Effects of rainfall patterns on annual plants in Horqin Sandy Land, Inner Mongolia of China

Growth of annual plants in arid environments depends largely on rainfall pulses. An increased understanding of the effects of different rainfall patterns on plant growth is critical to predicting the potential responses of plants to the changes in rainfall regimes, such as rainfall intensity and duration, and length of dry intervals. In this study, we investigated the effects of different rainfall patterns（e.g. small rainfall event with high frequency and large rainfall event with low frequency） on biomass, growth characteristics and vertical distribution of root biomass of annual plants in Horqin Sandy Land, Inner Mongolia of China during the growing season（from May to August） of 2014. Our results showed that the rainfall patterns, independent of total rainfall amount, exerted strong effects on biomass, characteristics of plant growth and vertical distribution of root biomass. Under a constant amount of total rainfall, the aboveground biomass（AGB）, belowground biomass（BGB）, plant cover, plant height, and plant individual and species number increased with an increase in rainfall intensity. Changes in rainfall patterns also altered the percentage contribution of species biomass to the total AGB, and the percentage of BGB at different soil layers to the total BGB. Consequently, our results indicated that increased rainfall intensity in future may increase biomass significantly, and also affect the growth characteristics of annual plants.

Comparison of Effect of Brassinosteroid and Gibberellin Biosynthesis Inhibitors on Growth of Rice Seedlings

Brassinosteroid（BR） and gibberellin（GA） are two predominant plant hormones that regulate plant cell elongation. Mutants disrupt the biosynthesis of these hormones and display different degrees of dwarf phenotypes in rice. Although the role of each plant hormone in promoting the longitudinal growth of plants has been extensively studied using genetic methods, their relationship is still poorly understood. In this study, we used two specific inhibitors targeting BR and GA biosynthesis to investigate the roles of BR and GA in growth of rice seedlings. Yucaizol, a specific inhibitor of BR biosynthesis, and Trinexapac-ethyl, a commercially available inhibitor of GA biosynthesis, were used. The effect of Yucaizol on rice seedlings indicated that Yucaizol significantly retarded stem elongation. The IC_（50） value was found to be approximately 0.8 μmol/L. Yucaizol also induced small leaf angle phenocopy in rice seedlings, similarly to BR-deficient rice, while Trinexapac-ethyl did not. When Yucaizol combined with Trinexapac-ethyl was applied to the rice plants, the mixture of these two inhibitors retarded stem elongation of rice at lower doses. Our results suggest that the use of a BR biosynthesis inhibitor combined with a GA biosynthesis inhibitor may be useful in the development of new technologies for controlling rice plant height.

Effects of soil nitrate:ammonium ratio on plant carbon:nitrogen ratio and growth rate of Artemisia sphaerocephala seedlings

Can soil nitrate： ammonium ratios influence plant carbon： nitrogen ratios of the early succession plant？ Can plant carbon： nitrogen ratios limit the plant growth in early succession？ To address these two questions, we performed a two-factor （soil nitrate： ammonium ratio and plant density） randomized block design and a uniform-precision rotatable central composite design pot experiments to examine the relationships between soil nitrate： ammonium ratios, the carbon： nitrogen ratios and growth rate of Artemisia sphaerocephala seedlings. Under adequate nutrient status, both soil nitrate： ammonium ratios and plant density influenced the carbon： nitrogen ratios and growth rate of A. sphaerocephala seedlings. Under the lower soil nitrate： ammonium ratios, with the increase of soil nitrate： ammonium ratios, the growth rates of plant height and shoot biomass of A. sphaerocephala seedlings decreased significantly; with the increase of plant carbon： nitrogen ratios, the growth rates of shoot biomass of A. sphaerocephala seedlings decreased significantly. Soil nitrate： ammonium ratios affected the carbon： nitrogen ratios of A. sphaerocephala seedlings by plant nitrogen but not by plant carbon. Thus, soil nitrate： ammonium ratios influenced the carbon： nitrogen ratios of A. sphaerocephala seedlings, and hence influenced its growth rates. Our results suggest that under adequate nutrient environment, soil nitrate： ammonium ratios can be a limiting factor for the growth of the early succession plant.

