Combining Ability Analyses of Net Photosynthesis Rate in Pepper (Capsicum annuum L.)

In perspective of breeding high-yield hybrid pepper varieties, combining ability analysis of net photosynthesis rate at different phases of flowering and fruit setting in pepper was made with 15 cross combinations from 6 parents by （1/2） n （n- 1） diallel crosses. There are relatively large differences not only in general combining ability （GCA） effect among different parents and at different phases of flowering and fruit setting, but also in specific combining ability （SCA） effect among different hybrids. There are relatively large GCA effects in late parents but relatively less GCA effects in early parents. No obvious laws have been found in the relationship between SCA effects and maturity of hybrids. Variances of SCA are larger than those of GCA. Heritability is less but influence of environment is larger. Correlation analysis of combining ability between net photosynthesis rate and agronomic character or resistances to main diseases has showed that correlation coefficients of GCA are relatively large at the medium phase and the late phase of flowering and fruit setting. Net photosynthesis rate is more relative to leaf characters and fruit characters. Correlation coefficients of SCA are relatively large at the early phase and the late phase of flowering and fruit setting. Net photosynthesis rate is more relative to leaf characters and plant characters at the early phase but to plant characters and fruit characters at the late phase. Correlation coefficients of SCA between net photosynthesis rate and resistances to main diseases are larger than those of GCA. The combining abilities of net photosynthesis rate at different phases of flowering and fruit setting are positively correlated with those of yield per plant. The combining ability is an important parameter of breeding of high photosynthesis hybrid pepper varieties.

SIMPLE SIMULATION OF THE ANNUAL VARIATION OF THE SPECIFIC PHOTOSYNTHESIS RATE IN JIAOZHOU BAY

A simple diagnostic simulation of the annual cycling of the surface specific photosynthesis rate (SPR) in Jiaozhou Bay is described in this paper. Light intensity, temperature and nutrients (nitrate + ammonia, phosphate) were considered as main factors controlling photosynthesis of phytoplankton and were introduced into the model by different function equations. The simulated variation of specific photosynthesis rate coincided with the measured data. Analysis of the effect of every factor on photosynthesis indicated that the variation of photosynthesis rate was controlled by all these three factors, while temperature showed good correlation with SPR as measurement showed. This diagnostic simulation yielded the values of some parameter relating with the photosynthesis in Jiaozhou Bay.

Effects of Paclobutrazol Seed Priming on Seedlings Quality,Physiological and Bakanae Disease Index Characteristics of Rice(Oryza sativa L.)

Rice(Oryza sativa L.)is one of the most important cereal crops in the world.Bakanae disease is a significant rice disease widely distributed in rice-growing regions worldwide.Therefore,the present investigation aimed to assess the optimal concentrations of paclobutrazol(PBZ)as a treatment for rice grains(cv.Sakha 108)to control bakanae disease,also evaluating its impact on grain germination,seedling growth parameters as well as disease index.Paclobutrazol concentrations had no significant impact on seed germination,regardless of whether the seeds were incubated with Fusarium fujikuroi or not.Application of PBZ,either alone or in combination with fungal pathogens,negatively impacted the rice seedlings’height.Paclobutrazol at 25,50 and 100 mg/L,combined with the fungal pathogen positively impacted root length.Paclobutrazol at 3 and 6 mg/L mitigated the adverse impact on chlorophyll pigments content in infected seedlings.The highest proline contents were achieved by 100 mg/L PBZ alone or in combination with fungal pathogens.It has been observed that the application of PBZ,either alone or in combination with a fungal pathogen,leads to the enhancement of catalase,peroxidase,and polyphenol oxidase activities.The median lethal concentration of PBZ was 0.874 mg/L;applying low concentrations of paclobutrazol effectively increased the percentage of fungal growth suppression.Application of PBZ,at higher concentrations(50 and 100 mg/L),decreased infection percentage and disease severity index(DSI)significantly.These findings suggest that PBZ can be an effective treatment for controlling bakanae disease and enhancing resistance in rice plants.

