The maximum carboxylation rate of Rubisco (V_cmax) and maximum rate of electron transport (Jmax) for the biochemical photosynthetic model, and the slope (m) of the Ball-Berry stomatal conductance model influence gas exchange estimates between plants and the atmosphere.  However, there is limited data on the variation of these three parameters for annual crops under different environmental conditions.  Gas exchange measurements of light and CO₂ response curves on leaves of winter wheat and spring wheat were conducted during the wheat growing season under different environmental conditions.  There were no significant differences for V_cmax, J_max or m between the two wheat types.  The seasonal variation of V_cmax, Jmax and m for spring wheat was not pronounced, except a rapid decrease for V_cmax and J_max at the end of growing season.  V_cmax and J_max show no significant changes during soil drying until light saturated stomatal conductance (g_ssat) was smaller than 0.15 mol m^–2 s^–1.  Meanwhile, there was a significant difference in m during two different water supply conditions separated  by g_ssat at 0.15 mol m^–2 s^–1.  Furthermore, the misestimation of V_cmax and Jmax had great impacts on the net photosynthesis rate simulation, whereas, the underestimation of m resulted in underestimated stomatal conductance and transpiration rate and an overestimation of water use efficiency.  Our work demonstrates that the impact of severe environmental conditions and specific growing stages on the variation of key model parameters should be taken into account for simulating gas exchange between plants and the atmosphere.  Meanwhile, modification of m and V_cmax (and J_max) successively based on water stress severity might be adopted to simulate gas exchange between plants and the atmosphere under drought.

Fungal secreted proteins that contain the Common in Fungal Extracellular Membrane (CFEM) domain are important for pathogenicity.  The hemibiotrophic fungus Colletotrichum graminicola causes the serious anthracnose disease of maize.  In this study, we identified 24 CgCFEM proteins in the genome of C. graminicola.  Phylogenic analysis revealed that these 24 proteins (CgCFEM1–24) can be divided into 2 clades based on the presence of the trans-membrane domain.  Sequence alignment analysis indicated that the amino acids of the CFEM domain are highly conserved and contain 8 spaced cysteines, with the exception that CgCFEM1 and CgCFEM24 lack 1 and 2 cysteines, respectively.  Ten CgCFEM proteins with a signal peptide and without the trans-membrane domain were considered as candidate effectors and, thus were selected for structural prediction and functional analyses.  The CFEM domain in the candidate effectors can form a helical-basket structure homologous to the Csa2 protein in Candida albicans, which is responsible for haem acquisition and pathogenicity.  Subcellular localization analysis revealed that these effectors accumulate in the cell membrane, nucleus, and cytosolic bodies.  Additionally, 5 effectors, CgCFEM6, 7, 8, 9 and 15, can suppress the BAX-induced programmed cell death in Nicotiana benthamiana with or without the signal peptide.  These results demonstrate that these 10 CgCFEM candidate effectors with different structures and subcellular localizations in host cells may play important roles during the pathogenic processes on maize plants.

 

Neurotransmitters are important in the maintenance of phase transformation of Locusta migratoria (Arthropoda: Orthoptera).  Here, the effects of the entomopathogen Paranosema locustae on the neurotransmitter taurine in migratory locusts were studied using biochemical methods.  After inoculation with P. locustae, the taurine content of infected locusts significantly declined, but F/C values (ratio between the length of hind femur and the width of the head of locust) increased significantly, compared to healthy locusts.  Meanwhile, F/C values of infected locusts that were injected with 2 µg of taurine showed no significant differences from those of healthy locusts, demonstrating that supplemental taurine inhibited the changes in morphological phase caused by P. locustae.  Paranosema locustae infection also caused longer developmental durations and lower body weights of locusts, but these changes were unaffected after injection with taurine.  These results provided new insights into the mechanisms by which microsporidian parasites affected their locust hosts.

Light spectrum plays an important role in regulating the growth and development of in vitro cultured potato (Solanum tuberosum L.) plantlets.  The status of potato plantlets at the end of in vitro stage influences the minituber production after transplanting.  With 100 μmol m^–2 s^–1 total photosynthetic photon flux density (PPFD), a light spectrum study of 100% red light emitting diodes (LEDs) light spectrum (RR), 100% blue LEDs light spectrum (BB), 65% red+35% blue LEDs light spectrum (RB), and 45% red+35% blue+20% green LEDs light spectrum (RBG) providing illumination at the in vitro cultured stage of potato plantlets for 4 weeks using fluorescent lamp as control (CK) was performed to investigate the effects of LEDs light spectrum on the growth, leaf anatomy, and chloroplast ultrastructure of potato plantlets in vitro as well as the minituber yield after 2 months transplanting in the greenhouse.  Compared to CK, RB and RBG promoted the growth of potato plantlets in vitro with increased stem diameter, plantlet fresh weight, plantlet dry weight, and health index.  Furthermore, BB induced the greatest stem diameter as well as the highest health index in potato plantlets in vitro.  Root activity, soluble protein, and free amino acid were also significantly enhanced by BB, whereas carbohydrates were improved by RR.  In addition, thickness of leaf, palisade parenchyma and spongy parenchyma was significantly increased by BB and RBG.  Chloroplasts under BB and RBG showed well-developed grana thylakoid and stroma thylakoid.  Unexpectedly, distinct upper epidermis with greatest thickness was induced and palisade parenchyma and spongy parenchyma were arranged neatly in RR.  After transplanting in the greenhouse for 2 months, potato plantlets in vitro from BB, RB, and RBG produced high percentage of large size tuber.  BB improved fresh and dry weights of the biggest tuber but decreased tuber number per plantlet.  In addition, RBG increased tuber number as well as tuber fresh and dry weight slightly.  Our results suggested monochromatic blue LEDs as well as combined red, blue or/and green LEDs light spectrum were superior to fluorescent lamp spectrum in micro-propagation of potato plantlets.  Therefore, the application of RBG was suitable; BB and RB could be used as alternatives.

Leguminous crops play a vital role in enhancing crop yield and improving soil fertility.  Therefore, it can be used as an organic N source for improving soil fertility.  The purpose of this study was to (i) quantify the amounts of N derived from rhizodeposition, root and above-ground biomass of peanut residue in comparison with wheat and (ii) estimate the effect of the residual N on the wheat-growing season in the subsequent year.  The plants of peanut and wheat were stem fed with ¹⁵N urea using the cotton-wick method at the Wuqiao Station of China Agricultural University in 2014.  The experiment consisted of four residue-returning strategies in a randomized complete-block design: (i) no return of crop residue (CR0); (ii) return of above-ground biomass of peanut crop (CR1); (iii) return of peanut root biomass (CR2); and (iv) return of all residue of the whole peanut plant (CR3).  The 31.5 and 21% of the labeled ¹⁵N isotope were accumulated in the above-ground tissues (leaves and stems) of peanuts and wheat, respectively.  N rhizodeposition of peanuts and wheat accounted for 14.91 and 3.61% of the BG15N, respectively.  The ¹⁵N from the below-ground ¹⁵N -labeled of peanuts were supplied 11.3, 5.9, 13.5, and 6.1% of in the CR0, CR1, CR2, and CR3 treatments, respectively.  Peanut straw contributes a significant proportion of N to the soil through the decomposition of plant residues and N rhizodeposition.  With the current production level on the NCP, it is estimated that peanut straw can potentially replace 104 500 tons of synthetic N fertilizer per year.  The inclusion of peanut in rotation with cereal can significantly reduce the use of N fertilizer and enhance the system sustainability.