Cross-talk between environmental stresses and plant metabolism during reproductive organ abscission

Abstract

In plants, flowering is a crucial process for reproductive success and continuity of the species through time. Fruit production requires the perfect development of reproductive structures. Abscission, a natural process, can occur to facilitate shedding of no longer needed, infected, or damaged organs. If stress occurs during flower development, abscission can intervene at flower level, leading to reduced yield. Flower abscission is a highly regulated developmental process simultaneously influenced and activated in response to exogenous (changing environmental conditions, interactions with microorganisms) and endogenous (physiological modifications) stimuli. During climate change, plant communities will be more susceptible to environmental stresses, leading to increased flower and fruit abscission, and consequently a decrease in fruit yield. Understanding the impacts of stress on the reproductive phase is therefore critical for managing future agricultural productivity. Here, current knowledge on flower/fruit abscission is summarized by focusing specifically on effects of environmental stresses leading to this process in woody plants. Many of these stresses impair hormonal balance and/or carbohydrate metabolism, but the exact mechanisms are far from completely known. Hormones are the abscission effectors and the auxin/ethylene balance is of particular importance. The carbohydrate pathway is the result of complex regulatory processes involving the balance between photosynthesis and mobilization of reserves. Hormones and carbohydrates together participate in complex signal transduction systems, especially in response to stress. The available data are discussed in relation to reproductive organ development and the process of abscission.

Ethylene-dependent effects on generative organ abscission of Lupinus luteus

“…The changing level of phytohormones is a factor responsible for coordinating the anatomical and physiological changes accompanying organ abscission [9]. Due to the pivotal role of ethylene in the senescence and abscission of different plant organs, we studied the effect of this hormone and of its precursor (ACC) on flower abortion in L. luteus.…”

“…Almost every plant tissue is able to produce ET, but in most cases its level is relatively low, only increasing DOI: 10.5586/asbp.3540 in certain periods of the plant development, such as seeds germination, stem and root growth, abscission of flowers and leaves, fruit ripening, as well as senescence [7]. Other phytohormones affect ethylene production as well (auxins, jasmonates, abscisic acid), similarly to biotic and abiotic external factors that, in ways differentiated in terms of time and space, regulate the transcriptional activity of genes encoding enzymes involved in their biosynthesis [8][9][10][11]. For this process, of key importance are the synthases (ACSs) and oxidases (ACOs) of 1-aminocyclopropane-1-carboxylic acid (ACC) that catalyze the transformation of S-adenosyl-methionine (SAM) into ACC and oxidize ACC to ET, respectively [12,13].…”

Roles of Ethylene Production and Ethylene Receptor Expression in Regulating Apple Fruitlet Abscission

“…The role of ethylene in different abscission processes has long been investigated in diverse plant model and crop species, although most of these studies were focused on the involvement of this hormone at the level of the AZ, where only the last steps of organ shedding take place (Patterson and Bleecker, 2004;Butenko et al, 2006;Meir et al, 2010;Bar-Dror et al, 2011;Sawicki et al, 2015). Taken together, the available information indicates two anatomical layers of ethylene functional involvement: (1) within the AZ, and (2) within the abscising organ.…”

Regulatory roles of sugars in plant growth and development

“…The senescence of leaves is affected by different environmental factors, including nutrients, light, and abiotic and biotic stresses, which often influence photosynthesis, sugar accumulation, and signaling [62]. Hormones and sugars also participate in a complex signal transduction system operating in the process of reproductive organ abscission in response to environmental stress [64].…”