Photosynthesis and Transpiration Characters of Alfalfa (Medicago sativa) and Their Relationship with Relevant Factors during Branching Stage

[ Objective] The paper presents the diumal changes of photosynthesis and transpiration of different alfalfa varieties and their relationship with the associated physiological and ecological factors during branching stage, so as to provide a basis for the development, utilization, and breed- ing of alfalfa. [ Method] Under natural conditions, the diurnal changes of net photosynthetic rate （Pn）, transpiration rate （Tr）, the relevant physio- logical factors including leaf temperature （TI）, stomatal conductance （Gs） and intemal COn concentration （Ci）, as well as the relevant physiologi- cal factors including photosynthetic available radiation （PAR）, CO2 concentration in field （Ca） and air temperature （Ta） were measured in four al- falfa varieties （Algonguin, WL323 HQ, WL414, and Millionaire）. The water use efficiency （WUE） and light use efficiency （LUE） were calculated, and the correlation among them was also analyzed. [Result] The Pn, Tr, PAR and Ta of the four varieties appeared to vary in a single-peak curve; the sequence of WUE was WL323 HQ ~ Algonguin ~ WL414 ~ Millionaire; there was no significant difference in LUE of the four alfalfa varieties; coef- ficient analysis showed that Pn was mainly affected by PAR, Gs, and Ci, while Tr by PAR and Ta. [ Conclusion] WL323 HQ is the variety with high Pn, high WUE and low Tr, and it has strong adaptability to drought. In four alfalfa varieties, PAR, Ta, Gs, and TI are the primary determining fac- tors while Ca and Ci the limiting factors of Tr; Gs is the primary determining factor while Ci the limiting factor of Pn.

Photosynthesis,Metabolite Composition and Anatomical Structure of Oryza sativa and Two Wild Relatives,O.grandiglumis and O.alta

Photosynthesis, enzyme activities and metabolite pools associated with primary carbon metabolism in leaves were studied in O. grandiglumis and O. alta （wild relatives of rice which produce high biomass） versus O. sativa （a japonica cultivar and a indica-japonica hybrid） to assess their potential for identifying traits which might be utilized to enhance rice productivity. The wild relatives had higher rates of photosynthesis on a fresh weight basis, and higher water use efficiency than the O. sativa lines. There were no striking differences in activities of a number of key enzymes in carbon and nitrogen metabolism between the wild relatives and cultivated rice lines. Along with higher rates of photosynthesis on a fresh weight basis, the leaves of the two wild species had higher nitrate content, higher levels of starch, glucose and fructose, and higher levels of organic acids （malate, succinate and acetate）, compared to the O. sativa lines. The results suggested that O. grandiglumis and O. alta have differences in physiology and primary metabolism which might be exploited to improve growth and productivity of cultivated rice.

CO_2, H_2O exchange and stomatal regulation of regenerated Camptotheca acuminata plantlets during ex vitro acclimatization

For finding the changes in CO2, H20 exchange and their stomatal regulation during ex vitro acclimatization of regenerated Camptotheca acuminata plantlets, the net photosynthesis rate （Pn）, respiration rate （Ro）, light compensation point （Lc） and light saturation point （Ls）, transpiration rate （Tr）, stomatal conductance （gs） and water use efficiency（WUE） were measured during 37 days of ex vitro acclimatization. The results showed that Pn sharply increased until 29 days, then slightly decreased. A substantial decrease in Lc and a substantial increase of Ls in the former two weeks were observed, indicating the light regime enlargement for effective leaf photosynthesis. Tr and gs abruptly decreased during the first week then linearly increased until 29days ex vitro acclimatization, reflecting the strong regulation effect of stomata on water changes of ex vitro acclimating plantlets. Stomatal regulation effect on CO2 exchange was different from that on water exchange, i.e. P, was almost independent of gs during the first week, while P. was significantly correlated with gs thereafter （i.e. dual patterns）. Different from dual patterns of gs-Pn relation, the Tr monotonously linearly increased with gs. Furthermore, WUE was almost independent on gs during the first week, while a marked decreasing tendency with gs was found thereafter. At the beginning of the acclimatization, WUE was mainly determined by photosynthetic capacity, while transpiration becomes a main determinant factor for WUE from 7 to 37 days＇ acclimatization.

