Melatonin mitigates cadmium toxicity by promoting root development, delaying root senescence, and regulating cadmium transport in cotton.

Cd ions are absorbed and transported from the soil by crop roots, which are the first organ to be exposed to Cd. This results in an increase in cadmium ions in crops, significantly affecting crop growth and yield. Exogenous melatonin (MT) can help reduce cadmium (Cd) stress in cotton, but the specific contribution of roots to this process remains unclear. In order to address this knowledge gap, an in-situ root phenotyping study was conducted to investigate the the phenotype and lifespan of roots under cadmium stress (Cd) and melatonin treatment (Cd + MT). The results showed that MT alleviated the decreases in plant height, leaf area, SPAD value, stem diameter, stomatal conductance and net photosynthetic rate under Cd stress, which further promoted the biomass accumulation in various cotton organs. What is more, the Cd + MT treatment increased root volume, surface area, and length under Cd stress by 25.63 %, 10.58 %, and 21.89 %, respectively, compared with Cd treatment. Interestingly, compared to Cd treatment, Cd + MT treatment also significantly extended the lifespan of roots and root hairs by 6.68 days and 2.18 days, respectively. In addition, Cd + MT treatment reduced the transport of Cd from roots to shoots, particularly to bolls, and decreased the Cd bioconcentration factor in bolls by 61.17 %, compared to Cd treatment. In conclusion, these findings show that applying MT externally helps reduce Cd stress by delaying root senescence, promoting root development and regulating Cd transport. This method can be an effective approach to managing Cd stress in cotton.

[Effects of NaCl stress on Hovenia dulcis and Gleditsia sinensis seedlings growth, chlorophyll fluorescence, and active oxygen metabolism].

With potted Hovenia dulcis and Gleditsia sinensis seedlings as test materials, their plant growth, chlorophyll fluorescence characteristics, and active oxygen metabolism under stress of different concentration (0, 0.15%, 0.30%, 0.45%, and 0.60%) NaCl were studied. The results showed that with increasing concentration of NaCl, the plant growth, leaf chlorophyll content, photochemical efficiency of PS II (Fv/Fm), quantum yield of PS II (phi(PS II)), and photochemical quenching (q(P)) decreased gradually, while the non-photochemical quenching of fluorescence (q(N)) was in adverse. After 10 days of 0. 15% NaCl stress, the leaf chlorophyll content, Fv/Fm, phi(PS II), and q(P) of H. dulcis seedlings decreased by 19.77%, 2.94%, 29.03%, and 8.16%, respectively, with significant differences (P<0.05) to the control, while no significant differences were observed for G. sinensis seedlings. Compared with the control, the Fv/Fm and phi(PS II), of G. sinensis seedlings in treatment 0.30% NaCl decreased significantly by 1.91% and 14.66%, and the chlorophyll content and q(P) of the seedling in treatment 0.45% NaCl decreased significantly by 29.28% and 11.36%, respectively (P<0.05). With increasing concentration of NaCl, the SOD activity of G. sinensis seedlings showed a consistent increasing trend, and that of H. dulcis seedlings increased first and decreased then. The POD and CAT activities of G. sinensis and H. dulci seedlings tended to increase first and decrease then, with the increment being higher for G. sinensis than for H. dulci, while the MDA content of the seedlings had an increasing trend, with the increment being higher for H. dulcis than for G. sinensis, suggesting that the cell membrane lipid peroxidation of H. dulcis was more serious than that of G. sinensis. It was concluded that G. sinensis had greater salt tolerance than H. dulcis, which was related toits higher anti-oxidation enzyme activities.

[Histological observation on programmed cell death in wheat-leaf rust fungus intreaction].

The biochemical character of PCD in different interaction between wheat and Puccinia recondita f. sp tritici was observed using DNA agarose gel electrophoresis and end labeling in situ (Terminal Deoxynucleotidyl Transferase-mediated dUTP Nick End TUNEL). The DNA ladder, which is the typical character of programmed cell death(PCD), was observed in incompatible combination (cv.lorvin10 x race 162) and the positive reaction in wheat leaves of incompatible combination since 12h after inoculation also appeared. The results, coupled with the previous study, indicated that HR was a typical form of PCD in incompatible combination between wheat and wheat leaf fungus.

[Histological observation on programmed cell death in wheat--leaf rust fungus intreactioin].

The ultrastructural features of mesophyll cell surrounding the fungus in different interaction between wheat and Puccinia recondita f. sp tritici were observed with transmission electron microscopy. In incompatible combination(cv. lorvin 10 x race 162), the nuclei gradually became irregular with highly condensed chromatin towards the nuclear envelope, while the chloroplast became swelling since 12 h to 24 h after inoculation(a.i.). At 48 h a.i., the condensation of the chromatin became more prominent and the chloroplast began to disintegrate. Finally, when some mitochondria started to degrade at 72 h a.i., the nuclei and the chloroplast became disruption completely. During the process, endoplasmic reticulum and vesicles did play a vital role in the further degeneration of other organelles and protoplasmic components just similar to the lysosome acting in the animal cells. These results suggest that the ultrastructural feature of cell death is a form of programmed cell death (PCD). In compatible combination (cv. lorvin 10 x race 165), ultrastructural of mesophyll cell exhibited different features from incompatible combination. At 24 h a.i., the plasmic membrane showed sunken and the chloroplast slightly exhibited swelling. Since 48 h to 72 h a.i., most of the swelling chloroplasts were observed while the other organelles still remained unaltered. At the same time, the hypha and haustorium mother cell in the intracellular space also could be observed.