Effect of Seedling Raising Methods on Leaf Photosynthesis and Grain Yield of Mechanically-transplanted Japonica Rice

This study was conducted to investigate the effects of seedling raising modes on photosynthetic charactedsticsand grain yield under wheat straw returning. Four representative cultivars in Huaibei area were selected as test materials. By setting potted seedlings and carpet seedlings, the effects of different nursery meth- ods on the photosynthesis of rice at different growth stages in Huaibei area were investigated. Compared with carpet seedlings, the leaf area index of potted seedlings decreased at the maturation stage, but the dry weight of leaf shewed no significant difference.The SPAD of potted seedlings had an increasing trend after transplanting, but the SPAD increased differently according to cultivars. The net photosynthetic rate, stomatal conductance and transpiration rate of the leaves of pot seeding rice were significantly higher than those of carpet seedling rice on the 85^th d after transplanting. However, theintracellular CO2 concentration and water use efficiency of leaves had no significant differences between different ＇treatments. The results indicate that the photosynthetic capacity of flag leaves of pot seedling rice is stronger in early and middle stages, but the decay rate of photosynthetic function is slightly faster than carpet seedling rice, which might be the main reason for the rice yield of potted seedlings having no remarkable difference from carpet seedlings.

Effects of biofertilizer and water-saving irrigation interactions on the leaf photosynthesis and plant growth of tomatoes

Irrigation and fertilizer interaction is an efficient cultivation management strategy for facility agriculture.However,the effects of irrigation and fertilizer management on tomato growth and its physiological factors remain unclarified.In this study,two irrigation patterns(W1,conventional irrigation;W2,water-saving irrigation)and four fertilizer application patterns(CF,chemical fertilizer;BOF,biological organic fertilizer;NPK,nutrient compound fertilizer;BOF+NPK)were selected to observe the effects of their interaction on cherry tomato plant growth,leaf photosynthesis and fruit quality through pot experiments.The results showed that W2 treatments promoted plant height growth compared to W1 under the same fertilizer addition.Moreover,irrigation and fertilizer management had significant effects on net photosynthetic rate,intercellular oxidation concentration,stomatal conductance and transpiration rate at the first sequence flowering and fruiting stages.The maximum tomato plant height(99.0 cm)was achieved under the irrigation and fertilizer pattern of BOF and W2,along with the highest fruit yield of 1.98 kg/plant,which was approximately 31.1%higher than the minimum yield under the combined CF and W2 treatment.Under W2 treatments,the application of either NPK or BOF increased the soluble sugar content of tomatoes.The structural equation models showed that the soil alkali hydrolyzed nitrogen could directly significantly affect the yield and soluble sugar.The findings suggest that optimization of irrigation-fertilizer interactions positively regulates tomato growth,providing an efficient model for tomato irrigation and fertilizer management and a reference for sustainable development of facility agriculture.

Leaf Turgor Potential, Plant Growth and Photosynthesis in Organically Fertilized Sweet Corn

A greenhouse pot experiment was conducted using a complete random design with six replications. A pressure-volume curve analysis was employed to study the effects of organic fertilizers on plant water relations in sweet corn (Zea mays L. cv. Honey-bantam) in terms of leaf osmotic concentration (Cs), osmotic potentials at full turgid status (πFT) and at incipient plasmolysis (πIP), and of symplastic (ζsym) and apoplastic (ζapo) fractions in the tissue water compartment in relation to photosynthetic capacity (Pc) and dry mass accumulation. At the seedling stage (day 15), plants with chemical fertilizer treatments showed lower πFT, πIP and ζapo and higher Cs, ζsym and PC than those with organic fertilizer treatments. Compared to PC and relative growth, where values from day 15 to day 75 were first lower for organic treatments and then higher, ζsym and Cs values were similar, while πFT and πIP were opposite being higher then lower. Dry mass production with organic fertilizer was higher than or close to the chemical fertilizer treatments in the later growth stage (day 75), though dry mass production with chemical fertilizers was much higher in the early and middle growing stages (days 15 and 45). Increased photosynthesis and dry mass production in later growth stages due to organic fertilizers were associated with increased osmotic concentration in the tissue and the symplastic fraction of the tissue water compartment. These might favor stomatal opening and biochemical activities.

