Flower senescence is a fundamental aspect of the developmental trajectory in flowers, occurring after the differentiation of tissues, maturation of petals and preceding the growth and development of seeds. It is accompanied by various alterations at the cytological, physiological and molecular levels, similar to other forms of programmed cell death (PCD). It involves an intricate interplay of various plant growth regulators, with ethylene being the key orchestrator in ethylene-dependent petal senescence. Petal senescence mediated by ethylene is marked by various changes like petal wilting, amplified oxidative stress, degradation of proteins and nucleic acids and autophagy. Ethylene crosstalks with other growth regulators and triggers genetic and/or epigenetic reprogramming of genes during senescence in flowers. While our understanding of the mechanism and regulation of petal senescence in ethylene-sensitive species has advanced, significant knowledge gaps still exist, which demand critical reappraisal of the available literature on the topic. A deeper understanding of the various mechanisms and regulatory pathways involved in ethylene-dependent senescence has the capacity to facilitate a more precise regulation of the timing and site of senescence, thus leading to optimized crop yields, enhanced product quality and extended longevity.
Nitric oxide releasing compound sodium nitroprusside (SNP) is regarded as novel chemical to beat the daunting challenges of postharvest losses in cut flowers. In the recent years, it has yielded propitious results as postharvest vase preservative for cut flowers. Our study explicates the efficacy of SNP in mitigating postharvest senescence in Consolida ajacis (L.) Schur cut spikes. The freshly excised C. ajacis spikes were subjected to different SNP treatments viz, 20 μM, 40 μM, 60 μM and 80 μM. The control spikes were held in distilled water. The spikes held in test solutions showed a marked improvement in vase life and flower quality. Our results indicate a profound surge in sugars, phenols and soluble proteins in SNP-treated spikes over control. Moreover, the SNP treatments improved membrane stability as signposted by decreased lipoxygenase activity (LOX). The SNP treatments also upregulated different antioxidant enzymes viz, ascorbate peroxidase (APX), catalase (CAT) and superoxide dismutase (SOD). The current study recommends 40 μM SNP as optimum concentration for preserving floral quality and extending display period of C. ajacis spikes. Together, these findings reveal that SNP at proper dosage can efficiently alleviate deteriorative postharvest changes by modulating physiological and biochemical mechanisms underlying senescence.
Plant leaves provide a unique insight into the changes that occur in organs, tissues and cells as they approach senescence. As part of the parental outlay, plants instigate leaf senescence to reallocate resources from older tissues to new organs towards the termination of the growing season. The aim of crop breeding initiatives is to optimize senescence for specific species. Considering hormonal regulation and their crosstalk during leaf senescence through integration of developmental signals, this work examines the efficacy of polyamines (PAs) in modulating several biochemical and physiological aspects with an ultimate aim to delay leaf senescence in leaf discs of Berginia ciliata (Haw.) sternb. Leaf discs were treated with putrescine (Put), spermidine (Spd) and spermine (Spm) at 20 μM, 20 μM and 15 μM concentration, respectively. A set of leaf discs kept in distilled water served as the control. Leaf discs treated with PAs were green and fresh by about 4 days compared to the control, thus exhibited delayed senescence. This delayed leaf senescence corroborated with the maintenance of high activity of reactive oxygen species (ROS) scavenging antioxidant enzymes viz, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and higher content of chlorophylls. A marked increase was also observed in membrane stability and soluble proteins in leaf discs treated with PAs. Exogenous PAs reduced oxidative stress in the leaf discs, as revealed by lower malondialdehyde (MDA) level, which is manifested as reduced lipid peroxidation (LPO). Improved membrane stability was proportional to lower LPO, as measured by the membrane stability index (MSI).
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