Genetic diversity is the variation occurred in genetic information, which depends on frequency and diversity of alleles among individuals within a population or a species. This phenomenon, which is also a part of the evolution process, allows the organisms to adapt to changing conditions and to survive. Populations with high allelic variability are more easily adaptable to changing environmental conditions. However, nowadays, constant use of populations with certain characters in the plant breeding and the uniformity of consumer demands are among one of the causes of genetic erosion. Loss of genetic diversity within a species can lead to loss of useful properties for human beings. If stress conditions such as disease or drought occur, the ability of a population to survive by adapting to this new condition is dependent on the presence of individuals carrying gene alleles that need to adapt to these conditions.

Abiotic stress conditions caused by increasing anthropogenic activities over the years necessitate using marginal waters in agricultural irrigation and pose a risk to public health by causing salt stress and heavy metal pollution in the soil. The study exposed rocket (Eruca sativa L.), cress (Lepidium sativum L.), and parsley (Petroselinum crispum Mill.) plants to heavy metals (Zn, Cu, Ni, Pb, Cd, and Cr at rates of 300, 140, 75, 300, 3, and 100 mg kg⁻¹, respectively) and salt stress (3, 6, and 9 dS m⁻¹). Both stress conditions affected plant growth negatively. Biomass losses reaching 88% occurred in the rocket, which was determined to be more sensitive to salt stress than heavy metal stress. In parsley, on the other hand, it was determined that the above‐ground organs were more affected by salt stress, but the negative effect of heavy metal stress on the roots was higher than salt stress. In cress, the cultivars produced different responses to stress factors. The Zeybek cultivar was more affected by salt stress, and Bahargülü was more affected by heavy metal stress. In general, an increase in macro‐ and micronutrients was found under stress conditions. In addition, it was determined that the plants were hyper‐accumulative in terms of lead absorption and were sorted as cress > parsley > rocket in terms of metal uptake. According to these findings, these plants should be grown taking into account the lead values in the soil, and consumers should be aware that they are a group of vegetables that accumulate lead.

Common bean (Phaseolus vulgaris L.) is widely grown around the world and sensitive to stress conditions. Accumulation and degradation of amino acids are informative indicators of plant tolerance. In this study, the vegetative growth and amino acid profiles of two common bean cultivars (Öz Ayşe and F16) under salt stress (50, 100, 150, 200 mM NaCl) were investigated to determine the hormetic effect of low-dose gamma rays (10, 20, 30, 40 Gy ⁶⁰Co). The irradiated mature embryos of seeds were regenerated in vitro using embryo cultures. The effects of gamma rays on vegetative growth and amino acid profile under stress and non-stress conditions differed. In terms of vegetative growth, 10 Gy for ‘Öz Ayşe’ and 20 Gy for ‘F16’ had hormetic effects and stimulated plant growth under non-stress conditions. Under salt stress conditions, the effect of gamma rays varied according to the severity of the stress. 30 Gy for ‘Öz Ayşe’ and ‘F16’ at 100 mM salt stress had hormetic effects on vegetative growth. The combined effects of salt stress and gamma rays on the amino acid profile are supported by the vegetative growth results of the plants. Amino acid accumulation occurred at 100 mM at 30 Gy for ‘Öz Ayşe’ and ‘F16’. The most accumulated amino acids were glutamic acid (127.63 mg kg^-1), alanine (173.07 mg kg^-1), glutamine (188.96 mg kg^-1), proline (124.50 mg kg^-1), tyrosine (29.23 mg kg^-1) in ‘Öz Ayşe’ and tyrosine (29.88 mg kg^-1) in ‘F16’ under stress. This study shows that low-dose gamma application under moderate stress conditions has a hormetic effect, not under severe salt stress.

In this study, the effects of exogenous silicon dioxide applications (0.5, 1, 1.5 mM SiO2) on the germination parameters of carrot seeds were investigated under salt stress conditions (150, 200 mM NaCl). For this purpose, germination percentage (GP), mean germination time (MGT), germination rate coefficient (CVG), germination rate index (GRI), germination index (GI), seedling viability index (SVI), leaf number, shoot and root lengths (mm) and plant fresh weight (g) were determined. Germination parameters of yellow carrot, sensitive to salt stress, were adversely affected by 150 mM NaCl application and shoot and root lengths were reduced by 80%. Especially SiO2 applications had a positive effect on germination parameters for the cultivar. In 150 mM NaCl application, the germination of the seeds treated with 0.5 mM SiO2 increased approximately two times (23%), and 15% germination was obtained in 200 mM NaCl, which did not germinate in the control. Although the black carrot cultivar tolerated salt stress, silicon dioxide treatments had a stimulating effect on germination and development. It was determined that especially 1.5 mM SiO2 application in black carrot seeds had a positive effect on germination parameters. Germination percentage increased to 93% in seeds treated with 1.5 mM SiO2 in 150 mM NaCl, and 86% at 200 mM NaCl concentration, reaching higher values compared to the control group. The results showed that pre-treatment with appropriate silicon concentrations significantly improved germination performance and promoted tolerance to the salt stress.

Bu çalışma, farklı turp çeşitlerinin (beyaz, siyah, kırmızı, kırmızı fındık turp) tuz stresi koşullarında tolerans düzeylerini belirlemek ve dışarıdan salisilik asit (SA) uygulamasının çimlenme ve vejetatif gelişim üzerine etkinliğini tespit etmek amacıyla yapılmıştır. Bu amaçla; çimlenme yüzdesi (%), çimlenme süresi, çimlenme indeksi hesaplanmış, ayrıca yaprak sayısı (adet), sürgün boyu (cm), kök uzunluğu (cm), yaprak genişliği (cm), yaprak uzunluğu (cm), gövde çapı (mm), bitki yaş ve kuru ağırlıkları (g) ölçülmüştür. Turp tohumları kontrol, 100 mM, 150 mM ve 200 mM tuz konsantrasyonlarında çimlenmeye tabi tutulmuştur. Tuz stresi çimlenmeyi yüksek oranda inhibe etmemiş ancak bitkilerin vejetatif gelişimlerini olumsuz etkilemiştir. Elde edilen verilerin istatistik analiz sonuçlarına göre 150 mM eşik değer olarak belirlenmiştir. Daha sonra 150 mM tuz konsantrasyonu uygulanan tohumlara farklı dozlarda (0,25, 0,50, 0,75, 1,00 mM) SA ilavesi yapılmış ve çimlenme yüzdeleri açısından tüm çeşitlerde 0,50 mM SA uygulanabileceği sonucuna ulaşılmıştır. Bununla birlikte 1 mM SA uygulaması iri kırmızı ve kırmızı fındık turp çeşitlerinde çimlenmeyi inhibe etmiş, ani ve ciddi çimlenme kayıplarına neden olmuştur (%10, %8, sırasıyla). SA‘in vejetatif gelişim parametreleri üzerine olan etkileri çeşide göre farklılık göstermiş olup, beyaz turp çeşidinde vejetatif gelişim özellikleri açısından inhibe edici olduğu belirlenmiştir. Diğer taraftan siyah ve iri kırmızı turp çeşitlerinde 0,50 mM, kırmızı fındık turp çeşidinde ise 0,75 mM SA uygulaması vejetatif gelişim açısından olumlu sonuç vermiştir.