Effect Of Dissolved Oxygen Concentration And Its Internal Transportation On Phyllostachys Violascens Growth

Phyllostachys violascens is one of the important bamboo species for bamboo shoots in China.Because the mulching technology can make it shoot ahead of time to around the Spring Festival,it greatly improves the economic benefits,and thus the mulching technology is widely applied in production.However,under mulching conditions,the blocking of the mulch affects the normal gas exchange on the soil surface,which reduces the soil oxygen concentration.This may be one of the reasons for the poor growth of P.violascens and the decline in the production of P.violascens.In order to certain the demand of oxygen for the growth of P.violascens,three experiments were carried out in this paper: Firstly,under hydroponic conditions,the hydroponic P.violascens seedlings(without rhizomes)were used as the material to research about the effect of different dissolved oxygen concentrations on the growth of hydroponic P.violascens seedlings;the second,potted P.violascens seedlings(with rhizomes)were used as material to research about the physiological response of P.violascens to different dissolved oxygen concentrations under flooding conditions;the third,Phyllostaehys heteroelada oliver,P.violascens,Phragmites and Phyllostachys pubescens were used as materials,the tissue ventilation and morphological structure of different parts of them were compared to clarify the oxygen demand of P.violascens and the structure of the oxygen pathway inside of P.violascens,revealing the internal mechanism of P.violascens’ s intolerance to hypoxia.The main findings are as follows: 1.With the increasing of dissolved oxygen concentration in the nutrient solution,the biomass accumulation,leaf area,root activity,antioxidant enzyme activity and photosynthetic pigment content of hydroponic Phyllostachys violascens seedlings gradually increased.Under hydroponic conditions,8 mg·L-1 was the optimal dissolved oxygen concentration for the growth of hydroponic seedlings.However,the growth of hydroponic seedlings grown under saturated dissolved oxygen was still not as good as that of Phyllostachys violascens seedlings which grown in the soil.Under hydroponic conditions,the formation of lysigenous aerenchyma in the root of hydroponic Phyllostachys violascens seedlings was observed,indicating that Phyllostachys violascens adapts to the anoxic hydroponic environment by changing its own tissue morphology.2.Potted Phyllostachys violascens seedlings with obvious rhizome were not resistant to flooding.They would die after long-term flooding,but higher dissolved oxygen concentration could prolong their survival time.After flooding,the leaves of potted Phyllostachys violascens seedlings would gradually wither and turn yellow and fall off.The shortest could survive for 39 days and the longest could survive for 56 days.3.The tissue ventilation of all parts of Phyllostachys violascens was significantly lower than that of Phyllostaehys heteroelada oliver and Phragmites(P <0.05).The minimum ventilating pressures at the junction of shoot-rhizome of Phyllostachys violascens was 0.2Mpa,which was significantly higher than that of Phyllostaehys heteroelada oliver and Phragmites(P <0.05),indicating that the junction of shoot-rhizome limited the oxygen transportation of shoot and rhizome.4.The cavity at the base of Phyllostachys violascens stems disappeared,only a large number of vascular bundles were densely distributed.The lack of ventilation pathways observed inside of Phyllostaehys heteroelada oliver and Phragmites caused the porosity of the junction of shootrhizome of Phyllostachys violascens to be significantly lower than that of Phyllostaehys heteroelada oliver and Phragmites.