Abstract
BackgroundThis study describes a promising method for understanding how halophytes adapt to extreme saline conditions and to identify populations with greater resistance. Image and colour analyses have the ability to obtain many image parameters and to discriminate between different aspects in plants, which makes them a suitable tool in combination with genetic analysis to study the plants salt tolerance. To the best of our knowledge, there are no publications about the monitoring of halophytic plants by non-destructive methods for identifying the differences between plants that belong to different maternal salinity environments. The aim is to evaluate the ability of image analysis as a non-destructive method and principal component analysis (PCA) to identify the multiple responses of two S. europaea populations, and to determine which population is most affected by different salinity treatments as a preliminary model of selection.ResultsImage analysis was beneficial for detecting the phenotypic variability of two S. europaea populations by morphometric and colour parameters, fractal dimension (FD), projected area (A), shoot height (H), number of branches (B), shoot diameter (S) and colour change (ΔE). S was found to strongly positively correlate with both proline content and ΔE, and negatively with chlorophyll content. These results suggest that proline and ΔE are strongly linked to plant succulence, while chlorophyll decreases with increased succulence. The negative correlation between FD and hydrogen peroxide (HP) suggests that when the plant is under salt stress, HP content increases in plants causing a reduction in plant complexity and foliage growth. The PCA results indicate that the greater the stress, the more marked the differences. At 400 mM a shorter distance between the factorial scores was observed. Genetic variability analysis provided evidence of the differences between these populations.ConclusionsOur non-destructive method is beneficial for evaluating the halophyte development under salt stress. FD, S and ΔE were relevant indicators of plant architecture. PCA provided evidence that anthropogenic saline plants were more tolerant to saline stress. Furthermore, random amplified polymorphic DNA analysis provided a quick method for determining genetic variation patterns between the two populations and provided evidence of genetic differences between them.
Highlights
This study describes a promising method for understanding how halophytes adapt to extreme saline conditions and to identify populations with greater resistance
Fractal dimension as a measure of plant biomass under different salinity levels This study shows the morphometric characteristics of S. europaea plants from two different populations that demonstrated a positive effect under moderate salinities 200 and 400 mM NaCl for Ciechocinek and 200, 400 and 800 mM NaCl for Inowrocław, while at the extremes
No significant differences between the two populations were found in total chlorophyll content, but in the case of carotenoid content, significant differences were observed (Fig. 5c and d)
Summary
This study describes a promising method for understanding how halophytes adapt to extreme saline conditions and to identify populations with greater resistance. The biological effects of salt stress are very different and may include morphological changes such as variation in height, projected area, shoot thickening, plant branching and foliage complexity They may include plant colour modification due to a reduced photosynthesis that affects nutrient loss, biomass and hydric balance [40]. It was stated that the image analysis combined with genetic analysis is a useful method for explaining the main processes that influence salinity tolerance in plants In this context, − recent studies have been looking for simple, accurate and non-destructive methods to evaluate how abiotic stressors affect plants’ growth [7, 19, 30, 32]. To the best of our knowledge, no studies have been published using colour analysis as an indicator to evaluate salt stress in plants
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