Storage Stability Of Seeds Research Articles

Non-Destructive Direct Pericarp Thickness Measurement of Sorghum Kernels Using Extended-Focus Optical Coherence Microscopy

Non-destructive measurements of internal morphological structures in plant materials such as seeds are of high interest in agricultural research. The estimation of pericarp thickness is important to understand the grain quality and storage stability of seeds and can play a crucial role in improving crop yield. In this study, we demonstrate the applicability of fiber-based Bessel beam Fourier domain (FD) optical coherence microscopy (OCM) with a nearly constant high lateral resolution maintained at over ~400 µm for direct non-invasive measurement of the pericarp thickness of two different sorghum genotypes. Whereas measurements based on axial profiles need additional knowledge of the pericarp refractive index, en-face views allow for direct distance measurements. We directly determine pericarp thickness from lateral sections with a 3 µm resolution by taking the width of the signal corresponding to the pericarp at the 1/e threshold. These measurements enable differentiation of the two genotypes with 100% accuracy. We find that trading image resolution for acquisition speed and view size reduces the classification accuracy. Average pericarp thicknesses of 74 µm (thick phenotype) and 43 µm (thin phenotype) are obtained from high-resolution lateral sections, and are in good agreement with previously reported measurements of the same genotypes. Extracting the morphological features of plant seeds using Bessel beam FD-OCM is expected to provide valuable information to the food processing industry and plant breeding programs.

RNAi mediated silencing of lipoxygenase gene to maintain rice grain quality and viability during storage

Lipoxygenase (LOX) is a common enzyme which catalyzes lipid peroxidation of seeds and consequently enhances seed quality deterioration and decreases seed viability. During seed storage, peroxidation of unsaturated fatty acids occur due to enhancement of LOX activity which directly leads to reduction in seed vigour and deterioration of grain nutritional quality. This study was undertaken to overcome these problem during rice seed storage by attenuating LOX activity using RNAi technology. To improve seed storage stability, we down regulated LOX gene activity by using a functional fragment of the LOX gene under the control of both constitutive (CaMV35S) and aleurone-specific (Oleosin-18) promoter separately. To understand the storage stability, RNAi–LOX seeds and non-transgenic control seeds were subjected to accelerated aging at 45 °C and 85 % relative humidity for 14 days. Our studies demonstrate that down regulation of LOX activity reduces the seed quality deterioration under storage condition. In addition GC–MS analysis revealed that reduction of fatty acid level in non-transgenic seeds during storage was higher when compared with that of transgenic rice seeds. Furthermore, the transgenic rice seeds with reduced LOX activity exhibited enhanced seed germination efficiency after storage than that of non-transgenic rice seeds. This study will have direct impact on nutritional stability of quality rice grains.

Variability in oil content and composition and storage stability of seeds from Jatropha curcas L. grown in Mozambique

This study evaluates the variation in oil content and composition of Jatropha curcas L. seeds from 12 origins, grown in Mozambique, under the same edapho-climatic and agronomic conditions. The seeds had oil contents from 37% to 45% (d.w.). The oils were rich in oleic (mean 40%) and linoleic (mean 40%) acids and poor in linolenic acid (mean 0.22%), with high content of beta-sitosterol (71% of total sterols), low acidity and low levels of oxidation products, making them adequate for biodiesel production by alkaline-catalyzed transesterification.The high levels of gamma-tocopherol (69–182mg/kg) may explain the high oxidative stability exhibited by the oil during 6 months of storage at 28 or 35°C. Conversely, seeds storage under high temperatures and humidity promoted the growth of fungi responsible for oil degradation. Therefore, under tropical climate conditions, when oil conversion to biodiesel is not possible immediately after fruit harvest, it is better to extract the oil and store it under closed containers without contact with oxygen and light, to preserve its quality, than to store the seeds.

