Determinants Of Plant Performance Research Articles

Morphological, physiological, and molecular scion traits are determinant for salt-stress tolerance of grafted citrus plants.

Citrus productivity has been decreasing in the last decade in the Mediterranean basin as a consequence of climate change and the high levels of salinity found in the aquifers. Citrus varieties are cultivated grafted onto a rootstock, which has been reported as responsible for plant tolerance to adverse situations. However, other important factors for stress tolerance relying in the scion have been less studied. The aim of this study was to evaluate the effect of the grafted scion on citrus tolerance to salt stress. Four different citrus rootstock/scion combinations were subjected to salt stress for 30 days, using Carrizo citrange (CC) or Citrus macrophylla (CM) as rootstocks, and Navelina orange (NA) or Oronules mandarin (OR) as scions. CM-OR was the most tolerant combination, whereas CC-NA was the most sensitive one. Our results support the idea that the rootstock plays an important role in salt stress tolerance, but scion is also crucial. Thus, photosynthesis and transpiration, processes regulated by abscisic acid and jasmonic acid, are determinant of plant performance. These photosynthetic parameters were not affected in plants of the salt-tolerant combination CM-OR, probably due to the lower intoxication with Cl- ions, allowing a better performance of the photosynthetic machinery under stress conditions. The different stomatal density of the two citrus scions used in this work (higher in the sensitive NA in comparison to the tolerant OR) also contributes to the different tolerance of the grafted plants to this adverse condition. Additionally, CsDTX35.1 and CsDTX35.2, genes codifying for Cl- tonoplast transporters, were exclusively overexpressed in plants of the salt-tolerant combination CM-OR, suggesting that these transporters involved in Cl- compartmentalization could be crucial for salt stress tolerance. It is concluded that to improve citrus tolerance to high salinity, it is important that scions have a versatile photosynthetic system, an adequate stomatal density, and a proper modulation of genes coding for Cl- transporters in the tonoplast.

Protists as main indicators and determinants of plant performance

BackgroundMicrobiomes play vital roles in plant health and performance, and the development of plant beneficial microbiomes can be steered by organic fertilizer inputs. Especially well-studied are fertilizer-induced changes on bacteria and fungi and how changes in these groups alter plant performance. However, impacts on protist communities, including their trophic interactions within the microbiome and consequences on plant performance remain largely unknown. Here, we tracked the entire microbiome, including bacteria, fungi, and protists, over six growing seasons of cucumber under different fertilization regimes (conventional, organic, and Trichoderma bio-organic fertilization) and linked microbial data to plant yield to identify plant growth-promoting microbes.ResultsYields were higher in the (bio-)organic fertilization treatments. Soil abiotic conditions were altered by the fertilization regime, with the prominent effects coming from the (bio-)organic fertilization treatments. Those treatments also led to the pronounced shifts in protistan communities, especially microbivorous cercozoan protists. We found positive correlations of these protists with plant yield and the density of potentially plant-beneficial microorganisms. We further explored the mechanistic ramifications of these relationships via greenhouse experiments, showing that cercozoan protists can positively impact plant growth, potentially via interactions with plant-beneficial microorganisms including Trichoderma, the biological agent delivered by the bio-fertilizer.ConclusionsWe show that protists may play central roles in stimulating plant performance through microbiome interactions. Future agricultural practices might aim to specifically enhance plant beneficial protists or apply those protists as novel, sustainable biofertilizers.9YGnSNgqaHj2gH_1N6en5wVideo abstract

Elevational trends in leaf size of Campylotropis polyantha in the arid Minjiang River valley, SW China

Leaf traits are determinants of plant performance in ecosystems. The arid Minjiang River valley offer optimal opportunity to reveal climate-leaf function relationship because steep climatic gradients (e.g., dryness and high temperature decreased with elevation). We investigated the leaf size and structure of Campylotropis polyantha occurring in five 80–100 m elevational bands from 1650 m to 2200 m in this arid valley. Plants growing at higher elevations had larger leaves, epidermal cell and leaf thickness with thicker spongy mesophyll and epidermis, but had lower epidermal cell density and cutin thickness. These variations in leaf size and spongy mesophyll as well as cutin and total leaf thickness were mainly associated with annual precipitation and soil water content, while epidermal cell dimensions were associated with temperature. We conclude that water-related factors are the main mechanisms underlying leaf variations across elevations. High air temperature during the growing season imposes multiple stresses on plants at low elevations. The larger leaf size of high elevation plants is related more to their larger spongy mesophyll and epidermal cell sizes than to their larger palisade cell. These results provide a new understanding of functional ecology and the anatomical plasticity of plants in varying environments with different elevations.