Advances on the Molecular Mechanism of the Interaction between Ralstonia solanacearum and Hosts

Ralstonia solanacearum is an important model phytopathogenic bacterium that causes bacterial wilt disease on many plant species and leads to serious economic losses. The interactions between R. solanacearum and host plants have become a model system for the study of plants and pathogens interactions. This paper reviews the advances on the molecular mechanisms between R. solanacearum and hosts interaction including the formation of plant innate immunity, the suppression of plant innate immunity by this pathogen and the activation of effector-triggered immunity. Furthermore, we made a prospect on how to utilize the interaction mechanism between R. solanacearum and hosts to control the disease.

Effect of Plant Spacing on Growth and Grain Yield of Soybean

In the Philippines, rice monoculture systems are common. Compared to these systems, the rice-soybean cropping system may prove more water-efficient and there is a trend of increasing soybean area in the response to water scarcity and need for crop diversification in the Philippines. A field study was conducted to evaluate the effect of row and plant to plant spacing (20 × 10, 20 × 5, 40 × 10, and 40 × 5 cm) on growth and yield of soybean. Plant height was not influenced by the plant geometry. Spacing, however, influenced leaf area and shoot biomass of soybean. Plants grown at the widest spacing (i.e., 40 × 10 cm) produced lowest leaf area and shoot biomass at 6 and 12 weeks after planting. Leaf area and shoot biomass at other three spacing were similar. There was a negative and linear relationship between weed biomass and crop shoot biomass at 6 and 12 weeks after planting. Grain yield of soybean was not affected by plant geometry and it ranged from 1.3 to 1.9 t·ha-1 at different spacing.

Effect of Plant Geometry on Growth and Yield of Corn in the Rice-Corn Cropping System

The rice-corn cropping system is increasing in Asia in response to increased demand of corn for feed. A field study was conducted to evaluate the effect of plant geometry (row and plant to plant spacing: 50 × 20, 50 × 30, 75 × 20, and 75 × 30 cm) on growth and yield of corn. Plant height and leaf production per plant were not influenced by the plant geometry. Spacing, however, influenced leaf area, aboveground shoot biomass, and yield of corn per unit area. Highest leaf area, shoot biomass, and yield (8.2 t·ha-1) were produced by plants grown at 50 × 20 cm spacing. The results of this study suggest that narrow rows and plant to plant spacing may increase grain yield by increasing crop growth rates. Plant geometry could be modified to improve yield of corn in the rice-corn cropping system, and thereby increase productivity of the system.

Medicinal plants from the Brazilian Amazonian region and their antileishmanial activity:a review

Leishmaniasis, a neglected disease caused by Leishmania protozoans, primarily affects people in tropical and subtropical areas. Chemotherapy based on the use of pentavalent antimonials, amphotericin B, paromomycin, miltefosine and liposomal amphotericin B is currently the only effective treatment. However, adverse effects, long-term treatment and the emergence of parasite resistance have led to the search for alternative treatments. Natural products used in traditional medicine provide an unlimited source of molecules for the identification of new drugs, and the Amazon region has abundant biodiversity that includes several species of plants and animals, providing a rich source of new products and com- pounds. Although the literature describes numerous promising compounds and extracts for combating Leishmania protozoans, the results of such research have not been embraced by the pharmaceutical industry for the development of new drugs. Therefore, this review focused on the antileishmanial activity of extracts, isolated compounds and essential oils commonly used by the local population in the Brazilian Amazonian region to treat several illnesses and described in the literature as promising compounds for combating leishmaniasis.

How can ecosystem engineer plants boost productivity in east Mediterranean drylands

