-->Plant Physiology and Pathology

Effects of flooding stress on growth and photosynthesis of Paeonia suffruticosa

2016/9/3 0:58:27

Growth and photosynthesis of three-year-old seedlings of Paeonia suffruticosa “fengdanbai” were investigated in a 30-day flooding experiment. Three treatment levels were set in this experiment: normal management, mild stress and severe stress levels. The results showed that after 30 d of the above three treatments accordingly, the height growth of P. suffruticosa was 3.6, 1.1 and 0.73 cm, the ground diameter growth of P. suffruticosa was 0.21, 0.11 and 0.06 cm. The increase in total plant biomass was 7.0, 3.0 and 2.75 g. The difference was remarkable between flooding stress and normal growth, the growth of P. suffruticosa was seriously affected by flooding stress. At the same time, total chlorophyll content increased under normal management, but declined under stress conditions. The root activity decreased when treated with flooding at different times. Meanwhile, under flooding stress, the transpiration rate and stomatal conductance of P. suffruticosa also decreased. Under mild flooding stress, the intercellular carbon dioxide concentration first increased and then decreased, but increased under severe flooding stress. The study suggests that flooding stress affects the P. suffruticosa root vigor, stem, leaf growth and photosynthetic characteristics. This study will provide the information for stress mechanism of jiangnan P. suffruticosa.

Effects of volatile allelochemicals from Chenopodium ambrosioides on the stoma guard cells in leaf epidermis of Vicia faba

2016/9/3 0:58:27

Chenopodium ambrosioides, an aromatic herbnative to tropical Central and South America, has become a major invasive plant in China. Allelopathy plays a crictical role in the successful invasion of C. ambrosioides, and has an allelopathic stress on neighbor plants. To explore the allelopathy mechanism, the effects of volatile oil from C. ambrosioides, α-terpinene and cymene on guard cell viabilities and nucleus morphology in Vicia faba leaves were investigated using epidermal strips bioassay, AO/EB fluorescent staining and conventional Feulgen staining. Epidermal strips of leaves were incubated in 2-(N-morpholino)ethanesulfonic acid(MES)buffer containing volatile oil, α-terpinene and cymene for 30 min at 25 ℃ in illumination incubator. The results showed that volatile oil, α-terpinene and cymene resulted in the decrease of viabilities and increase of abnormal nuclei rates in guard cell of V. faba leaves. The cytotoxicity on guard cells decreased successively from volatile oil to α- terpinene to cymene. The apoptosis features including nuclear pyknotic, malposition, stretch and degradation were observed in guard cell under the treatments of volatile oil, α-terpinene and cymene. However, the guard cell survival rates increased when strips were exposed to volatile oil, α-terpinene and cymene combined with different concentrations of a caspase inhibitor Z-VAD-FMK. These results suggested that the volatile allelochemicals from Chenopodium ambrosioides induced guard cell caspase-dependent apoptosis in Vicia faba leaves.

Effects of drought stress and allelopathy on growth, photosynthesis and physio-biochemical characteristics of Terminalia catappa seedlings

2016/9/3 0:58:27

We conducted a pot experiment with Terminalia catappa seedlings to study the impacts of drought and allelopathy on growth, photosynthesis and physio-biochemical characteristics of seedlings. In this case, we set three levels of soil moisture content(water supply range of 75%-80%, 50%-55% and 30%-35% water-holding capacity)controlled by weighing the pots with soil and seedlings and two concentration levels of leachates of Casuarina equisetifolia litter. The results showed that drought stress and litter leachates affected the survival rate and the height growth of Terminalia catappa with the seedlings growing. It significantly reduced numbers, areas, water content and biomass of leaves after 60 d dual stresses. It also significantly reduced the net photosynthesis(Pn), stomatal conductance(Ccond)and transpiration rate(Tr), but inter-cellular CO₂ concentration(Ci)decreased early and increased later. The water use efficiency(WUE)of the seedlings and the stomatal limitation value significantly increased, which might be the main reason to cause the decline of photosynthesis of seedlings. The dual stresses also increased the cell membrane penetrability and the activity of peroxidase(POD)in roots and leaves, as well as the activity of superoxide dismutase(SOD)in leaves. Analysis of variance indicated that there was interaction, which was antagonistic to certain extent, between the drought stress and allelopathy of Casuarina litter leachates on the growth, photosynthesis and physio-biochemical characteristics of Terminalia catappa seedlings. In short, this study will provide a reference for construction of mixed forest as windbreak.

