important pathways in the regulation of foliar Pb uptake and translocation in Chinese cabbage.

Bioimaging of Pb by LA-ICP-MS and Pb isotopic compositions reveal distributions and origins of Pb in wheat grain.

Atmospheric heavy metal deposition in agroecosystems has increased recently, especially in northern China, which poses serious risks to crop safety and human health via food chain. Wheat grains can accumulate high levels of Pb even when wheat is planted in soils with low levels of Pb. However, the influence of atmospheric deposition on the accumulation and distribution of Pb in wheat grain is still unclear. A field survey was conducted in three districts (A: a district with industrial and traffic pollution; B: a district with traffic pollution; and C: an unpolluted district) in Hebei Province, North China. The grain of wheat cultivated in district A accumulated more Pb from soil and atmospheric deposition than those in other districts, and the bran from district A contained 3.50 and 2.04 times more Pb than those from districts B and C, respectively. The Pb distribution pattern in wheat grain detected by laser ablation inductively coupled mass spectrometry (LA-ICP-MS) was characterized by accumulation mostly in the pericarp and seed coat rather than in the crease, embryo and endosperm. Furthermore, Pb isotopic data showed that airborne Pb was the major source (>50%) of Pb in wheat grain. Interestingly, average contributions of Pb from atmospheric deposition to white flour (78.22%) were higher than its contributions to bran (56.27%). In addition, wheat flag leaves were exposed to PbSO4 at the booting stage, and much greater Pb accumulation (0.33-0.48 mg/kg) was observed in exposed wheat grain than in the control (P < 0.05), PbSO4 constituted most (82.80-100%) of the Pb in the wheat grain. In summary, the results confirmed the efficient foliar Pb uptake and transfer from atmospheric deposition into wheat grain. It would be a new sight for understanding the contribution of airborne Pb to Pb accumulation in wheat grains.

Contribution of PM2.5-Pb in atmospheric fallout to Pb accumulation in Chinese cabbage leaves via stomata.

Foliar uptake of Pb is especially important when Chinese cabbage (Brassica rapa spp. pekinensis), having a large leaf surface area, is cultivated in North China during seasons with heavy haze. However, the mechanisms of foliar Pb uptake via stomata by Chinese cabbage exposed to atmospheric fallout are unclear. A field experiment was conducted to explore the impacts of Pb in particulate matter with sizes ≤ 2.5 µm (PM2.5-Pb) from atmospheric fallout to Pb accumulation in cabbage leaves through stomata. Cabbage varieties with low-Pb-accumulation (LPA) and high-Pb-accumulation (HPA) were examined using inductively coupled plasma-mass spectrometry and scanning electron microscopy/energy-dispersive X-ray analysis. The 206Pb/207Pb and 208Pb/207Pb ratios of PM2.5, plants, and soil demonstrated that the major source of Pb in cabbage leaves was PM2.5. The average width and length of the stomatal apertures were 7.14 and 15.61 µm for LPA cabbage and 8.10 and 16.64 µm for HPA cabbage, which are large enough for PM2.5-Pb to enter the leaves. The HPA cabbage had significantly higher stomatal width-to-length ratios than the LPA cabbage, indicating that the former trapped much more PM2.5-Pb and accumulated more Pb. These results clarify the contributions of the stomatal characteristics to PM2.5-Pb accumulation in the edible parts of Chinese cabbage.

[Glottic measurement and vocal evaluation before and after adult arytenoidectomy].

OBJECTIVE: To study minimal glottic area which can acquire sufficient airway for decannulation and maximal glottic area which can maintain preoperative vocal function on adult bilateral vocal cord paralysis with unilateral arytenoidectomy. METHODS: Sixteen adult received microscopic right arytenoidectomy with Diomed-25 laser under general anaesthesia and sustained laryngoscope from September 1998 to February 2003. The pre-postoperative glottic measurement and vocal acoustic parameters were analyzed. RESULTS: The postoperative maximal glottic area, maximal posterior glottic width and maximal opening angle between bilateral vocal cords of the 15 decannulated cases were (45.93 +/- 6.56) mm2, (4.97 +/- 0.73) mm and (24.34 +/- 4.74) degrees respectively. Compared with preoperative period, there were significant difference. Pre-postoperative acoustic parameters (Jitter, Shimmer, harmonics-noise ratio) were analyzed and no significant difference were found (P > 0.05, but there are significant difference in NNE (normalized noise energy) and MPT (maximum phonation time) (P < 0.05). Except for three cases whose postoperative glottic area were more than 50. 1 mm2, there were no significant difference in pre and postoperative NNE (P > 0.05). The minimal glottic area decannulated was 38.0 mm2. The more opening maximal glottic area, the greater of NNE because of bigger closing gap. Noticeable increase of NNE was observed when maximal opening glottic area was up to 50.1 mm2. CONCLUSIONS: The minimal glottic area for decannulation should be 38.0 mm2, and the maximal glottic area for maintaining preoperation vocal function should be 50.1 mm2 on adult bilateral voca cord paralysis with laser aryntenoidectomy.

[Diagnosis and management of sulcus vocalis].

OBJECTIVE: To clarify the pathophysiology of sulcus vocalis and to develop a more rational approach to treatment. METHODS: Twenty-nine cases of sulcus vocalis patients were divided into three classification: Type I is a physiologic variant and no dysphonia (11 cases). Types II (sulcus vergeture, 13 cases) and III (sulcus vocalis, 5 cases) are characterized by severe dysphonia and loss of vibratory activity. Eighteen cases of dysphonia were treated by surgery and phonation training. The operations included fat injection into vocal cords (9 cases of types II and 1 cases of types III, including 1 case of types III of second operation), fat implantation into sulcus vergeture after incision (4 cases of types II and 1 cases of types III) and undermining of the mucosa and sulcus vocalis resection (4 cases of types III, including 1 case of second operation). Phonatory function and video laryngostroboscopic data were evaluated before and after surgery and phonation training treatment in 18 patients. The mean follow-up time was 15.3 months. RESULTS: Ten cases of types II had excellent results after fat injection into vocal cords (n = 6) and fat implantation into sulcus vergeture after incision (n = 4). Three cases of types II improved after fat injection into vocal cords. Three cases of type III had excellent results after sulcus vocalis resection. One case of type III had excellent results by Second operation (sulcus vocalis resection) after fat injection into vocal cord. One case of type III improved by Second operation (fat injection into vocal cords) after fat implantation into sulcus vergeture after incision. No postoperative complications were noted. CONCLUSION: Accurate classification of sulcus vocalis is important and then adapt treatment to different types. Fat implantation into sulcus vergeture to type II and sulcus vocalis resection to type III were the best choice methods.