Hydrogen sulfide promotes root organogenesis in Ipomoea batatas, Salix matsudana and Glycine max.

In this report, we demonstrate that sodium hydrosulfide (NaHS), a hydrogen sulfide (H(2)S) donor, promoted adventitious root formation mediated by auxin and nitric oxide (NO). Application of the H(2)S donor to seedling cuttings of sweet potato (Ipomoea batatas L.) promoted the number and length of adventitious roots in a dose-dependent manner. It was also verified that H(2)S or HS(-) rather than other sulfur-containing components derived from NaHS could be attributed to the stimulation of adventitious root formation. A rapid increase in endogenous H(2)S, indole acetic acid (IAA) and NO were sequentially observed in shoot tips of sweet potato seedlings treated with HaHS. Further investigation showed that H(2)S-mediated root formation was alleviated by N-1-naphthylphthalamic acid (NPA), an IAA transport inhibitor, and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), an NO scavenger. Similar phenomena in H(2)S donor-dependent root organogenesis were observed in both excised willow (Salix matsudana var. tortuosa Vilm) shoots and soybean (Glycine max L.) seedlings. These results indicated that the process of H(2)S-induced adventitious root formation was likely mediated by IAA and NO, and that H(2)S acts upstream of IAA and NO signal transduction pathways.

[Kinetics of hemoglobin carrying and releasing oxygen].

The purpose of the present study was to examine the kinetic process of hemoglobin (Hb) carrying and releasing oxygen. Under the standard conditions (pH 7.4, Po(2) 20 mmHg, 20 °C) the blood samples of chicken, rabbit, frog and carp were equilibrated in oxygen content analyzer with calibrated gas mixture A (0.5% CO(2) and 99.5% N(2)). Then the blood samples were exposed to gas mixture B (21% O(2), 0.5% CO(2) and 78.5% N(2)). After equilibration, the blood samples were exposed to gas mixture A again. During the whole process, Po(2) of blood samples was detected in real-time. The time spent in blood Po(2) changing from 0 to 21 kPa was recorded carefully. The results indicated that the kinetic curve of Hb carrying oxygen presented a shape of "S". It was similar to the Hb oxygen dissociation curve (Hb ODC). Based on the curve, T(50), a new kinetic parameter, was established. T(50) is the time of 50% O(2) saturation of Hb. It can reflect the efficiency of Hb carrying oxygen. Through comparing of T(50), the efficiency of Hb carrying oxygen among 4 species of animals was: frog < carp < rabbit < chicken. In the phase I of Hb carrying and releasing oxygen kinetic curve, the slope in carp was much larger than that in rabbit; the time [(1 411±6) s] of Hb releasing oxygen in chicken was longer than that in other 3 animals. These differences reflected the variety of efficiency of Hb carrying and releasing oxygen. In addition, the kinetic features of Hb carrying oxygen were likely to become an important index to evaluate the function of Hb carrying oxygen, especially in evaluating the ability of artificial blood substitute. On the basis of the analysis of the kinetic curve of Hb carrying oxygen and Hb ODC, another new important efficacy parameter E(50) was proposed. E(50) reflects the relationship between the time of 50% O(2) saturation of Hb and environmental Po(2). E(50) can be used as a synthetic index to assess the efficiency of Hb carrying oxygen.