The impact of estrogens and androgens on plant growth was already described in the first half of the 20th century (reviewed by
[12]). In the last 20 years, few new works have been published that describe the effects of these hormones on plant growth, development, or other processes, as well as revealing some of the mechanisms of their action in detail. Interestingly, however, in recent years, there has been a number of works that have been devoted to the study of the impact of these mammalian hormones on plants due to the fact that they are found in waste or sewage and thus are ‘artificially’ introduced into the environment
[22][23][24][25]. In these works, the authors show that high concentrations of estrogens have a harmful effect on plant growth, morphology, and development. According to Adeel et al.
[25], in lettuce, the application of estrogen (17β-estradiol 10 mg/L) significantly reduced the total root growth and development, which was connected to an increased accumulation of H
2O
2, higher lipid peroxidation, and a higher activity of the antioxidant enzymes. Moreover, 17β-estradiol (at the same concentration), when applied to corn, inhibited kernel germination and corn seedling growth
[24]. The studies of Brown
[23] were devoted to determining the effects of mammalian estrogens (17β-estradiol, estrone, and estriol) on the growth and tuberisation of potato plants (
Solanum tuberosum L.). At a concentration of as low as 0.1 mg/L, estrogen reduced root growth, while 10 mg/L of estrogen caused plant deformities and induced a callus. Tuber production was slightly lower in the plants to which estrogen had been applied, compared with the control. Estrogens at a concentration of 10 mg/L also lowered the activity of an enzyme (acid phosphatase) that is important in plant mineral management, etc.
Although these reports proved that at high concentrations, estrogens have an inhibitory effect on the growth processes in plants, simultaneously, at lower concentrations, they might have a biostimulative effect on metabolism. In lettuce, estrogens that were applied at concentrations of 0.1–50 µg/L enhanced the photosynthetic pigments, root growth, and shoot biomass
[25]. In addition, 17β-estradiol (10
−6 M) stimulated the accumulation of the photosynthetic pigments in
Wolffia arrhizal [22]. Dumlupinar et al.
[26] found that a 10
−6 M concentration of 17β-estradiol and androsterone, when applied to seven-day-old barley seedlings via spraying, increased the concentrations of calcium, magnesium, phosphorus, sulphur, copper, manganese, aluminium, zinc, iron, potassium and chlorine most effectively, while they decreased the sodium concentration in barley leaves (measured 18 days after spraying). Further, 17β-estradiol (at a concentration of 0.1 mg/L) stimulated germination and seedling growth in corn
[24]. According to Brown
[23], however, even at 0.1 mg/L, estrogens reduced root growth in potato plants although the acid phosphatase activity of the plants increased. In chickpea (
Cicer arietinum) plants, a concentration of 17β-estradiol and androsterone 10
−9 M (applied to seven-day-old plants) was the most active in stimulating plant growth, which was connected with an increased protein and sugar content 18 days after spraying
[27]. The contents of mineral elements such as K, S, Na, Ca, Mg, Zn, Fe, P, Cu, and Ni were higher, whereas Mn and Cl were lower
[28]. The same concentration of these steroids also effectively lowered the H
2O
2 content and lipid peroxidation along with a higher activity of the antioxidative enzymes
[27]. Erdal and Dumlupinar
[29] studied also the effects of 17β-estradiol on germination, root and shoot growth, and the biochemical background (among the other activity of
α-amylase) in chickpea. The seeds, which had been germinated at a few concentrations of steroid from 10
−4 to 10
−15 M were then analysed at the end of the 1st, 3rd, and 5th days. Based on the results, 17β-estradiol accelerated seed germination at the end of days 1 and 3, and the root, and shoot growth was also stimulated. The most effective concentrations of 17β-estradiol were in the range of 10
−9–10
−12 M. These effects were accompanied by an increase in the activity of
α-amylase during germination. The effect of 17β-estradiol, estrone, and androsterone on the in vitro regeneration of
Triticale mature embryos was described by Uysal and Bezirganoglu
[30]. Estrogens had the best result on the percentage of explants that formed shoots.