Ecophysiology and multivariate analysis for production of Tachigali vulgaris in Brazil:Influence of rainfall seasonality and fertilization

Studies on fertilization management of species native to the Amazon for energy plantations contribute to the diversity of species use and reduce biological risk due to the excessive use of clones or hybrids of Eucalyptus.This study evaluates the effect of precipitation seasonality and phosphorus and potassium fertilization on gas exchange in a Tachigali vulgaris plantation.Three levels of P(zero,65.2,130.4 kg ha^(-1))and three of K(zero,100.0,200.0 kg ha^(-1))were applied in a 3×3 factorial randomized block design.Gas exchange measurements were conducted in April and November 2018.In low rainfall,high irradiance period,photo synthetic rates were up to four times higher than in the high rainfall period,reaching 20.3μmol m^(-2)s^(-1)in the treatment with 130.4 g kg^(-1)of P and 100.0 g kg^(-1)of K.Factor analysis and principal component analysis reduced the initial eight gas exchange variables to two and three principal components in periods of high and low rainfall,respectively.The multivariate method used in this study readily identified variations in the variables as a function of rainfall,with high reliability in explaining the data set.

Adaptive responses of Acer ginnala, Pyrus ussuriensis and Prunus davidiana seedlings to soil moisture stress

One-year-old seedlings of Amur maple (Acer ginnala Maxim), Ussurian pear (Pyrus ussuriensis Maxim) and David peach (Prunus davidiana Carr) were planted in pots in greenhouse and treated with four different soil moisture contents (75.0%, 61.1%, 46.4% and 35.4%). The results showed that net photosynthesis rate (NPR), transpiration rate (TR) and stomatal conductance (Sc) of seedlings of the three species decreased with the decease of soil moisture content, and Amur maple seedlings had the greatest change in those physiological indices, followed by Ussurian pear, David peach. Amur maple and Ussurian pear seedlings also presented a decrease tendency in water use efficiency (WUE) under lower soil moisture content, whereas this was reversed for David peach. Under water stress the biomass allocation to seedling root had a significant increase for all the experimental species. As to root/shoot ratio, Amur maple seedlings had the biggest increase, while David peach had the smallest increase. The leaf plasticity of Amur maple seedlings was greater, the leaf size and total leaf area decreased significantly as the stress was intensified. No significant change of leaf size and total leaf area was found in seedlings of Ussurian pear and David peach. It was concluded that Amur maple was more tolerant to soil moisture stress in comparison with David peach and Ussurian pear.

Study on Photosynthetic Characteristics of a Rice CMS Line Renong 1A with Yellow-green Revertible Leaves

[Objective] Understanding the photosynthetic characteristics of the rice CMS line Renong 1A with leaf color markers can promote its utilization in breeding. [Method] The wild type （WT） of rice spontaneous mutant with virescent-yellow leaves that was the male parent of Renong 1A was selected as the control, and the contents of photosynthetic pigments, photosynthetic parameters, light-response curve and chlorophyll fluorescence kinetic parameters of Renong 1A were measured at the tillering stage. [Result] New leaves of Renong 1A yellowed obviously in the early period. Chlorophyll content, photosynthetic rate and values of parameters Pdt, F/Fm Fv＇/Fm＇,φPSII, and ETR of Renong 1A were all significantly lower than those of the control. However, there was no difference between Renong 1A and the control in terms of photosynthetic rate of leaves turning green. [Conclusion] The photosynthetic capacity of new leaves of Renong 1A decreased at the early stage due to the reduction of chlorophyll content, and then it became normal at the later stage with the increase of chlorophyll content.

Isolation and physiological characteristics of a premature senescence mutant in rice(Oryza sativa L.)

