Growth is one of the parameters most affected by the different types of stress, under waterlogging conditions, growth reduction has been reported in cotton (Gossypium hirsutum L.) (Kuai et al. 2015; Zhang et al. 2021b), tomato (Solanum lycopersicum L.) (Reid and Crozier 1971; Zhou et al. 2022), wheat (Triticum aestivum) (Huang et al. 2012; Ciancio et al. 2021), lulo (Solanum quitoense Lam) (Flórez-Velasco et al. 2015) and beans (Velasco et al. 2019)In this study, the waterlogging duration caused a reduction in growth like that reported for beans (Velasco et al. 2019; Posso et al. 2020). In cotton plants, different periods of waterlogging reduced growth in terms of plant height even after the end of the waterlogging (Kuai et al. 2015). In our study, the reduction in stem length was greater in the STW but increased in the STW-RP. The smallest decrease in stem length in the LTW could be due to an ethylene-mediated elongation response as observed in other plant species (Bailey-Serres and Voesenek 2008). The formation of adventitious roots has been considered a trait of acclimatization to waterlogging (Xu et al. 2022; Geng et al. 2023)and is reported in plants such as mung bean (Kumar et al. 2013), corn (Geng et al. 2023), wheat (Xu et al. 2022) and barley (Nuruzzaman Manik et al. 2022). Here, an increase in the number of adventitious roots was found in the STW and LTW, however, the adventitious roots do not exceed three mm in length (data not shown), which suggests that in bean plants need could be need more time to elongate adventitious roots or it have not energy to boost adventitious roots growth. They are probably not associated with tolerance in bush beans. The development of adventitious roots not associated with tolerance has been observed in tomato plants (S. lycopersicum L.) and is induced by the low availability of oxygen in the soil (Vidoz et al. 2010).
The effect of waterlogging on photosynthetic parameters in plants has been widely reported (Kumar et al. 2013; Najeeb et al. 2015; Pan et al. 2021). Our results show during the waterlogging and recovery the reduction in Pn and gs, which suggests that the decrease in Pn may be due in part to a stomatal limitation. The waterlogging induces cytoplasmic acidification and protonation of aquaporins, affecting the water intake and the hydraulic conductivity of the root, causing stomatal closure(Tournaire-Roux et al. 2003). On the other hand, the increase in Ci found here suggests the decrease in Pn may also be associated with the presence of non-stomatal limitations (Farquhar and Sharkey 2003; Sun et al. 2013; Olorunwa et al. 2022).
During the STW-RP, only an increase in Pn was observed while gs, E and Ci did not show variations indicating that this period of waterlogging produces a stress that allows the plant to recover its photosynthetic activity although in a low proportion. Ahmed et al. (2002) found increases in Pn in plants of mung beans (Vigna radiata L.) subjected to 8 days of waterlogging and recovery. Likewise, in this study during the STW-RP, WUE increased, indicating that E decreased more than Pn. According to Pezeshki (2001), low gs can maintain the plant water balance by reducing water losses through transpiration. It has been reported that plants that have high rates of Pn and WUE may have higher growth and yield potential under fluctuating environmental conditions (Jones 1993). In this way, our results suggest that ICA-Cerinza bean plants subjected to the STW have a greater potential for growth and yield than those subjected to the LTW. Sheshshayee et al. (1996) reported the Ci/gs ratio as an indicator of mesophyll efficiency. In this study, an increase in Ci/gs values was found in both periods of waterlogging and recovery, which indicates a reduction in mesophyll efficiency. A high relation between the relation Ci/gs and the content and efficiency of the Rubisco has been reported (Sheshshayee et al. 1996). In plants of clover (Trifolium pratense L.), tomato (S. lycopersicum L.) and cowpea (Olorunwa et al. 2022) has been reported a reduction in Rubisco levels due to waterlogging (Ahsan et al. 2007; Stoychev et al. 2013). These reports, together with the increase in Ci observed in this study, support that the reduction in photosynthesis is also due to non-stomatal limitations.
Decline in Fv/Fm have been associated with damage to PSII and have been observed in many plants under stress conditions (Zhao et al. 2014; Lin et al. 2022). Here, it was observed possible damage in PSII due to Fv/Fm decline in the LTW-RP. In addition, ФPSII, ETR and qP were similarly reduced, suggesting an effect of waterlogging on the efficiency of the photosynthetic apparatus in LTW and LTW-RP. Likewise, there was an increase in NPQ that may be associated with photoprotection mechanisms such as the xanthophyll cycle (Adams et al. 1995; Zhang et al. 2021a). These results are different from that reported by Smethurst et al. 2005 who found, in alfalfa plants (Medicago sativa L.), a complete recovery of the fluorescence parameters of chlorophyll in the drainage period, after 20 days of waterlogging. During STW, a reduction in qP was observed and during STW-RP an increase in qP that is consistent with the increase in Pn was observed.
A decrease in the chlorophyll content as a common symptom in plants subjected to waterlogging (Rao and Li 2003; Yu et al. 2019). Here, only a reduction in Chl a and Chl Total content during the STW-RP was observed, while in the LTW and LTW-RP had a reduction in the Chl content. Likewise, during the LTW-RP there was a decrease in Chl b and Car indicating a greater degradation. Similar data have been reported in bean plants (V. faba L.), where waterlogging caused a decrease in the Chl a content and that remained during the recovery period (Pociecha 2013). It is known that waterlogging induces the synthesis of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) that is transported to the aerial part of the plant and converted into ethylene, a hormone that induces the activation of enzymes that degrade chlorophylls (Christianson et al. 2010; Sharma et al. 2022). Likewise, the reduction of chlorophylls can also be a mechanism of photoprotection under stress conditions, since it reduces the number of photons absorbed by the leaves (Galmés et al. 2007). The reduction in the chlorophyll and carotenoid content observed in this study may be associated with the reduction in Fv/Fm (Shangguan et al. 2000; Sharma et al. 2022).
The stability of the cell membrane in plants is directly related to the functioning of cellular metabolism and under stress conditions, it is highly affected by the presence of reactive oxygen species (ROS) (Silva et al. 2020; Mittler et al. 2022). Under waterlogging conditions, an increase in ROS has been found due to the production of O2- dependent on NADPH oxidase (Qi et al. 2019). Likewise, lipid peroxidation changes the permeability of the membrane, so electrolyte leakage is a measure of the integrity of the membrane (Zhang et al. 2019). Here we found an increase in MDA content and electrolyte leakage only in the STW, Bansal and Srivastava (2015) found in pigeon plant (Cajanus cajan L. Mill) subjected to six days of waterlogged increase in damage to the cell membrane. During the LTW the MDA content and electrolyte leakage did not vary with respect to control plants suggesting the presence of a defense response at the level of production of antioxidants or protective molecules of the membranes. Pociecha (2013) reported increases in the activity of enzymes Peroxidases and Ascorbate peroxidase in bean plants (V. faba L.) subjected to waterlogging and 7 days of recovery. The increase in the synthesis of the proline has been reported in response to different abiotic stresses where it is attributed a role as osmolyte and antioxidant (Hamilton and Heckathorn 2001; Claussen 2005; Barickman et al. 2019). The accumulation of proline observed here during LTW, and LTW-RP may explain in part that no damage to the stability of the membrane has occurred in the LTW as suggested by the MDA content and electrolyte leakage data. However, the Fv/Fm was lower in these plants, may be the concentration of proline produced is not sufficient to prevent PSII damage in bush beans plants. Otherwise, plants of Capsicum sp dramatically increase the proline content when subjected to waterlogging conditions, which confers a slight resistance to waterlogging (Ou et al. 2011).