Análises anatômicas e ultraestruturais em folhas de Mimosa (Leguminosae) com diferentes tipos de movimento foliar e influência do cálcio em aspectos estruturais e funcionais dos pulvinos
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Data
2023-02-27
Autores
Silva, Stefany Cristina de Melo
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Universidade Estadual Paulista (Unesp)
Resumo
Leguminosas são caracterizadas pela presença de pulvinos que garantem às folhas capacidade de movimentação em resposta à estímulos endógenos ou exógenos. O funcionamento dos pulvinos está relacionado com mudanças na pressão de turgor e alterações na conformação do citoesqueleto nas células corticais (células motoras), o que envolve proteínas cálcio-dependentes, além das características do sistema vascular, especialmente do floema. Estudos demonstram que pulvinos de folhas com movimentos lentos apresentam cristais prismáticos de oxalato de cálcio na endoderme, enquanto que pulvinos de espécies com movimentos rápidos apresentam endoderme desprovida de cristais. Este trabalho teve como objetivo investigar aspectos anatômicos e ultraestruturais de pulvinos e pecíolos de forma comparativa entre espécies de Mimosa com diferentes tipos de movimento foliar com ênfase nas características subcelulares do floema, além de averiguar se a disponibilidade de cálcio influencia na formação de cristais na endoderme e no funcionamento dos pulvinos. Indivíduos de Mimosa caesalpiniifolia Benth., espécie com movimentos foliares nictinásticos lentos, e Mimosa pudica L., espécie com movimentos foliares seismonásticos rápidos, foram submetidos a 360, 240, 120 e 0 mgL-1 de Ca2+ em meio hidropônico. Pulvinos e pecíolos foram processados segundo técnicas convencionais em microscopia de luz e eletrônica de varredura (MEV) e transmissão (MET). Análises utilizando espectroscopia por energia dispersiva foram realizadas ao MEV para quantificação de cálcio; técnica ultracitoquímica foi aplicada para localização de depósitos subcelulares de cálcio ao MET. Os pulvinos de M. caesalpiniifolia apresentam características comumente encontradas em outras espécies de leguminosas, incluindo espécies de Mimosa com movimentos foliares rápidos. Embora seja um aspecto comum para pulvinos com movimentos lentos, a detecção de cristais de oxalato de cálcio na endoderme é uma novidade para pulvinos de Mimosa, corroborando a ideia de que o conteúdo da endoderme dos pulvinos está relacionado ao tipo de movimento foliar apresentado. Proteínas filamentosas, tubulares e corpos paracristalinos foram observados nos elementos de tubo crivado de pulvinos e pecíolos de ambas as espécies, sendo que a abundância de proteína-P pareceu ser maior nos pulvinos que nos pecíolos, o que pode estar relacionado ao envolvimento do floema no funcionamento dos pulvinos. Nos pulvinos e pecíolos de M. pudica, o acúmulo de proteína-P pareceu ser maior que em M. caesalpiniifolia, o que parece ter relação com o tipo de movimento foliar apresentado. Além disso, a abundância de proteína-P no pecíolo de M. pudica sugere o papel do floema peciolar na transmissão basípeta de estímulos dos folíolos para o pulvino. As paredes dos elementos de tubo crivado se mostraram mais espessas nos pulvinos em comparação com pecíolo, especialmente em M. pudica, sugerindo seu envolvimento no transporte radial de íons durante a movimentação foliar. Cristais prismáticos de oxalato de cálcio se formaram na endoderme de pulvinos e pecíolos de M. caesalpiniifolia em todos os tratamentos, exceto na ausência de Ca2+. Nos pulvinos de M. pudica não houve formação de cristais de oxalato de cálcio em nenhum dos tratamentos; por outro lado, nos pecíolos dessa espécie, cristais foram formados em todos os tratamentos, exceto na ausência de cálcio. Em M. caesalpiniifolia, as folhas apresentaram movimentos nictinásticos lentos em todos os tratamentos, inclusive na ausência de cálcio. Plantas de M. pudica mantiveram sua capacidade de movimentação foliar em resposta a estímulos mecânicos, exceto na ausência de Ca2+. Nossos resultados sugerem o maior envolvimento do cálcio nos mecanismos de funcionamento e reações celulares em pulvinos de folhas com movimentos seismonásticos rápidos em comparação com pulvinos de folhas com movimentos foliares nictinásticos lentos.