Intracellular glasses and seed survival in the dry state

So-called orthodox seeds can resist complete desiccation and survive the dry state for extended periods of time. During drying, the cellular viscosity increases dramatically and in the dry state, the cytoplasm transforms into a glassy state. The formation of intracellular glasses is indispensable to survive the dry state. Indeed, the storage stability of seeds is related to the packing density and molecular mobility of the intracellular glass, suggesting that the physico-chemical properties of intracellular glasses provide stability for long-term survival. Whereas seeds contain large amounts of soluble non-reducing sugars, which are known to be good glass formers, detailed in vivo measurements using techniques such as FTIR and EPR spectroscopy reveal that these intracellular glasses have properties that are quite different from those of simple sugar glasses. Intracellular glasses exhibit slow molecular mobility and a high molecular packing, resembling glasses made of mixtures of sugars with proteins, which potentially interact with additional cytoplasmic components such as salts, organic acids and amino acids. Above the glass transition temperature, the cytoplasm of biological systems still exhibits a low molecular mobility and a high stability, which serves as an ecological advantage, keeping the seeds stable under adverse conditions of temperature or water content that bring the tissues out of the glassy state. To cite this article: J. Buitink, O. Leprince, C. R. Biologies 331 (2008).

Glass formation in plant anhydrobiotes: survival in the dry state*1

Anhydrobiotes can resist complete dehydration and survive the dry state for extended periods of time. During drying, cytoplasmic viscosity increases dramatically and in the dry state, the cytoplasm transforms into a glassy state. Plant anhydrobiotes possess large amounts of soluble non-reducing sugars and their state diagrams resemble those of simple sugar mixtures. However, more detailed in vivo measurements using techniques such as Fourier transform infrared spectroscopy and electron paramagnetic resonance spectroscopy reveal that these intracellular glasses are complex systems with properties quite different from those of simple sugar glasses. Intracellular glasses exhibit a high molecular packing and slow molecular mobility, resembling glasses made of mixtures of proteins and sugars, which potentially interact with additional cytoplasmic components such as salts, organic acids, and amino acids. Above the glass transition temperature, the cytoplasm of biological systems still exhibits a high stability and low molecular mobility, which could serve as an ecological advantage. All desiccation-tolerant organisms form glasses upon drying, but desiccation-sensitive organisms generally lose their viability during drying at water contents at which the glassy state has not yet been formed, suggesting that other factors are necessary for desiccation tolerance. Nevertheless, the formation of intracellular glasses is indispensable to survive the dry state. Storage stability of seeds and pollens is related to the molecular mobility and packing density of the intracellular glass, suggesting that the characteristic properties of intracellular glasses provide stability for long-term survival.

Molecular mobility in the cytoplasm of lettuce radicles correlates with longevity

AbstractMolecular mobility is hypothesised to be a key factor influencing storage stability of seeds because it may control the rate of deteriorative reactions responsible for reduced shelf life. The relationship between the longevity of lettuce seeds and the molecular mobility was investigated in the cytoplasm of lettuce radicles. Longevity of lettuce seeds was predicted using the viability equation of Ellis and Roberts, and the molecular mobility was determined by saturation transfer electron paramagnetic resonance spectroscopy measurements of rotational motion of a polar spin probe inserted into the cytoplasm. Increasing the temperature resulted in faster rotational motion and shorter longevity. There was a linear relationship between the logarithms of rotational motion and estimated seed longevity for temperatures above 5°C. Below 5°C, there was a deviation from linearity. Based on the hypothesis that the molecular mobility in the cytoplasm determines the rate of detrimental reactions, seed longevity at sub-zero temperatures was predicted by extrapolation of the rotational motion using the linear relationship. Predictions of longevity at sub-zero temperatures based on rotational motion indicated longer survival times than those based on the viability equation. A kinetic approach to ageing using molecular mobility measurements is expected to improve our understanding of seed storage stability and might eventually lead to realistic predictions of longevity at low temperatures.

Glassy State and Seed Storage Stability: The WLF Kinetics of Seed Viability Loss at T>Tgand the Plasticization Effect of Water on Storage Stability

The relationship between the glassy state in seeds and storage stability was examined, using the glass transition curve and a seed viability database from previous experiments. Storage data for seeds at various water contents were studied by Williams–Landel–Ferry (WLF) kinetics, whereas the glass transition curves of seeds with different storage stability were analysed by the Gordon–Taylor equation in terms of the plasticization effect of water on seed storage stability. It was found that the critical temperatures (T c ) for long-term storage of three orthodox seeds were near or below their glass transition temperatures (T g ), indicating the requirement for the presence of the glassy state for long-term seed storage. The rate of seed viability loss was a function of T-T g at T>T g , which fitted the WLF equation well, suggesting that storage stability was associated with the glass transition, and that the effect of water content on seed storage was correlated with the plasticization effect of water on intracellular glasses. A preliminary examination suggested a possible link between the glass transition curve and seed storage stability. According to the determined WLF constants, intracellular glasses in seeds fell into the second class of amorphous systems as defined by Slade and Levine ( Critical Reviews in Food Science and Nutrition30 : 115–360, 1991). These results support the interpretation that the glassy state plays an important role in storage stability and should be a major consideration in optimizing storage conditions.

