Brazilian Journal of Botany最新文献

The structural diversity of pollinia is one of the most relevant characters for the species classification in Orchidaceae. In this study, we analyzed the development of the pollinia and caudicle in Epidendrum species belonging to the subgenus Amphyglottium, one of the groups with the most variable morphology of the genus. These species have different pollination strategies (e.g., presence vs. absence of nectar) and grow in different types of habitat. Floral buds and flowers at anthesis were collected, and the usual methodology for performing anatomical studies, scanning microscopy, and confocal microscopy following established protocols. Our investigations revealed that the studied species have bithecal anthers and each theca has two pollinia and two caudicles. No interspecific variation was observed regarding the formation of the male gametophyte, indicating that is a stable character for the genus: the archesporial cells undergo a meiotic process that originates microspores, which remain united in tetrad and pass through asymmetric mitosis to form viable pollen grains. The caudicle is of the appendicular type and shows the male gametophyte formation.

The purpose of this research was to examine the impacts of varying levels of Ca concentrations (0, 5, and 10 mM) on mint plants (Mentha longifolia L.) cultivated hydroponically, specifically under conditions of zinc (Zn) toxicity (300, and 600 μM). Various aspects, including chlorophyll and proline metabolisms, defense mechanisms (antioxidant and glyoxalase systems), ion balance, and sulfur assimilation process, were examined to assess the effects. Zn treatment resulted in the initiation of oxidative stress, hindered nutrient absorption, and led to an increase in Zn leaf concentration. These effects together contributed to the impairment of the photosynthesis apparatus and a subsequent decrease in the growth of mint seedlings. However, adding Ca by modulating proline and chlorophyll metabolisms raised proline and chlorophyll levels. Ca treatment (especially 10 mM) reduced methylglyoxal (31.1 and 38%), malondialdehyde (44.9 and 42.1%), and hydrogen peroxide (31.2 and 48.5%) levels and electrolyte leakage (22 and 30.6%) in Zn-stressed plants by strengthening the antioxidant machinery. The application of Ca by attenuating Zn amount and facilitating the uptake of mineral nutrients maintained the ionic balance under Zn toxicity. Ca addition resulted in the upregulation of enzymes associated with the sulfur metabolism, leading to elevated amounts of cysteine, glutathione, and phytochelatins. Therefore, our findings point out that Ca increased the adaptation of mint seedlings during Zn phytotoxicity by modulating proline and chlorophyll metabolism, reinforcing the antioxidant capacity, maintaining ionic homeostasis, and inducing the sulfur assimilation mechanism.

Strigolactones (SLs) are carotenoid-derived terpenoid lactones. Natural SLs are grouped into two types, namely, strigol-type and orobanchol-type, and 20 SLs have been identified from different plant kingdoms or species. The more stable SLs, called GR24, derived synthetically, were utilized for the investigation of SL responses. SLs are crucial endogenous plant hormones that play a multifactorial role in plant and rhizosphere interactions by controlling mycorrhization and lateral shoot branching. SLs participate in the organization of plant architecture by reducing bud outgrowth in addition to various morphological and developmental processes, collectively with other plant growth hormones such as auxins, cytokinins, gibberellins, and abscisic acid. Strigolactones regulate root growth and structure by inhibiting lateral root production and enhancing root hair elongation. Targeted genetic engineering of SL biosynthetic genes leads to potential alterations in rooting and vegetative systems and assists in generating plants that are more appropriate to different adverse environmental conditions, such as drought, salt stress, cold, and water deficit. The present review provides a clear outline of the structure, type, biosynthesis, and signaling mechanisms of SLs. In addition, their potential functions in plant growth, development, and response to stress conditions are also discussed.

In order to clarify the characteristics of the chloroplast (cp) genome of Vaccinium ashei Reade cv. ‘brightwell’ and understand its phylogenetic status, the whole cp genome of this sepcies was sequenced and assembled, and its genome structure, gene composition, and signs of adaptation were analyzed. The cp genome has a quadripartite structure with a size of 176,115 bp and a total GC content of 36.81%. The length of large single copy (LSC) region, small single copy (SSC) region and two inverted repeat (IR) regions was 106,029 bp, 3004 bp, and 33,541 bp, respectively. It has a total of 103 genes, containing 74 protein-coding genes, 25 tRNA genes and 4 rRNA genes. A total of 187 SSR sites were observed, with the largest number of mononucleotides in the repeat type, accounting for 72% of the total. By comparing with related Vaccinium genotypes, 25 single nucleotide polymorphisms (SNPs) and 35 insertion/deletions (Indels) were identified. Highly variable regions such as trnM-psaI, trnD-psbM, psbJ-psbB, psaA-trnQ, clpP-rpoA, rpl36-rps8, rpl16-rps3, and trnM-trnL intergenic spacers may be used as candidate markers for intraspecific differentiation. The Ka/Ks calculations showed that the two genes (psbJ and psbT) were strongly positively selected. Phylogenetic results reflected that the Vaccinium genus was clustered into two clades, and V. ashei was more closely related to V. uliginosum. These results provide a reference for the development of molecular markers, phylogeny, cp genome evolution and variety breeding of Vaccinium.