Programmed cell death (PCD) is relevant to many aspects in the growth and development of a plant organism. In their reproduction, many flowering plant species possess self-incompatibility (SI), that is an intraspecific reproductive barrier, which is a genetic mechanism ensuring the avoidance of inbreeding depression by preventing self-pollination. This phenomenon enhances intraspecific variation; however, SI is rather a hindrance for some fruit plant species (such as plum, cherry, and peer trees) rather than an advantage in farming. PCD is a factor of the S-RNase–based SI in Petunia hybrida E. Vilm. The growth of self-incompatible pollen tubes (PTs) is arrested with an increase in the activity of caspase-like proteases during the first hours after pollination so that all traits of PCD—plasma membrane integrity damage, DNA degradation/disintegration, and damage of PT structural organization (absence of vacuoles, turgor disturbance, and separation of cell plasma membrane from the cell wall)—are observable by the moment of PT growth arrest. We succeeded in discovering an additional cytological PCD marker, namely, the formation of ricinosomes in self-incompatible PTs at early stages of PCD. SI is removable by treating petunia stigmas with Acetyl-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO), an inhibitor of caspase-3/DEVDase, 2 h before a self-incompatible pollination. In this process, the level of caspase-3-like protease activity was low, DNA degradation was absent, PTs grew to the ovary, fertilization was successful, and full-fledged seeds were formed.

The processes of growth and development in plants involve programmed cell death (PCD). For members of the Solanaceae family, such as Petunia hybrid E. Vilm and Solanum pennellii Correll, the phenomenon of S RNase-based self-incompatibility (SI) is characteristic. This mechanism helps maintain population heterozygosity and prevents inbreeding. However, in breeding, SI is often more of a hindrance than an advantage. It has been proven that PCD is a key factor in gametophytic SI in S. pennellii. In the present study, by treating tomato stigmas with Acetyl-Asp-Glu-Val-Asp-aldehyde (Ac DEVD-CHO) (a caspase-3/DEVDase inhibitor) at a concentration of 0.0625 mM two hours before self-incompatible pollination, it was possible to overcome SI. As a result, pollen tubes grew to the ovary, fertilization occurred, and fully developed seeds were formed.

The potential role of reactive oxygen species (ROS) is studied in the male gametophytes of petunia (Petunia hybrida E. Vilm.) grown in vivo with a focus on its germination, growth support in the progamic stage of fertilization, and the function of the mechanism underlying S-RNase-based self-incompatibility. Exogenous treatment with H₂O₂ influences the in vivo germination and polar growth of pollen tubes (PTs), which manifests as the acceleration or inhibition of these processes depending on its concentration, time interval after pollination, and pollination variant. The H₂O₂ treatment of the stigma somewhat stimulates the PT elongation in the late stages of self-incompatible pollination (4–8 h) versus the strong PT inhibition observed during the first hour of germination. A different pattern is observable in cross-compatible pollination: the H₂O₂ treatment of pistils inhibits PT growth during the overall pollination at all tested concentrations. Treatment of pistils with the NADPH oxidase inhibitor diphenylene iodonium chloride (DPI) strongly inhibited the growth of PTs in both pollination variants. In addition, DCF-DA staining confirms that ROS are formed in pollen, PTs, stigma of nonpollinated pistil, and the pistil itself in all pollination variants. The PT growth during the function of the self-incompatibility mechanism is arrested at high ROS concentrations, which is presumably associated with the SI-induced programmed cell death. Our results demonstrate that ROS are a necessary component of pollen, PTs, exudate, and stigma cells and contribute to successful reproduction. This study provides a deeper insight into the ROS functions during the PT growth in an in vivo system.

The in vitro growth of the pollen tube (PT), an object of comprehensive and intensive research, is a model for studying the mechanisms of sexual reproduction in higher plants. We have studied the potential role of reactive oxygen species (ROS) in the in vitro germination and growth maintenance of the petunia (Petunia hybrida E. Vilm.) male gametophyte. The exogenous treatment with H₂O₂ influences the PT germination and polar growth in vitro. The addition of H₂O₂ to culture medium increases both the percentage of pollen grain germination and the PT length in the case of long cultivation, but inhibits both processes during the first hour of cultivation. This suggests that endogenous ROS play a decisive role in the early stages of pollen germination, with the sensitivity to endogenous ROS emerging later over the course of their growth. The addition of diphenylene iodonium chloride (DPI), a NADPH oxidase inhibitor, considerably decreases both the germination and the growth of the petunia male gametophyte at low concentrations (0.1 μM), and completely arrests the growth at high concentrations (1 μM). ROS are necessary for polar growth of the petunia male gametophyte; they are secreted in the early stages of pollen grain activation and are further localized to the initiation of the PT, mainly in the PT apical part, during polar growth, as confirmed with the help of intravital fluorescence microscopy.

Cereals are the basis of human nutrition, accounting for more than 50% of the daily calorie intake in the world. A valuable feed crop is triticale, which is successfully used in bakery production in a number of countries. To date, this cereal is the host of more than 40 species of aphids, including the common grass aphid Schizaphis graminum R., one of the most common and most malicious. The main method of regulating the number of sucking pests is the use of pesticides, various fertilizers, and plant growth regulators (PGRs). In this study, the effect of the PGRs Verva and Ecopin on the reproductive ability of S. graminum when feeding insects on spring triticale was investigated. Common grass aphids were planted on 20 samples of spring triticale. Plants with planted aphids were treated once with the PGR Verva at a concentration of 1 mL/L and Ecopin at a concentration of 1 g/10 L. The pest population was assessed on the second and fourth days after planting. A sharp increase in the number of offspring in aphids was detected on 18 samples of treated PGR two days after planting, and by day 4 it had doubled. Only in two of the studied samples of experimental plants, had treatment with the PGR used had practically no effect on the number of pests. Future research should focus on studying the mechanisms of aphid-induced chlorosis and the role of aphid saliva proteins in inducing a physiological response in plants.

Distant hybridization is an important breeding strategy that can effectively expand the genetic pool for developing new, high-yielding, and stress-resistant cultivars. However, reproductive isolation often hinders the application of this approach. Intergeneric reproductive barriers (IRBs) manifest during pollen–pistil interactions in plants belonging to different genera, yet the mechanisms underlying these barriers remain largely unknown. In this study, we investigated pollen–pistil interactions during the progamic phase of fertilization in three Solanaceae species using several intergeneric cross combinations. Pollen of all tested species germinated on the stigma surface, grew through the stylar transmitting tissue, and ceased elongation at a distance of 300–920 µm therefrom due to the action of a reproductive barrier. We suggest that programmed cell death (PCD) is a factor contributing to IRBs in Solanaceae. The obtained data indicate that, in all cross combinations, the rejection of incompatible pollen tubes (PTs) is accompanied by increased activity of caspase-like proteases (CLPs), as confirmed by in vivo visualization of active CLPs and spectrophotometric measurement of their activity. Specifically, incompatible PT growth in stylar tissues during the first 4 h after pollination was accompanied by a five- to six-fold increase in caspase-3-like protease activity. Notably, the arrest of PT growth in distant hybridization shows striking similarity to that observed during S-RNase-based self-incompatibility (SI) in Solanaceae. We anticipate that further research will ultimately provide insights into the regulation of reproductive barriers during distant hybridization.