Wenguang Ma

An Enhanced Drought-Tolerant Method Using SA-Loaded PAMPS Polymer Materials Applied on Tobacco Pelleted Seeds

Drought is one of the most important stress factors limiting the seed industry and crop production. Present study was undertaken to create novel drought-resistant pelleted seeds using the combined materials with superabsorbent polymer, poly(2-acrylamide-2-methyl propane sulfonic acid) (PAMPS) hydrogel, and drought resistance agent, salicylic acid (SA). The optimized PAMPS hydrogel was obtained as the molar ratio of 2-acrylamido-2-methyl-propanesulfonic acid (AMPS) to potassium peroxydisulfate (KPS) and N, N′-methylene-bis-acrylamide (MBA) was 1 : 0.00046 : 0.00134. The hydrogel weight after swelling in deionized water for 24 h reached 4306 times its own dry weight. The water retention ratio (RR) of PAMPS was significantly higher as compared with the control. It could keep as high as 85.3% of original weight after 30 min at 110°C; even at 25°C for 40 d, the PAMPS still kept RR at 33.67%. PAMPS disintegration ratio increased gradually and reached around 30% after embedding in soil or activated sludge for 60 d. In addition, there were better seed germination performance and seedling growth in the pelleted treatments with SA-loaded PAMPS hydrogel under drought stress than control. It suggested that SA-loaded PAMPS hydrogel, a nontoxic superabsorbent polymer, could be used as an effective drought resistance material applied to tobacco pelleted seeds.

“Intelligent” seed pellets may improve chilling tolerance in tobacco

Tobacco seeds and seedlings often encounter low temperature stress in China. An ‘intelligent’ tobacco seed pellet was developed to improve chilling tolerance by adding thermo-sensitive PNIPAAm-co-BMA (poly(N-isopropylacrylamide-co-butyl methacrylate)) hydrogel. PNIPAAm-co-BMA can detect changes in environmental temperature and change its reticular structure accordingly. In addition, the release rate of salicylic acid (SA) loaded in PNIPAAm-co-BMA hydrogel is changed. Tobacco seeds of two different chilling-tolerant tobacco varieties were pelleted by SA-loaded PNIPAAm-co-BMA, and then the germination characteristics, seedling quality and some physiological parameters of the seeds and seedlings were measured after a chilling stress at 11°C for 5 d. The results showed that the germination percentage (GP), germination index (GI), root length, seedling dry weight and the activities of POD (peroxidase) were significantly increased and the concentration of MDA (malondialdehyde) was significantly decreased in the ‘intelligent’ seed pellets compared with the seeds without SA and PNIPAAm-co-BMA in both varieties. The results showed that the ‘intelligent’ seed pellets had thermo-sensitive traits; they enhanced and prolonged the efficiency and acting time of loaded SA. This indicated that the ‘intelligent’ seed pellets pelleted with SA-loaded PNIPAAm-co-BMA could be used to improve chilling tolerance.

Evaluation of seed quality based on changes of internal substances during tobacco seed (Nicotiana tabacum L.) development

Seed quality is closely associated with internal substances during seed development. Tobacco seed varieties Honghua Dajinyuan (HD) and Yunyan97 (Y97) had higher viability and vigor when harvested from 31 to 33 days after pollination (DAP), subsequently decline slightly on 35 DAP. From 7 to 35 DAP, the moisture content of HD and Y97 decreased sharply from 90 to 30%, and abscisic acid declined more than 80% totally in seeds. Accumulation of oil and protein was accompanied with the consumption of soluble sugar and starch, especially from 7 to 23 DAP. In addition, crude fiber and arginine exhibited an increasing trend, while ash and lysine significantly decreased from 7 to 23 DAP. Generally, the germination percentage (seed viability) in HD and Y97 seed was related to oil, moisture, soluble sugar, protein, starch, ABA, lysine, arginine, seed weight and seed coat color; however, only moisture, oil and protein had a significant correlation with vigor index (seed vigor). Thus, seed viability could be applied to estimate the relationship between internal substances and seed quality, and predict the optimum seed harvest time of tobacco.

Suppression of LOX activity enhanced seed vigour and longevity of tobacco (Nicotiana tabacum L.) seeds during storage

Abstract The preservation of seed viability and quality in storage is an important trait both for commercial and germplasm usage. To better explore potential mechanisms of tobacco seed deterioration, seed packed in cloth bag (C) and vacuum bag (V) were stored under room temperature (RT) and low temperature (LT, 18°C), and sampled periodically for laboratory testing. Seed stored in low temperature with vacuum bag (LT/V) owned the highest seed vigour after 25 months of storage and in room temperature with cloth bag (RT/C) lost seed vigour and germination ability after 20-month storage. Meanwhile, seed in RT/C notably increased about 5-fold endogenous hydrogen peroxide (H2O2), 4-fold malondialdehyde (MDA) contents, 12-fold Lipoxygenases (LOX) activity and 2-fold the expression of NtLOX3 comparing with LT/V at the end of 15-month storage. In addition, regression analysis indicated that LOX activity was strongly negatively correlated with seed vigour as the R2 value reached 0.970 in RT/C. Furthermore, caffeic acid and catechin, the inhibitors of LOX activity, were applied to tobacco seeds pre-treatment and followed with artificial accelerated aging. Seeds pretreated with inhibitors, especially caffeic acid, reduced LOX activity by 50%, MDA and H2O2 contents by 40% and 20%, respectively, and increased more than 1.2-fold seed vigour and seedling quality comparing with seeds pretreated with H2O after 6-day artificial aging, indicating a better seed storability after artificial accelerated aging. These results suggest that LOX accelerated seed aging, and suppression of LOX activity enhanced seed vigour and viability in accelerated aging tobacco seed, opening new opportunities for effective management of seed germplasm under long-term storage and conservation.