A rice pse（t） （premature senescence, tentatively） mutant line, was isolated from 4500 independent T-DNA inserted transgenic lines. The symptoms of premature senescence appeared more severely than those of the control plants （Zhonghua 11, japonica） at the last development stage. To characterize the mutant and provide basic information on the candidate genes by mapping to a physical region of 220-kb, experiments were carried out in two phytotrons under controlled temperature of 24 ℃ and 28 ℃, respectively. The content of chlorophyll, soluble protein and MDA （malondialdehyde）, net photosynthesis, the antioxidant enzyme activities of SOD （superoxide dismuase） （EC 1.15.1.1 ） and POD （peroxidase） （EC 1.11.1.7） and the peptidase activities of leaves were measured from top to bottom according to the leaf positions at the flowering stage. Compared with the control plant, the mutant showed the following characteristics： （1） Higher net photosynthesis rate （Pn） appeared in the 1st and 2nd leaves, contents of chlorophyll and soluble protein were also higher in the 1st leaf; （2） The activities of SOD, POD and peptidase were higher according to the leaf position from top to bottom; （3） The symptom of premature senescence was accelerated in the mutant at 28 ℃ treatment. The MDA content and the SOD and POD activities between the 24 ℃ and 28 ℃ treatment mutants were not significantly different. Content of chlorophyll and soluble protein of leaves mutant decreased rapidly at 28 ℃ treatment. The results show thatpse（t） is sensitive to high temperature. The probable function of PSE（T） is discussed.

Comparative study of responses in the brown algae Sargassum thunbergii to zinc and cadmium stress

Heavy metal pollution in aquatic system is becoming a serious problem worldwide. In this study, responses of Sargassum thunbergii to dif ferent concentrations(0, 0.1, 0.5, 1.0 and 5.0 mg/L) of zinc(Zn) and cadmium(Cd) exposure separately were studied for 15 days in laboratory-controlled conditions. The results show that the specifi c growth rates increased slightly under the lower Zn concentration treatment(0.1 mg/L) at the first 5 d and then decreased gradually, which were significantly reduced with the exposure time in higher Zn concentrations and all Cd treatments compared to respective control, especially for 1.0 and 5.0 mg/L Cd. Chlorophyll a contents showed significant increase in 0.1 mg/L Zn treatment, whereas the gradually reduction were observed in the other three Zn treatments and all Cd treatments. The oxygen evolution rate and respiration rate presented distinct behavior in the Zn-treated samples, but both declined steadily with the exposure time in Cd treatments. The P/R value analyses showed similar variation patterns as chlorophyll a contents. Real-time PCR showed that lower Zn concentration(0.1 mg/L) increased mRNA expression of rbcL gene, whereas higher Zn concentrations and Cd reduced the rbcL expression. Taken together, these findings strongly indicate that Zn and Cd had different effects on S. thunbergii both at the physiological and gene transcription levels, the transcript level of photosynthesis-related gene rbcL can be used as an useful molecular marker of algal growth and environment impacts.

Studies on photoprotective mechanism of desert plant Reaumuria soongorica under progressive soil drying

Reaumuria soongorica （pall.） Maxim, a perennial desert semi-shrub, is widely found in semi-arid areas of China. It shows strong tolerance to drought, high temperature and intense radiation in its natural habitat. In the present study, photoprotective mechanism of R. soongorica was investigated by analyzing diurnal variations of gas exchange and chlorophyll fluorecence parameters during progressive soil drying. The results show that leaf water potential of R. soongorica decreased when the soil water content dropped. Diurnal patterns of net photosynthetic rate （Pn） changed from ＂two peaks＂ to ＂one peak＂ under drought stress, and the leaf water use efficiency （WUE） increased under moderate drought and declined under severe drought. Pn , the primary maximum photochemical efficiency of PSII （Fv/Fm） and the quantum efficiency of non-cyclic electron transport of PSII （ΦPSII） decreased obviously at noon, and showed a photoinhibition phenomenon. But, the non-photochemical quenching of fluorescence （NPQ） soon reached its maximum in the day and then remained almost at the high level until 17：00, indicating that the xanthophylls cycle-dependent thermal energy dissipation played an important role. Diurnal variations of the original chlorophyll fluorescence （Fo） increased at first and then decreased. The increased value of F o under drought stress indicates that there was a reversible inactivation of PSII reaction center. These results indicate that the photoprotective mechanism in R. soongorica was the photoinhibition by using both the xanthophylls cycle-dependent thermal energy dissipation and the reversible inactivation of PSII reaction center under drought stress.