(1) Background: Strawberry plants are strongly affected by heavy-metal-contaminated soils, which affects plant growth, yield and fruit quality. The aim of this work was to study the effects of a combination and individual application of silicon (Si) and humic acid (HA) on growth and development of Rubygem strawberries exposed to cadmium (Cd) in greenhouse conditions. (2) Methods: Morphological, physiological and biochemical parameters, including minerals in roots and leaves were determined. (3) Results: Cd stress in strawberry plants decreased plant fresh and dry weight; leaf stomatal conductance; leaf relative water content and chlorophyll content; number of leaves; leaf area; leaf N, P and K levels; and root P, N, Mg, K and Ca contents. Cd increased membrane permeability, leaf temperature, proline levels and lipid peroxidation. Si and HA individual applications to strawberries mitigated the negative effect of Cd stress on biochemical, physiological, morphological and minerals parameters by decreasing membrane permeability, leaf temperature, proline levels and lipid peroxidation. (4) Conclusions: Our findings highlighted that applications of Si, HA and Si + HA were effective in conferring Cd tolerance in strawberry plants by upregulating their many morphological, physiological and biochemical properties and reducing Cd stress.

Strawberry is a salt-sensitive plant adversely affected by slightly or moderately saline conditions. The growth, fruit, and biochemical parameters of strawberry plants grown under NaCl (0, 30, 60, and 90 mmol L−1) conditions with or without a halophytic companion plant (Portulaca oleracea L.) were elucidated in a pot experiment. Salt stress negatively affected the growth, physiological (stomatal conductance and electrolyte leakage), and biochemical parameters such as chlorophyll contents (chl-a and chl-b); proline, hydrogen peroxide, malondialdehyde, catalase, and peroxidase enzyme activities; total soluble solids; and lycopene and vitamin C contents, as well as the mineral uptake, of strawberry plants. The companionship of P. oleracea increased fresh weight, dry weight, and fruit average weight, as well as the total fruit yield of strawberry plants along with improvements of physiological and biochemical parameters. This study showed that the cultivation of P. oleracea with strawberry plants under salt stress conditions effectively increased strawberry fruit yield and quality. Therefore, we suggest that approaches towards the use of P. oleracea could be an environmentally friendly method that should be commonly practiced where salinity is of great concern.

Carpobrotus acinaciformis L. plant is a kind of halophyte that is able to survive in high salt conditions. It is important to determine its physiological, biochemical and molecular limit of NaCl stress if one aims to use it for phytoremediation purpose. In this study, the alkaline protocol of the modified plant comet assay were used for rapid detection of DNA damage in C. acinaciformis L. plants exposed to a series of NaCl stress concentrations (0-, 50-, 100-, 200-, 300-, 400 and 500 mmol L-1) in hydroponic conditions for 2 weeks. DNA damage was measured as the values of percentage of DNA in tails and tail length. The halophyte C. acinaciformis L. did not show any dose response up to 400 mmol L-1 NaCl level in terms of DNA damages. DNA integrity measured via comet assay showed that DNA preserved its original shape up to 400 mmol L-1 NaCl level. However, the very high concentrations of NaCl (400 and 500 mmol L-1) caused DNA damages. When physiological and biochemical parameters such as proline, chlorophyll a and b, peroxidase (POX), catalase (CAT), H2O2, malondialdehyde (MDA) contents were examined, oxidant molecules such as H2O2 (0.912-3.72 µmol g-1 Fwt) and MDA (7.1-34 nmol g-1 Fwt) gradually increased along with the increase of NaCl concentrations, p<0.05. On the other hand, antioxidant enzyme POX and an osmolyte molecule proline slightly increased up to 400 mmol L-1 NaCl level then slightly decreased after that. Similar issues were obtained from that of protease enzyme which indicates the power of protein hydrolysis in which a slight decrease (182-95 Unit mg-1 protein) over a dose of NaCl was evident. Chlorophyll contents and CAT activity were not affected upon increase of NaCl concentrations. This study showed that the halophyte C. acinaciformis L. can be easily used to remove salt up to 400 mmol L-1 NaCl concentrations from a saline-affected soil. Measuring DNA damage is concluded as a very useful parameter to find out what level of NaCl could be tolerated if a halophyte plant is aimed to remediate the saline soils.