“Whispers of withering”: Decoding biochemical and molecular switches orchestrating flower senescence in Consolida ajacis (L.) Schur

Petal senescence is an intrinsic facet of the floral development, encompassing induction of ethylene production, upregulation of PCD-related genes and recycling of nutrients. Morphological, biochemical and molecular dynamics were investigated in different stages spanning from tight bud phase (I) to senescent phase (V) during flower development of Consolida ajacis. Scanning electron microscopic (SEM) analysis revealed distinct alterations in morphology of petal tissues, transitioning from tightly packed striated surfaces at the bud stage to flattened surfaces at senescent stage. Throughout the flower development, senescence-associated genes were notably upregulated, particularly during the senescent stage, which modulated critical physiological processes initiating senescence. Soluble protein concentration exhibited a gradual decline from bud phase through open stage, followed by a pronounced reduction in the senescent stage, mirroring SAG12 (senescence associated gene 12) and DAD1 (defender against death 1) gene expression patterns. Lipid peroxidation increased gradually from bud to bloom stage due to low lipoxygenase (LOX) activity and LOX1 transcript levels, intensified in the senescent stage due to elevated LOX1 (lipoxygenase 1) expression, leading to membrane degradation. Flower development in Consolida ajacis was intricately linked to hormonal turnover with ethylene and ABA content increasing towards senescence due to heightened mRNA transcripts of ACO (1-amino cyclopropane 1 carboxylic acid oxidase) and AAO3 (abscisic aldehyde oxidase 3) genes, while IPT3 (isopentyl tranferase 3) transcript abundance decreased in the senescent stage compared to early developmental stages. Antioxidant system comprising of ascorbate peroxidase (APX), catalase (CAT) and superoxide dismutase (SOD) signposted upsurge from bud to bloom stage and resulted in low hydrogen peroxide (H₂O₂) content. Subsequently during the senescent stage, there was a significant decrease in antioxidant activity due to accumulation of reactive oxygen species (ROS) thereby resulting in oxidative stress.