A Calorimetric Study of the Glass Transition Behaviors in Axes of Bean Seeds with Relevance to Storage Stability.

Although the presence of intracellular aqueous glasses has been established in seeds, their physiological role in storage stability is still conjectural. Therefore, we examined, using differential scanning calorimetry, the thermal behavior of glass transitions in axes of bean (Phaseolus vulgaris L.) with water contents (WC) between 0 and 1 g H2O/g dry weight (g/g) and temperatures between -120 and +120[deg]C. Three types of thermal behaviors associated with the glass transition were observed. The appearance, the glass -> liquid transition temperature, and the amount of energy released during these transitions were dependent on the tissue WC. No glass transitions were observed at WC lower than 0.03 and higher than 0.45 g/g. A brief exposure to 100[deg]C altered the glass properties of tissues with WC between 0.03 and 0.08 g/g but did not affect the thermal behavior of glasses with higher WC, demonstrating that thermal history is important to the intracellular glass behavior at lower WC. Correspondence of data from bean to models predicting the effects of glass components on the glass -> liquid transition temperature suggests that the intracellular glasses are composed of a highly complex sugar matrix, in which sugar and water molecules interact together and influence the glass properties. Our data provide evidence that additional glass properties must be characterized to understand the implications of a glassy state in storage stability of seeds.

Glassy State and Seed Storage Stability: A Viability Equation Analysis

Dry seeds exist generally in a glassy (or vitrified) state. The high viscosity of the glassy state would be expected to have a retarding effect on deteriorative reactions in the cytoplasm. Thus the glassy state may be considered to be a biophysical barrier for seed deterioration. The present study aims to test the hypothesis that seed storage stability is associated with the glassy state. With the equations derived from the seed viability equation, we have calculated the maximum temperature (Tmax) for long-term storage of corn, pea and soybeans. The Tmax for long-term seed storage is found to be in a good agreement with the glass transition temperature (Tg) in each instance, suggesting that seed deterioration would be accelerated when seeds are not in the glassy state. Experiments with soybeans given accelerated ageing show that the loss of glassy state is followed by a rapid decrease in seed viability. These observations provide indirect evidence that the glassy state may play a significant role in seed storage stability.

Methods for Determination of Glass Transitions in Seeds

When the non-freezeable (bound, amorphous, vitreous) water of pea or soybean embryos is examined by dielectric methods, three state transitions can be observed. The lowest occurs at the glass transition temperature (Tg) of pure amorphous water, is invariant with water content and is probably associated with crystal defects and other interfaces. The second, at about -60°C, is dependent upon water content and probably reflects rotational mobility of side chains (β-transition). It can be seen by dynamic mechanical analysis (DMA) as well, but the energies are too small to detect by differential scanning calorimetry (DSC). The third is the glass transition, which reflects the increase in diffusional mobility in the sample. The increase in fluidity can be measured by DMA and the increase in heat capacity of water is detectable by DSC. This is the transition that has been associated with changes in seed storage stability. Heretofore, DSC has been the method of choice because of its availability, familiarity and its ease of operation and interpretation. However, at low sample water contents, DSC signals become small and diffuse and the assignment of Tg becomes difficult. Because DMA is the most sensitive to local motion, it provides the most credible information on changes in sample viscosity that occur during glass transition. We have recently examined embryos in the Perkin-Elmer DMA-7 and found that DMA provides richer data for these studies than does DSC.

Glassy states in dormant corn embryos

Corn embryos contain oils with two melting points and a strong tendency to form glasses at temperatures down to −95° When these were extracted, water : sugar glasses can also be detected, with the water serving as a plasticizer. When the water content drops below about 12% (the water content required for seed storage stability) the transition temperature of these water glasses rises above ambient. These data are consistent with our hypothesis that the dormant state in these seeds is a glassy state.