Legumes are characterized by the presence of pulvini guarantee the ability of leaves to move in response to endogenous or exogenous stimuli. The functioning of the pulvini is related to changes in the turgor pressure and changes in the conformation of the cytoskeleton in the cortical cells (motor cells), which involves calcium-dependent proteins, in addition to the characteristics of the vascular system, especially the phloem. Studies show that pulvini from leaves with slow movements have prismatic crystals of calcium oxalate in the endodermis, while pulvini from species with fast movements have endoderm devoid of crystals. Aspects of pulvini and petioles in a comparative way between Mimosa species with different types of leaf movement with emphasis on the subcellular characteristics of the phloem, in addition to investigating whether the availability of calcium influences the formation of crystals in the endoderm and in the functioning of the pulvini. Individuals of Mimosa caesalpiniifolia Benth., a species with slow nyctinastic leaf movements, and Mimosa pudica L., a species with fast seismonastic leaf movements, were submitted to 360, 240, 120 and 0 mgL-1 of Ca2+ in hydroponic solution. Pulvini and petioles were processed according to conventional techniques in light and scanning electron (SEM) and transmission (TEM) microscopy. Analyzes using energy dispersive spectroscopy were performed under SEM for calcium quantification; The ultracytochemical technique was applied to localize subcellular calcium deposits to TEM. Pulvini of M. caesalpiniifolia exhibit features commonly found in other legume species, including Mimosa species with rapid leaf movements. Although it is a common aspect for pulvini with slow movements, the detection of calcium oxalate crystals in the endodermis is a novelty for pulvini of Mimosa, corroborating the idea that the content of the endodermis of pulvini is related to the type of leaf movement presented. Filamentous, tubular proteins and paracrystalline bodies were observed in the sieve tube elements of pulvini and petioles of both species, and the abundance of P-protein appeared to be greater in pulvini than in petioles, which may be related to the involvement of the phloem in the pulvini functioning. In the pulvini and petioles of M. pudica, the accumulation of Pprotein seemed to be greater than in M. caesalpiniifolia, which seems to be related to the type of leaf movement presented. Furthermore, the abundance of P-protein in the petiole of M. pudica suggests the role of the petiolar phloem in the basipetal transmission of stimuli from the leaflets to the pulvinus. The walls of sieve-tube elements were thicker in pulvini compared to petioles, especially in M. pudica, suggesting their involvement in radial ion transport during leaf movement. Prismatic crystals of calcium oxalate formed in the endodermis of pulvini and petioles of M. caesalpiniifolia in all treatments, except in the absence of Ca2+. In M. pudica pulvinus there was no formation of calcium oxalate crystals in any of the treatments; on the other hand, in the petioles of this species, crystals were formed in all treatments, except in the absence of calcium. In M. caesalpiniifolia, the leaves showed slow nyctinastic movements in all treatments, even in the absence of calcium. M. pudica plants maintained their leaf movement capacity in response to mechanical stimuli, except in the absence of Ca2+. Our results suggest a greater involvement of calcium in the functioning mechanisms and cellular reactions in leaf pulvini with fast seismonastic movements compared to leaf pulvini with slow nyctinastic leaf movements.
Legumes are characterized by the presence of pulvini guarantee the ability of leaves to move in response to endogenous or exogenous stimuli. The functioning of the pulvini is related to changes in the turgor pressure and changes in the conformation of the cytoskeleton in the cortical cells (motor cells), which involves calcium-dependent proteins, in addition to the characteristics of the vascular system, especially the phloem. Studies show that pulvini from leaves with slow movements have prismatic crystals of calcium oxalate in the endodermis, while pulvini from species with fast movements have endoderm devoid of crystals. Aspects of pulvini and petioles in a comparative way between Mimosa species with different types of leaf movement with emphasis on the subcellular characteristics of the phloem, in addition to investigating whether the availability of calcium influences the formation of crystals in the endoderm and in the functioning of the pulvini. Individuals of Mimosa caesalpiniifolia Benth., a species with slow nyctinastic leaf movements, and Mimosa pudica L., a species with fast seismonastic leaf movements, were submitted to 360, 240, 120 and 0 mgL-1 of Ca2+ in hydroponic solution. Pulvini and petioles were processed according to conventional techniques in light and scanning electron (SEM) and transmission (TEM) microscopy. Analyzes using energy dispersive spectroscopy were performed under SEM for calcium quantification; The ultracytochemical technique was applied to localize subcellular calcium deposits to TEM. Pulvini of M. caesalpiniifolia exhibit features commonly found in other legume species, including Mimosa species with rapid leaf movements. Although it is a common aspect for pulvini with slow movements, the detection of calcium oxalate crystals in the endodermis is a novelty for pulvini of Mimosa, corroborating the idea that the content of the endodermis of pulvini is related to the type of leaf movement presented. Filamentous, tubular proteins and paracrystalline bodies were observed in the sieve tube elements of pulvini and petioles of both species, and the abundance of P-protein appeared to be greater in pulvini than in petioles, which may be related to the involvement of the phloem in the pulvini functioning. In the pulvini and petioles of M. pudica, the accumulation of Pprotein seemed to be greater than in M. caesalpiniifolia, which seems to be related to the type of leaf movement presented. Furthermore, the abundance of P-protein in the petiole of M. pudica suggests the role of the petiolar phloem in the basipetal transmission of stimuli from the leaflets to the pulvinus. The walls of sieve-tube elements were thicker in pulvini compared to petioles, especially in M. pudica, suggesting their involvement in radial ion transport during leaf movement. Prismatic crystals of calcium oxalate formed in the endodermis of pulvini and petioles of M. caesalpiniifolia in all treatments, except in the absence of Ca2+. In M. pudica pulvinus there was no formation of calcium oxalate crystals in any of the treatments; on the other hand, in the petioles of this species, crystals were formed in all treatments, except in the absence of calcium. In M. caesalpiniifolia, the leaves showed slow nyctinastic movements in all treatments, even in the absence of calcium. M. pudica plants maintained their leaf movement capacity in response to mechanical stimuli, except in the absence of Ca2+. Our results suggest a greater involvement of calcium in the functioning mechanisms and cellular reactions in leaf pulvini with fast seismonastic movements compared to leaf pulvini with slow nyctinastic leaf movements.
Descrição
Palavras-chave
Cristais de oxalato de cálcio, Elemento de tubo crivado, Endoderme, Pecíolo, Pulvino, Proteína-P, Calcium oxalate crystals, Endodermis, P-protein, Petiole, Pulvinus, Sieve tube members