Varietal difference in the correlation between leaf nitrogen content and photosynthesis in rice(Oryza sativa L.) plants is related to specific leaf weight

Increasing leaf photosynthesis per area（A） is of great importance to achieve yield further improvement. The aim of this study was to exploit varietal difference in A and its correlation with specific leaf weight（SLW）. Twelve rice cultivars, including 6 indica and 6 japonica varieties, were pot-grown under two N treatments, low N（LN） and sufficient N（SN）. Leaf photosynthesis and related parameters were measured at tillering stage. Compared with LN treatment, A, stomatal conductance（g_s）, mesophyll conductance（g_m）, leaf N content（N_（area））, and chlorophyll content were significantly improved under SN treatment, while SLW and photosynthetic N use efficiency（PNUE） were generally decreased. Varietal difference in A was positively related to both g_s and g_m, but not related to N_（area）. This resulted in a low PNUE in high N_（area） leaves. Varietal difference in PNUE was generally negatively related to SLW. Response of PNUE to N supply varied among different rice cultivars, and interestingly, the decrease in PNUE under SN was negatively related to the decrease in SLW. With a higher N_（area）, japonica rice cultivars did not show a higher A than indica rice cultivars because of possession of high-SLW leaves. Therefore, varietal difference in A was not related to N_（area）, and SLW can substantially interfere with the correlation between A and N_（area）. These findings may provide useful information for rice breeders to maximize A and PNUE, rather than over reliance on N_（area） as an indicator of photosynthetic performance.

Effect of precipitation condition on photosynthesis and biomass accumulation and referring to splash erosion status in five typical evergreen tree species in humid monsoon climatic region of subtropical hill-land

Negative effect of precipitation on plant photosynthesis was investigated in this work. Stomatal conductance, transpiration rate and net photosynthetic rate were measured before and after each precipitation event, respectively, and the corresponding precipitation was recorded as well. Moreover, plant dry matter accumulation was counted at the end of our entire experiment. The results show that precipitation fully demonstrates its negative effect on plant photosynthesis under the condition of without water shortage. Although it has not been proved, leaf shape seems to be associated with this effect. Broad-leaved species are less influenced than coniferous and lanceleaf species no matter on the length of variation time or changes in variation values. The different situation among three broad-leaved species seems to illustrate that the effect is also related to the size of single leaf area. The correlation between precipitation and photosynthetic rate variation is analogous to the relationship between precipitation and splash erosion, and in the view of the relationship between plant photosynthetic characteristics and dry mass accumulation, it can be thought that it can reflect the negative impact of precipitation on plant growth by making use of splash erosion. Therefore, a section was added in the traditional plant biomass estimation algorithms by using eco-physiological models, and this was proved to enhance the accuracy of traditional estimation from preliminary verifications.

Effects of Irrigation Schedules on Photosynthetic Carbon Assimilation of Winter Wheat (Triticum aestivum L.) in North China Plain:from Leaf to Population

A field experiment was conducted to elucidate the regulation mechanism of different irrigation schedules on population photosynthetic of winter wheat. The experiment included five irrigation schedules, such as no irrigation （W0）, irrigation once at jointing （W1j） or at booting （W1b）, irrigation twice at jointing and booting （W2）, and irrigation three times at jointing, booting and grain-filling （W3） and three planting densities, such as 180 （D1）, 300 （D2） and 450 （D3） seedlings per square meter. The results indicated that irrigation significantly improved population photosynthesis. The relationship between population photosynthesis and irrigation time/volume was to some extent parabolic. Improvements in population photosynthesis （resulting from more irrigation time/volume） were mainly related to increase in leaf area index and population light interception. Population photosynthesis exhibited a significantly negative correlation with canopy light transmittance. Population photosynthesis at grain filling stage was significantly positively correlated with dry matter accumulation at post-anthesis and grain yield. Main effects and partial correlation analysis showed that population photosynthesis of W0, W1j, W1b and W3 were regulated by canopy light transmittance and leaf area. On the other hand, population photosynthesis of W2 was mainly influenced by flag leaf photosynthetic rate. On this basis, planting 300 seedlings per square meter was the optimum combination. The combination of W2D2 increased population photosynthesis during mid-late growth stages and extended high population photosynthesis duration, which ultimately increased grain yield.