Changs laws of nutrient elements, veins density, physiological index in Camellia oleifera leaves with different tree ages and their correlation with yield

2016/9/3 0:58:27

In the present research, the nutrient element, veins density and physiological index in Camellia oleifera leaves of different tree ages were compared to understand their change laws with tree age and the responding effects on yield. The results were as follows:(1)There were significant differences in the content of metal elements or rare earth elements among different ages; almost all elements showed the regularity of increasing first then decreasing with tree age while they reached the maximum content at the different ages.(2)Veins distributed in a network pattern and could be divided into three categories of great, medium and fine vein by diameter; density of great and medium vein did not change significantly while density of fine vein showed a change law of increasing first then decreasing with tree age.(3)Physiological indexes such as the content of chlorophyll, MDA, soluble sugar and soluble protein and the POD activity showed unique change laws with three ages.(4)Chlorophyll content, POD activity, total content of rare earth element and density of fine vein showed significant positive correlation with the yield(P<0.05, or P<0.01). This study will provide the reference for its cultivation and management, the parameters of nutrition, physiological and structural of the leaves can be used for tracking plant state and predicting yield.

Improved method detection Potato leafroll virus in aphids

2016/9/3 0:58:27

In the potato production, Potato leafroll virus(PLRV)can be caused enormous harm,so that the PLRV is a very important disease in potato production. RT-PCR is a commonly used method for detection of the PLRV, and the detection method is high accuracy, low cost and widely used for detection of the PLRV in potato production. But in the actual production, the samples of detection often are the infected plants, and the Myzus persicae that is the main mediator of PLRV is not detected, because of the aphid's small volume, RNA extraction of high difficulty, high cost, and that can not be rechecked extraction. For these reasons, the detection method of RT-PCR can not often be used in the potato production. In this paper, we used potato susceptible plants and viruliferous aphids as experimental materials, and used the improved method of RNA extraction from which they were extracted by PLRV RNA. Then, we made detection with PCR, and the specific primers were designed that refer of CP gene. The experimental results showed that the RNA extraction of potato susceptible plants and viruliferous aphids was integral that could be used to detect the PLRV in aphids, and it also can be used to detect the PLRV in potato susceptible plants. In addition, we used this method to detect the field of aphids and wingless aphids carrying PLRV. Wingless aphids PLRV positive rate was 100%, the positive rate of PLRV of aphids was as high as 60%, which proved that there was a good pragmatism of the practicability of the system in potato production. In this study, we used the improved efficacious method to extract RNA, and used RT-PCR to detect the PLRV in aphids. Compared with the detection of method, the new method is simple and practical, it can be used in potato production test, and it is a new means for the prevention and control of the PLRV in the potato production.

Identification of the pathogen causing black spot disease of Centella asiatica and screening of effective fungicides

2016/9/3 0:58:27

In recent years, a new disease of Centella asiatica occurred seriously in producing area of Guangxi, this pathogen usually damages the leaves and petioles, and it can lead a large area of C. asiatica to wither. It occured very common and had a long infection period on C. asiatica, so the yield and quality of C. asiatica declined seriously. We used general tissue separation to isolate from infected plants, and corroborated the pathogenicity according to Koch's Rule.; and identified the pathogen mainly based on the morphological characters and molecular analysis of internal transcribed spacer(ITS)sequences, using growth rate method, antimicrobial activity of ten fungicides assayed against the pathogen. The result showed that the pathogen Myrothecium inundatum was discovered, which resulted in black spot disease of Centella asiatica. It had strong infectiousness and occurred on healthy leaves in 24 h, and expanded rapidly to bring about the leaves wilting. The indoor antibacterial rate of the four fungicides 60% Pyraclostrobin-metiram WG, 45% Hymexazol-metalaxyl WP, 1.8% Xinjunan acetate AS and 80% Mancozeb WP were above 98%, they had strong antimicrobial effects. The relevant references indicated that Myrothecium inundatum the four fungicides could take turns to control this disease in field. The indoor antibacterial rate of these three fungicides 15% Prochloraz ME, 70%Thiophanatemethyl WP and 10%Kresoxim-methyl SC were above 92%, the antimicrobial effects of them were also satisfied. Therefore, we can consider to use these three fungicides in production properly.