Biology subjects

Rachmilevitch, S.

Publications and source records attributed to Rachmilevitch, S..

3 recordsLinked to original sources

bioRxiv2023

Importance of Leaf Age in Grapevines Under Salt Stress

The combined effects of salt stress and leaf age on photosynthesis and stomatal conductance are not fully understood. Salt stress develops at different rates in various plant organs and tissues, leading to osmotic and ionic stresses. We studied the development of salt stress (30 mM NaCl) in two grapevine rootstocks by examining the gas exchange, photochemistry, and salt accumulation of leaves at different ages. Our results indicate that leaf age strongly affected photosynthesis but had a minor effect on stomatal conductance in both control and salinity conditions. Surprisingly, salt stress lowered stomatal conductance but had little effect on photosynthesis, opposite to the leaf age effects. Reduction in photosystem II efficiency explained the age-associated decline in photosynthesis, suggesting that the light-dependent phase of photosynthesis is the first process affected by leaf aging. We also found that the sodium exclusion capacity decreased as leaves matured and was age and variety dependent, indicating the importance of leaf age when sampling for salt tolerance studies. Therefore, we suggest that sampling only young leaves is missing critical information in the evaluation of salt-tolerant traits in grapevines.

plant biology↗

bioRxiv2021

Biomass accumulation and physiological responses of tomato plants to magnetically-treated water in hydroponic conditions

Magnetically-treated water (MTW) has been reported to enhance biomass accumulation in plants. However, the underlying mechanisms are not fully understood, and the existing reports only deal with soil-grown plants. Thus, the purpose of this experiment was to assess whether or not MTW affects main physiological processes (gas exchange, biomass accumulation and water potential) in tomato plants whose water supply was only MTW. Two experiments were done in hydroponic semi-controlled conditions, consisting of a loop system with permanent recirculation of water through a non-uniform magnet. The plants grown under MTW showed a significant increase in chlorophyll content, photosynthesis and transpiration at high light irradiances, although the increase in stomatal conductance was less significant. MTW also increased fruit fresh biomass, number of fruits and root dry biomass in 61.7 %, 85.3 % and 30.3 % respectively, but this was only achieved at natural sunlight conditions. Moreover, treated plants showed higher root hydraulic conductance and leaf water potential, which is thought to be related with a lower surface tension of MTW, an effect that is consistent with previous studies. The higher biomass accumulation in tomato plants under MTW is likely explained because of a faster water transport from the roots to the leaves via xylem, which in turn increases H2O efflux and CO2 assimilation in the leaves, thanks to a higher stomatal conductance.

plant biology↗

bioRxiv2020

The bacterial community structure dynamics in Meloidogyne incognita infected roots and its role in worm-microbiome interactions

BackgroundPlant parasitic nematodes such as Meloidogyne incognita have a complex life cycle, occurring sequentially in various niches of the root and rhizosphere. They are known to form a range of interactions with bacteria and other microorganisms, that can affect their densities and virulence. High throughput sequencing can reveal these interactions in high temporal, and geographic resolutions, although thus far we have only scratched the surface. We have carried out a longitudinal sampling scheme, repeatedly collecting rhizosphere soil, roots, galls and second stage juveniles from 20 plants to provide a high resolution view of bacterial succession in these niches, using 16S rRNA metabarcoding. ResultsWe find that a structured community develops in the root, in which gall communities diverge from root segments lacking a gall, and that this structure is maintained throughout the crop season. We detail the successional process leading toward this structure, which is driven by interactions with the nematode and later by an increase in bacteria often found in hypoxic and anaerobic environments. We show evidence that this structure may play a role in the nematodes chemotaxis towards uninfected root segments. Finally, we describe the J2 epibiotic microenvironment as ecologically deterministic, in part, due to active bacterial attraction of second stage juveniles. ConclusionsHigh density sampling, both temporally and across adjacent microniches, coupled with the power and relative low cost of metabarcoding, has provided us with a high resolution description of our study system. Such an approach can advance our understanding of holobiont ecology. Meloidogyne spp., with their relatively low genetic diversity, large geographic range and the simplified agricultural ecosystems they occupy, can serve as a model organism. Additionally, the perspective this approach provides could promote the efforts toward biological control efficacy.

microbiology↗