Leaf Photosynthesis in Response to Removing Fruit During Different Phenological Stages of Fruit Development in Peach Trees

Removing fruit (RF) and retaining fruit (CK) were carried out during different phenological stages of fruit development onone-year-old shoot of Okubo peach trees [Prunus persica (L.) Batsch.] under preventing exportation of the assimilates tothe non experimental parts of the tree by girdling one-year-old shoot and keeping the same leaves between RF and CK.The results showed that fruit removal significantly decreased net photosynthetic rate (Pn), stomatal conductance (Gs)and transpiration rate (E), but significantly increased leaf surface temperature (TLeaf ) at about midday as compared with CK.Internal CO2 concentration, soluble sugar content, reductive sugar content, starch content except that during the finalrapid fruit growth stage, ADP-glucose pyrophosphorylase and amylase activities in source leaves were not significantlyaffected by fruit removal. There was a significantly positive parabolic correlation between Pn and Gs, and a strongpositive linear correlation between Pn and E. Moreover, Pn increased with increased TLeaf if TLeaf was below 38°C, thendecreased sharply when TLeaf exceeded the above critical temperature for both RF and CK. Pn of RF was lower, however,than that of CK in the same TLeaf , especially if TLeaf exceeded 38°C. It is suggested that the decreased stomatal aperture andincreased TLeaf may be the important mechanism in regulating photosynthesis under a decreased strength of sink demandby RF in fruit trees.

Seed priming improves early seedling vigor, growth and productivity of spring maize

Potential of seed priming treatments in improving the performance of early planted maize was evaluated against timely planting. Seeds of maize hybrid FH-810 were soaked in water (hydropriming), CaCl2 (2.2%, osmopriming), moringa leaf extracts (MLE 3.3%, osmopriming) and salicylic acid (SA, 50 mg L–1, hormonal priming) each for 18 h. Untreated and hydroprimed seeds were taken as control. Seeds primed with SA took less time in emergence and had high vigor in early planted maize. Amongst treatments, hormonal priming, reduced the electrical conductivity, increased the leaf relative and chlorophyl contents fol owed by osmopriming with CaCl2 at seedling stage. Likewise, plant height, grain rows and 1 000-grain weight, grain and biological yield and harvest index were also improved by seed priming;however hormonal priming and osmopriming with MLE were more effective in this regard. Improved yield performance by hormonal priming or osmopriming with MLE in early planting primarily owed to increased leaf area index, crop growth and net assimilation rates, and maintenance of green leaf area at maturity. In conclusion, osmopriming with MLE and hormonal priming with SA were the most economical treatments in improving productivity of early planted spring maize through stimulation of early seedling growth at low temperature.

Bionic Leaf Simulating the Thermal Effect of Natural Leaf Transpiration

We proposed a kind of bionic leaf to simulate the thermal effect of leaf transpiration. The bionic leaf was firstly designed to be composed of a green coating, a water holding layer, a Composite Adsorbent （CS） layer and an adsorption-desorption rate controlling layer. A thermophysical model was established for the bionic leaf, and the dynamic simulation results reveal that the water holding layer is not necessary; a CS of high thermal conductivity should be selected as the CS layer; the adsorp- tion-desorption rate controlling layer could be removed due to the low adsorption-desorption rate of the CS; and when CaC12 mass fraction of the CS reaches 40%; the bionic leaf could simulate the dynamic thermal behavior of the natural leaf. Based on the simulation results, we prepared bionic leaves with different CaC12 content. The thermographies of the bionic leaf and the natural leaf were shot using the Infrared Thermal Imager. The measured average radiative temperature difference between the bionic and natural leaves is less than 1.0 ℃.

The Heat and Mass Transfer Analysis of a Leaf

Understanding the heat and mass transfer processes of plant leaves is essential for plant bionic engineering. A general thermophysical model was established for a plant leaf with particular emphasis on the transpiration process. The model was verified by the field measured stomatal resistance and temperature of a camphor leaf. A dynamical simulation revealed that diurnal transpiration water consumption is dominated by the solar irradiance and the day-average temperature of the leaf is dominated by the ambient air temperature; transpiration plays an important role in the cooling of the leaf, in average it could dissipate around 32.9% of the total solar energy absorbed by the leaf in summer. To imitate the thermal infared characteristic of the real leaf, the up surface of the bionic leaf must have emissivity and solar absorptivity close to those of a real leaf and its shape and surface roughness must be similar to those of the real leaf. The key point is that the bionic leaf must be able to evaporate water to simulate the transpiration of a plant leaf, appropriate adsorbent can be used to realize this function.

Non-invasive water status detection in grapevine(Vitis vinifera L.)by thermography

Grapevines are preferentially grown under mild to moderate water stress conditions to achieve the best compromise between wine quality and quantity.Water status detection for advanced irrigation scheduling is frequently done by predawn leaf water potential(ΨPD)or leaf stomata conductance(gL)measurements.However,these measurements are time and labor consuming.Therefore,the use of infrared thermography(IRT)opens up the possibility to study large population of leaves and to give an overview on the stomatal variation and their dynamics.In the present study IRT was used to identify water stress of potted grapevines.In order to define the sensitivity of IRT measurements to water stress,the IRT-based water status information were compared with simultaneously measuredΨPD and gL data.Correlations between IRT-based CWSI data on the one hand and gL andΨPD on the other showed the potential of IRT for water stress detection.However,the CWSI calculation procedure is laborious and the sensitivity of CWSI for water stress detection still needs to be improved.Therefore,further improvements are necessary in order to apply remote IRT-based systems for irrigation scheduling in the field.