No abstract

No abstract

Deep dormancy of apple (Malus domestica Borkh.) seeds is terminated by a 3-month-long cold stratification. It is expressed by rapid germination of seeds and undisturbed growth of seedlings. However, stimulation of germination of isolated apple embryos is also observed after applying inhibitors of cytochrome c oxidase: nitric oxide (NO) or hydrogen cyanide (HCN) during the first 3-6 h of imbibition of dormant embryos. The aim of this work was to compare the effect of yet another toxic gaseous molecule carbon monoxide (CO) with the effects of HCN and NO on germination of apple embryos and growth and development of young seedlings. We demonstrated that stimulation of germination after short-term pre-treatment with HCN, NO or CO was accompanied by enhanced NO emission from the embryo axes during their elongation. Moreover, similarly high NO production from non-dormant embryos, after cold stratification, was detected. Therefore, we propose that NO may act as signaling molecule in apple embryo dormancy break.

Main conclusionNO accelerates transition of germinated embryos from heterotrophy to autotrophy by stimulation of chloroplasts maturation. NO-mediated autotrophy of apple seedlings correlates to increased content of RuBisCO small subunit and improvement of parameters of chlorophyllafluorescence.Nitric oxide (NO) acts as signaling molecule involved in regulation of various physiological processes in plants, although its involvement in cotyledons greening is poorly recognized. To identify the importance of NO signal for plant growth and development we investigated the effects of short-term application of NO at various developmental stages of seedlings of apple (Malus domestica Borkh.) on cotyledons’ chlorophyll a to b ratio, chlorophyll a fluorescence, photosynthetic activity, carbohydrates and RuBisCO both subunits content. NO-dependent biochemical alterations were linked to cytological observation of developing plastids in cotyledons of apple plants. Abnormal plantlets developing from dormant apple embryos are characterized by anatomical malformations of cotyledons. Short-term pre-treatment with NO of isolated embryos or seedlings with developmental anomalies resulted in formation of plants with cotyledons of equal size and chlorophyll content; these responses were blocked by NO scavenger. NO independently of time point of application accelerated embryos transition from heterotrophy to autotrophy by stimulation of photosynthetic activity, improvement of parameters of chlorophyll a fluorescence (Fv/Fm, Fv/F0) and increased content of RuBisCO small subunit. Further analysis showed that NO application modified glucose and hydrogen peroxide concentration in cotyledons. Beneficial effect of NO on development of seedlings without any abnormalities was manifested at ultrastructural level by decline in amount of proplastids and induction of formation and maturation of chloroplasts. Our data suggest that progress of autotrophy of young seedlings is governed by NO acting as stimulator of chloroplast-to-nucleus signaling.

Objectives Multiple studies have suggested that women have worse outcomes than men following mitral valve surgery—most of those studies reported on conventional sternotomy mitral valve surgery (CS). Therefore, we aimed to explore whether or not the minimally invasive mitral valve surgery (MIMVS) approach might mitigate a worse survival in women following CS. Methods We identified patients with isolated primary mitral valve operations with or without tricuspid valve repair performed between 2007 and 2019. Patients were propensity score-matched across the MIMVS and CS surgical approaches. Sex was excluded from the matching process to discern whether female patients have a different likelihood of receiving minimally invasive surgery than males. A Cox proportional hazards model was fitted in the matched cohort and adjusted for the imbalance in baseline characteristics using the propensity score. Results Of 956 patients (417 MIMVS, 539 CS; 424 females), the matched set comprised 342 pairs (684 patients; 296 females) of patients who were well balanced across MIMVS and CS groups with regard to preoperative clinical characteristics. We observed a 47/53% female/male ratio in the CS and a 39/61% in the MIMVS group, p = 0.054. In both matched groups, women were older than males. A Cox model adjusted for propensity scores showed no survival difference with sex, surgical type, or interaction. Conclusions Women present to the surgical team at an older age. They appear to be less likely to be considered for a MIMVS approach than men. Neither sex nor surgical approach was associated with survival in a matched sample.