ABSTRACT
Date fruits vary widely in the hardness of their edible parts and they are classified accordingly into soft, semi-dry, and dry varieties. Fruit texture, a significant parameter in determining consumer acceptance, is related to the tissue structure and chemical composition of the fruit, mainly the ratio of sucrose to reducing sugars. This study aimed to understand the relationship between the chemical composition, microstructure, and texture profile of 10 major Emirati date fruits. The soluble sugars, glucose and fructose, represent ca 80 g/100 g of the fruits on the basis of dry weight (DW) while the dietary fiber contents varied 5.2-7.4 g/100 dg D.W. with lignin being the main determinant of the variability. The textures of the samples were studied using instrumental texture profile analysis. While no correlation was found between the soluble sugar and texture parameters in this study, the different fiber constituents correlated variably with the different parameters of date fruit texture. Lignin, arabinoxylan, galactomannan, and pectin were found to correlate significantly with fruit hardness and the related parameters, gumminess and chewiness. Both lignin and arabinoxylan correlated with resilience, and arabinoxylan exhibited a strong correlation with cohesiveness.
Subject(s)
Dietary Fiber/analysis , Hardness , Phoeniceae/chemistry , Phoeniceae/classification , Fructose/analysis , Galactose/analogs & derivatives , Glucose/analysis , Lignin/analysis , Mannans/analysis , Microscopy , Pectins/analysis , Phoeniceae/ultrastructure , Sucrose/analysis , Xylans/analysisABSTRACT
Date palm rachis fibers are rich in cellulose, relatively inexpensive, and readily available in Algeria. The aim of this study is to investigate the morphology, structure, mechanical and physicochemical characteristics of both vascular bundles and fiber strands extracted from date palm rachis. The difficulties encountered are associated to the extraction of the fibers without damaging them. The study focuses on the morphological and surface roughness analysis using optical and scanning electron microscopies (SEM), and a non-contact 3D profiler. The chemical, physical and thermal properties have been studied using Fourier-transform infrared (FTIR) spectroscopy, energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The mechanical properties were accessed by tensile tests and they were analyzed using two-parameter Weibull distribution.
Subject(s)
Phoeniceae/chemistry , Plant Vascular Bundle/chemistry , Cellulose/chemistry , Phoeniceae/ultrastructure , Plant Components, Aerial/chemistry , Plant Components, Aerial/ultrastructure , Plant Vascular Bundle/ultrastructure , Polysaccharides/chemistry , Surface Properties , Tensile StrengthABSTRACT
The efficacy of the cuticular transpiration barrier and its resistance to elevated temperatures are significantly higher in a typical water-saver than in a water-spender plant growing in hot desert.
Subject(s)
Citrullus colocynthis/physiology , Phoeniceae/physiology , Plant Transpiration , Water/metabolism , Citrullus colocynthis/ultrastructure , Microscopy, Electron, Scanning , Phoeniceae/ultrastructure , Plant Leaves/physiology , Plant Leaves/ultrastructure , TemperatureABSTRACT
Date palm Phoenix dactylifera is a desert crop well adapted to survive and produce fruits under extreme drought and heat. How are palms under such harsh environmental conditions able to limit transpirational water loss? Here, we analysed the cuticular waxes, stomata structure and function, and molecular biology of guard cells from P. dactylifera. To understand the stomatal response to the water stress phytohormone of the desert plant, we cloned the major elements necessary for guard cell fast abscisic acid (ABA) signalling and reconstituted this ABA signalosome in Xenopus oocytes. The PhoenixSLAC1-type anion channel is regulated by ABA kinase PdOST1. Energy-dispersive X-ray analysis (EDXA) demonstrated that date palm guard cells release chloride during stomatal closure. However, in Cl- medium, PdOST1 did not activate the desert plant anion channel PdSLAC1 per se. Only when nitrate was present at the extracellular face of the anion channel did the OST1-gated PdSLAC1 open, thus enabling chloride release. In the presence of nitrate, ABA enhanced and accelerated stomatal closure. Our findings indicate that, in date palm, the guard cell osmotic motor driving stomatal closure uses nitrate as the signal to open the major anion channel SLAC1. This initiates guard cell depolarization and the release of anions together with potassium.
