Effects of leaf and stem maturation on nutritional value in Megathyrsus maximus.

BACKGROUND: Megathyrsus maximus is a forage grass native to Africa but widely cultivated in tropical and subtropical regions of the world where it is part of the grazing food chain. This study aimed to evaluate five M. maximus genotypes for the effect of maturity on their morpho-agronomic traits, nutritional composition and digestibility, and to correlate their leaf blade and stem anatomy with their nutritional value. RESULTS: The proportion of sclerenchyma tissues increased as maturity was reached, while lignin accumulation was differentiated between genotypes. Gatton Panic, Green Panic and Mutale genotypes maintained their acid detergent lignin (ADL) values for leaf blades in the three cuts evaluated. In sacco ruminal dry matter disappearance was lower in Green Panic genotype at the vegetative stage for stems, but not for leaf blades. Significant positive correlations were found between dry matter disappearance and mesophyll tissues, and the latter were negatively correlated with neutral detergent fiber (NDF) and ADL. CONCLUSION: Our results strongly indicate that cutting age and genotype affected the nutritional value of M. maximus leaf blades and stems, with a more pronounced loss of quality in stems than in leaf blades. We recommend increasing the frequency of grazing at early stage or anticipating the stage of stem elongation in Green Panic to produce forage with better nutritional value. © 2023 Society of Chemical Industry.

Structural and histochemical approach to the fruit and seed diversity of Cyperaceae in an evolutionary context.

KEY MESSAGE: The Cyperaceae fruit consistency depends on the mesocarp. Seed structure is diverse and related to the evolutionary history of their species. A new storage tissue is described for Cyperaceae. Anatomy and histochemistry of Cyperaceae fruits (including seeds) are poorly known due to their hard, isolating tissues that prevent anatomical techniques. We performed the first, most comprehensive structural diversity characterisation of fruit and seed in Cyperaceae, accompanied by an unprecedented histochemical characterisation of seeds for this family. We analysed fruits of 29 species, included in 19 genera and 12 tribes within the subfamilies Cyperoideae and Mapanioideae, using light microscopy. Cyperaceae fruits have a pericarp with a one-cell-layered exocarp and endocarp, and a multi-cell-layered mesocarp. The mesocarp of the Mapanioideae has a spongy-fleshy outer region and a hard inner region. The mesocarp of the Cyperoideae has only a hard region. The pericarp is free from the seed coat. Cyperaceae seeds have a three-layered seed coat, an embryo with haustorial function of its scutellum, and two storage tissues: the endosperm and a putative perisperm. Nine seed morphotypes and four seed subtypes were observed among the studied species. Our results suggested that the fruit consistency is determined by the mesocarp. Both the terms "nut" and "achene" should be accepted to refer to the dry fruit of the Cyperaceae until a widely accepted fruit classification for angiosperms is proposed. The Cyperaceae seed structural diversity is high and related to the evolutionary history of the species. The "perisperm" is a new tissue proposed for sedge seeds, and is here characterized for the first time. The seed coat has a different structure than the one described so far for the family.