Background Water availability is the key limiting factor for plant productivity in drylands covering ca.40%of Earth’s land surface.For such ecosystems to retain productivity and biodiversity under climatic change,it would be valu-able to identify/promote keystone plant species that(i)have developed strategies to more efficiently utilize moisture resources not easily accessible and(ii)improve moisture conditions for neighboring plants.The very deep-rooted Ziziphus lotus,considered an ecosystem engineer,is one such example.However,it is not known which biotic traits:(a)canopy interception of moisture/rainfall,(b)hydraulic redistribution of deep ground moisture by roots,or non-biotic factors:(c)soil’s volume,and(d)organic matter content,Z.lotus activates/modulates to play such a role.We,thus,selected dryland ecosystems where the plant dominates and measured for potential effects on the less deep-rooted Thymbra capitata.For assessing impacts on ecosystem productivity,we measured the spatial aggregation of ca.3600 T.capitata plants.As a proxy for soil moisture availability and its spatial variability,we conducted a 7-year-long study using thymes’nighttime rehydration.Sampling extended up to 15 m away from Z.lotus.Results The density of T.capitata plants growing up to 5 m around Z.lotus vs.thymes growing 10-15 m away was found significantly increased(2.5-4.5 times),while their stem/leaf moisture was ca.10%higher at predawn compared to nightfall during the dry season.This suggests that ecosystem productivity is driven by a greater soil moisture avail-ability around Z.lotus permitting more thyme daytime transpiration,in contrast to thymes growing further away.The phenomenon appeared only under dry topsoil(during the dry season;becoming stronger during dry years).Morning dew/rainfall interception from the canopy or soil depth/organic matter did not show significant effects,leaving only the hydraulic lift properties of Z.lotus as the most likely driver for soil moisture availability.Conclusions The deep-rooting properties and hydraulic lift potential of Z.lotus may be the key in permitting it to boost ecosystem productivity.Such hydraulic plant traits require more attention as they may prove valuable in com-bating desertification and restoring ecosystems in arid/semiarid regions threatened by climate change.

Piriformospora indica confers cadmium tolerance in Nicotiana tabacum

Piriformospora indica, a root-colonizing endophytic fungus of Sebacinales, promotes plant growth and confers resistance against biotic and abiotic stresses. In order to confirm the influence of P. indica on growth, proline, malondialdehyde（MDA）, chlorophyll, and cadmium（Cd） amounts in Nicotiana tabacum under Cd stress, hydroponics, pot and field trials were conducted. The results showed that P. indica can store Cd in plant roots and reduce leaf Cd content, reduce the concentration of MDA, and increase the proline and chlorophyll content and the activities of catalase, peroxidase, and superoxide dismutase under hydroponic Cd stress. RT-PCR analysis showed that the relative expression level of genes Gsh2, Ta PCS1, oas1, GPX, and Hsp70 in colonized plants was 4.3, 1.4, 2.9, 1.7, and 6.9fold higher than in un-colonized plants respectively. Cd exposure significantly reduced un-colonized plants＇ agronomic traits compared to P. indica-colonized ones. Our results suggested that P. indica can sequester Cd in roots, so that much less cadmium was transported to leaves, and the increased concentrations of antioxidant enzymes, pigments and proline contents, as well as the higher expression of stress-related phytochelatin biosynthesis genes in P. indica-inoculated plants, may also serve to protect N. tabacum plants against oxidative damage, enhancing Cd tolerance.

Perspectives of Using L-Tryptophan for Improving Productivity of Agricultural Crops: A Review

Plant growth regulators are biologically active signaling molecules that regulate a number of plant physiological processes. Auxin(indole-3-acetic acid) is an important plant growth regulator and is synthesized within plant tissues through L-tryptophan(L-TRP)-dependent and-independent pathways. It has been found that plants respond to exogenously applied L-TRP due to insufficient endogenous auxin biosynthesis. The exogenous application of L-TRP is highly significant for normal plant growth and development.L-tryptophan is applied through foliar spray, seed priming, and soil application. Soil-applied L-TRP is either directly taken up by plants or metabolized to auxin by soil microbiota and then absorbed by plant roots. Similarly, foliar spray and seed priming with L-TRP stimulates auxin synthesis within plants and improves the growth and productivity of agricultural crops. Furthermore, L-TRP contains approximately 14% nitrogen(N) in its composition, which is released upon its metabolism within a plant or in the rhizosphere and plays a role in enhancing crop productivity. This review deals with assessing crop responses under the exogenous application of L-TRP in normal and stressed environments, mode of action of L-TRP, advantages of using L-TRP over other auxin precursors, and role of the simultaneous use of L-TRP and auxin-producing microbes in improving the productivity of agricultural crops. To the best of our knowledge, this is the first review reporting the importance of the use of L-TRP in agriculture.