2种过路黄抗旱生理特性的研究

以过路黄与金叶过路黄为材料,通过盆栽干旱胁迫,同时以正常浇水处理为对照,研究了不同程度干旱胁迫对过路黄与金叶过路黄叶片的质膜透性、保护酶活性、渗透调节物质的影响.结果表明,在干旱胁迫下,过路黄与金叶过路黄叶片的质膜透性上升;超氧化物歧化酶(SOD)、过氧化物酶(POD)活性先上升,后下降;脯氨酸、可溶性蛋白含量增加,只是变化的幅度和进程不同.经几项生理指标的综合分析,得出过路黄比金叶过路黄具有较强的抗旱能力.     

The Effects of Air Exposure on Hemolymph Osmoregulatory Capacity of Brown Tiger Shrimp,Penaeus esculentus,and Western King Shrimp,Penaeus latisulcatus,Reared at Different Salinities

Abstract

Hemolymph osmolality and osmoregulatory capacity (OC) of brown tiger shrimp, Penaeus esculentus (0.94±0.04 g mean initial weight) and western king shrimp, P. latisulcatus (5.37±0.10 g mean initial weight) from four salinities (10, 22, 34 and 46 ppt) were determined following 7, 14 and 21 minutes of air-exposure. Hemolymph osmolality of both species increased with increasing salinity. Isosmotic points of brown tiger shrimp calculated from regression lines between hemolymph and medium osmolality were 30.9, 31.9, 32.1 and 31.1 ppt at 0, 7, 14, and 21 minutes of air-exposure, respectively. Isosmotic points of western king shrimp were 33.8, 33.3, 32.8 and 33.1 ppt at 0, 7, 14, and 21 minutes air-exposure, respectively. OC of brown tiger shrimp at salinity of 34 ppt did not change when exposed to air for any length whereas OC of shrimp at other salinities (10, 22 and 46 ppt) were significantly different (P < 0.05) when exposed to air for 21 minutes. OC of western king shrimp at salinity 10 ppt was reduced (P < 0.05) when exposed to 14 and 21 minutes of air when compared to control and 7 minutes of air exposure. The results indicate that both species spent less energy (P < 0.5) for osmoregulation from 30 to 34 ppt. Furthermore, salinities 10 and 46 ppt were unsuitable for rearing brown tiger shrimp and salinity 10 ppt was unsuitable for growing western king shrimp.     

土壤干旱过程对裸果木荧光特性及渗透调节物质的影响

以2年生裸果木盆栽幼苗为试验材料,在土壤干旱过程中,监测叶片荧光参数和渗透调节物质的含量,揭示裸果木幼苗对水分变化的生理响应机制,以期为裸果木抗旱机理的研究提供理论依据。结果表明,初始荧光(F_o)和非光化学猝灭(NPQ-Lss)系数随土壤水分含量的减少而持续上升;最大荧光(F_m)、原初光能潜在活性(F_v/F_o)、光化学最大量子产量(F_v/F_m)、光化学猝灭(qP-Lss)系数和稳态光量子效率(QY-Lss)随土壤水分含量的减少而呈现下降的趋势;荧光衰减率(Rfd-Lss)在土壤相对含水量达到23.23%时迅速下降。土壤水分含量减少时,叶片PSⅡ反应中心的活性降低,光合作用的原初反应过程受抑制,但叶片能通过显著提高NPQ-Lss,消耗过剩的光能来减轻干旱对光合机构的伤害。随着土壤干旱程度的逐渐加剧,脯氨酸(proline,Pro)含量显著积累,增加幅度却逐渐减小;可溶性蛋白(soluble protein,SP)含量先下降,当土壤相对含水量低于31.38%时开始显著增加;可溶性糖(soluble sugar,SS)含量持续增加。在干旱过程中,裸果木叶片能够通过积累Pro、SS和SP,来降低渗透势,起到一定的抗旱作用。     

Molecular evolution of neurohypophysial hormones in relation to osmoregulation: the two fish options

In vertebrates, water and osmolyte homeostasis is controlled by at least three hormonal systems: the hypothalamo-neurohypophysial system, the renin-angiotensin-aldosterone system and the atrial natriuretic factor system. The first system implies neuroendocrine reflexes involving an afferent neural limb from osmo- and baroreceptors to hypothalamus and an efferent endocrine limb from secretory neurons to target cell receptors and transduction to intracellular effectors, namely water and sodium channels. Evolution can affect any level of this molecular cascade. Whereas virtually all vertebrate species have two neurohypophysial hormones, an oxytocin-like and a vasopressin-like peptides, the most primitive vertebrates, Cyclostomata (lampreys and hagfishes) possess a single peptide, vasotocin, so that an early gene duplication occurred before the emergence of fishes, about 400 million years ago. The remarkable evolutionary stability of neurohypophysial hormones in bony vertebrates allows us to trace two main lineages: isotocin-mesotocin-oxytocin and vasotocin-vasopressin. In contrast, in cartilaginous fishes, the oxytocin-like peptides display a great evolutionary diversity: we have identified glumitocin in rays, aspargtocin and valitocin in the spiny dogfish, asvatocin and phasvatocin in the spotted dogfish, and oxytocin in the chimaera. Whereas bony vertebrates regulate their blood osmotic pressure (about 250–450 mOsm kg^-1 H₂O) essentially through salts, cartilaginous fishes use urea as the main osmolyte for adjusting their osmotic pressure above the external medium (about 1050 mOsm kg^-1 H₂O for marine fishes). The hypothesis is made that the stability of neurohypophysial hormones in bony vertebrates is due to their implication in ion-based osmoregulation (selective evolution), whereas in Chondrichthyes the occurrence of urea-based osmoregulation has relieved the hormones from this function and therefore made them free to vary (neutral evolution).