Agronomic and physiological traits associated with genetic improvement of phosphorus use efficiency of wheat grown in a purple lithomorphic soil

Developing wheat that acquires and uses phosphorus(P)more efficiently is a promising and low-cost solution for increasing grain yield and reducing P-related environmental impacts.The present study identified agronomic and physiological traits that contribute to genetic variation in the P acquisition,remobilization,and utilization efficiency of 11 wheat cultivars from southwest China grown in P-deficient purple lithomorphic soil(Olsen P=4.7)with balanced(75 kg P ha^(−1))and excess P(120 kg P ha^(−1))supplies.On average,soil P deficiency(–P)reduced root P uptake(17.0%–60.8%),P remobilization(33.9%–52.8%),dry mass yield(11.5%–39.2%),and grain yield(17.7%–54.4%).Balanced P(+P)increased grain yield via increased plant biomass rather than increased HI.–P increased phosphorus uptake efficiency(PUpE,4.5-fold),phosphorus utilization efficiency(PUtE,1.25-fold),and phosphorus use efficiency(PUE,5.4-fold)compared with those under+P,and PUtE explained most(58.1%–60.8%)of the genetic variation in PUE under both–P and+P.The high root P uptake of P-efficient cultivars under–P was regulated by root surface area and root length density in the 0–10 cm soil layer but not in the 10–20 and 20–40 cm soil layers,suggesting that a topsoil foraging strategy is a more economical approach than deeper root exploration for increasing P uptake.Root P uptake before anthesis and P remobilization after anthesis were critical for increasing the PUtE of wheat,given that P-efficient cultivars showed higher Pn(net photosynthetic rate)and sucrose levels than P-inefficient cultivars.Pn reduction by–P resulted from decreased Gs and Ci,and high evapotranspiration under+P increased shoot P%by increasing root P uptake.Genetic variation in the source-to-sink ratio was observed in consequence of a+P-induced allometric increase in sucrose in leaves and kernels.Owing to these beneficial effects,+P increased the kernel N and P yields of the 11 cultivars by 9.9%–52.4%and 12.3%–48.8%,respectively.The findings of this study could help improve wheat in future breeding efforts and P management by identifying desirable Pefficient phenotypes in P-deficient farming systems.

The effect of artificial solar spectrum on growth of cucumber and lettuce under controlled environment

Light-emitting diodes(LEDs)have been widely applied in the controlled environment agriculture,which are characterized by relatively narrow-band spectra and energetical efficiency.Most recently,the spectrum of Sunlike LEDs has been engineered and it closely resembles solar spectrum in the range of photosynthetic active radiation(PAR,400–700 nm).To investigate how plant growth responses to the spectrum of Sunlike LEDs,cucumber and lettuce plants were cultivated and their responses were compared with the conventional white LEDs as well as composite of red and blue LEDs(RB,R/B ratio was 9:1).We observed that although Sunlike LEDs resulted in a longer stem in cucumber,dry weight and leaf area were similar as those under RB LEDs,and significantly higher than those under white LEDs.Moreover,cucumber leaves grown under Sunlike and white LEDs showed higher photosynthetic capacity than those grown under RB LEDs.For lettuce,plants grown under Sunlike LEDs showed larger leaf area and higher dry weight than the other two treatments.However,the leaf photosynthetic capacity of lettuce grown under Sunlike LEDs was the lowest.In this context,the spectrum induced plant functions are species-dependent.Furthermore,the three types of LEDs show distinct light spectra and they are different in many aspects.Therefore,it is difficult to attribute the different plant responses to certain specific light spectra.We conclude that plants grown under Sunlike LEDs exhibit larger leaf area,which may be due to some specific spectrum distributions(such as more far-red radiation),and consequently are favorable for light interception and therefore result in greater production.