The enhancement of drought tolerance for pigeon pea inoculated by arbuscular mycorrhizae fungi

  Pigeon pea (Cajanus cajan) has been rapidly grown in the drought-striken Karst regions of southwest China. Present research aimed to investigate the effects of arbuscular mycorrhizae (AM) on the drought tolerance of pigeon pea, as well as to elucidate the physiological responses of AM-colonized seedlings to the water deficit. As subjected to drought stress, AM symbiosis (AMD) highly led to the positive effects on root system, plant height and stem diameter. AMD demonstrated a remarkably higher chlorophyll content, photosynthetic rate and stomatal conductance. The soluble sugar in AMD was significantly higher than that of the non-AM seedlings (NAMD), indicating the enhanced tolerance at least partially correlated with osmotic solute. Conversely, the proline (Pro) of AMD was lower, revealing the excessive Pro was not imperative for drought tolerance. After 30 days drought stress, AMD gave around a third less lipid peroxides than that of NAMD. Rather, the root activities of AMD were significantly higher than that of the latter after 10 days drought stress. Thereby, AM fungi might substantially elevate the tolerance to drought of pigeon pea, and the cumulative effects contributed to the enhanced tolerance. To date, this has been the first report concerning the enhancement of drought tolerance via AM colonization in this legume species.  

Vasoactive Components of Dialysis Solution

Background Conventional peritoneal dialysis (PD) solutions elicit vasodilation, which is implicated in the variable rate of solute transport during the dwell. The components causing such vasoactivity are still controversial. This study was conducted to define the vasoactive components of conventional and new PD solutions. Methods Three visceral peritoneal microvascular levels were visualized by intravital video microscopy of the terminal ileum of anesthetized rats. Anesthesia-free decerebrate conscious rats served as control. Microvascular diameter and blood flow by Doppler measurements were conducted after topical peritoneal exposure to 4 clinical PD solutions and 6 prepared solutions designed to isolate potential vasoactive components of the PD solution. Results All clinically available PD solutions produced a rapid and generalized vasodilation at all intestinal microvascular levels, regardless of the osmotic solute. The pattern and magnitude of this dilation was not affected by anesthesia but was determined by arteriolar size, the osmotic solute, and the solution's buffer anion system. The greatest dilation occurred in the small precapillary arterioles and was elicited by conventional PD solution and heat re-sterilized solution containing low glucose degradation products (GDPs). Hypertonic mannitol solutions produced a dilation that was approximately 50% less than the dilation obtained with glucose solutions with identical osmolarity and buffer. Increasing a solution's osmolarity did not produce a parallel increase in the magnitude of dilation, suggesting a nonlinear relationship between the two variables. Lactate dissolved in an isotonic solution was completely non-vasoactive unless the solution's H+ concentration was increased. At low pH, isotonic lactate produced a rapid but transient vasodilation. This vascular reactivity was similar in magnitude and pattern to that obtained with the isotonic 7.5% icodextrin solution (Extraneal; Baxter Healthcare, Deerfield, Illinois, USA). Conclusions ( 1 ) Hyperosmolarity is the major vasoactive component of PD solution. ( 2 ) Hyperosmolarity and active intracellular glucose uptake account together for approximately 75% of PD solution-induced dilation, whereas GDPs contribute to approximately 25%. ( 3 ) Lactate is vasoactive only at low pH (high [H+]). ( 4 ) The magnitude of PD solution-mediated vasodilation is partially dependent on the nature of the osmotic solute, the GDP contents, and the [H+], which determine the vasoactivity of the lactate-buffer anion system. Studies are required to define the molecular mechanisms of PD-induced vasodilation and to determine the vasoactive properties of these solutions after chronic infusion.