Storage of Amaranth Seeds: Reflex in Physiologic Potential

The aimed to evaluate the effect of packages and different environment conditions in the maintenance of physiologic quality of Amaranthus cruentus seeds in the period of 300 days. The seeds used were from the cultivar BRS Alegria indicated for use in Brazilian winter. The experimental design completely randomized in factorial scheme (storage environment × package type × storage period) with four replicates. The amaranth seeds storage in plastic packages, in refrigerator and cold chamber, resulted in better germination maintenance ability. The conditioning in PET package, in natural and cold chamber environments promoted better results in relation to germination. The storage period did not present significant effect for the seeds stored in refrigerator and PET, although, for paper package there was reduction. The amaranth seeds, cv. BRS Alegria, can be stored in cold chamber for until 300 days, conditioned in PET, without reduction of its physiologic potential.

The seeds spend internal reserves, causing mass loss and drastic decrease in germination (Carvalho, Nakagawa, 2012).
Seed quality is basically determined by their physiological potential, which gathers information on viability and vigor of a seed lot, with the potential term translated as virtuality or set of skills to perform tasks and produce results (Marcos Filho, 2005).
When speaking of maintaining the physiologic quality during the storage, the package is of fundamental importance. The package types used to store may directly affect the quality, avoiding or not the humidity exchange between the seeds and environment (Medeiros & Zanon, 2000). The main function of seeds package is to lag its deterioration by reducing respiration (Tonin & Perez, 2006).
In this manner, the modern conservation techniques allow only to prolong the utile life of the seeds during storage (Silva et al., 2015). According to the exposed and facing the importance of the study of amaranth seeds during storage, this study aimed to evaluate the effect of packages and different environment conditions in the maintenance of physiologic quality of Amaranthuscruentus seeds in the period of 300 days.

Material and Methods
The amaranth seeds were obtained in experiment carried out in Experimental Field of the Plant Science Department of the EliseuMaciel Agronomy College, from the Federal University of Pelotas, in the city of Capão do Leão (31°46′3″ Southern, longitude: 52°26′55″ and altitude of 30 m) in the state of Rio Grande do Sul, Brazil, in the crop season of 2013. The region climate, according to Köppen and Geiger (1928), is Cfa type. The average temperature and rainfall were 18 ºC and 1378 mm, respectively. The soil is classified as albaqualf soil (Embrapa-Cnps, 2006).
The seeds used were from the cultivar BRS Alegria, of the EmbrapaProdutos de Mercado germplasm, indicated for use in Brazilian winter, with cycle of 110 days from the emergence to maturation. The seeds stayed stored in its respective packages in the Seeds Analysis Laboratory, of the Federal University of Pelotas, until the experiment realization.
The values of water content in seeds were not submitted to statistical analysis. For the data referent to seeds physiologic quality, it was adopted the experimental design completely randomized, with factorial scheme 3 × 3 × 6 (storage environment × package type × storage period) with four replicates, were transformed in arcsin√, in order to homogenize the variance of experimental errors. The presented values in tables are referent to original data.
The experiment was conducted from January to September 2016, where, Factor A-types of packages: paper, plastic and polyethylene (PET); Factor B-storage environments: natural, non-controlled, cold chamber and refrigerator; Factor C-storage periods: 0, 60, 120, 240 and 300 days. It was used four replicates, in subdivided plots, combining the factors type of package and storage environments in the plot and storage period in the subplot.
The packages were polyethylene plastic bags, kraft paper bag and transparent PET bottle. For the cold chamber conditions, the seeds were kept in temperature of 15 ºC (±2 ºC) and relative humidity (RH) between 40 and 50%. The refrigerator condition was temperature of 8 ºC, while for natural environment condition, the seeds were maintained in room with environment temperature, without solar radiation. The values of average temperature and relative air humidity were obtained within the meteorological station of Embrapa Clima Temperado ( Figure  1). plicates of 50 of dry paper. T ions realized 1 (Brasil, 2009 though, in relation to rice (Oryza sativa L.) seeds storage in the same environment, it was observed an increase in humidity degree when in cold chamber (Regalo & Brena, 2006).
The seeds stored in permeable packages (paper) suffered higher influence of atmosphere conditions form the storing local than the ones stored in impermeable packages (PET and plastic). This fact was expected, since this type of package does not offers resistance to vapor exchanges of seed water with the environment, differing from the impermeable, which does not allow exchanges and present higher resistance than the permeable (Table 1). In cambre seeds, the PET package presented higher WVPI (water vapor permeability index), fact that explains the larger oscillation in water content values of seeds within the storage in this kind of package (Bessa et al., 2015).
The relative humidity and temperature conditions during the storing, in which the products will reach its specific hygroscopic equilibrium, will determine the maintaining of its physiologic quality, for a larger or shorter period (Borges et al., 2009). Because of it, it is important to store seeds in packages capable of inhibit gas exchange between the seed and the external environment, causing it to reach hygroscopic equilibrium and avoiding possible seeds tissues detrition due to constant water loss or gain and variation in the respiration ratio.
It is important to highlight that the knowledge of humidity degree of seeds is essential to determine adequate conditions to storage, which depends on the relative humidity that is influenced by environment temperature and package type (Warhm, 1996). According to the variance analysis for the variables first germination counting, germination and seedlings emergence in plant beds, obtained from amaranth seeds cv. BRS Alegria, submitted to different storing periods, conditioned in diverse packages and storing conditions (Table 2). It was possible to observe that there was interaction between the studied factors for the variables germination and field germination. Although, for the variable first germination counting, there was significant interaction for the combination of the factors storage period × packages and storing conditions × packages. However, for being isolated factors, it was instated significance for all studied variables.
Note. * or ns = significant or non-significant at 5% of probability by F test.
For the germination, comparing the package types in each environment and storing period, it was observed that, the storage in natural environment, the percentage of normal seedlings was inferior to those conditioned in PET, independent of the storing period (Table 3). Although, when considering the storage environment, independent of the period and package, it was verified that seeds stored in cold chamber had larger values of viability, except at 180 days, for the plastic and paper packages, being these considered impermeable.
In the comparison of storage environments, when stored in plastic packages, it was verified that, in general, the seeds storage in refrigerator and cold chamber proportionated better maintenance of amaranth seeds germination (Table 3). However, the storing in PET packages, there was larger percentage of normal seedlings in natural environments and cold chamber. When stored in paper packages, it was verified difference in seeds germination only in the evaluations realized at 240 and 300 storing days, where the storage in cold chamber proportionated preservation of the normal seedlings percentage.
Studies executed to evaluate the effects of different storage environments in the germination of amaranth seeds observed that the amaranth seeds can be stored for 16 months in aluminum cans and keep its viability, without harming the germination percentage (Adam et al., 2017). Note. * Means followed by same lowercase letter in line, in each variable, and uppercase in column, in each storing period, do not differ themselves by Tukey test (p ≤ 0.05).
Analyzing the germination behavior within the storage (Figure 2), it was observed that in the natural environment, the storage in plastic package presented quadratic tendency, with fast germination reduction until 215 days of storage, and later increase until the end of storage. In PET storage in natural environment, it was observed low linear reduction of approximately 0.66 germination percentage points for every 60 days of storage. While in the paper package, it was observed cubic behavior tendency for germination, with minimum viability point at 128 days and maximum point of germination at 252 days.
In the refrigerator storage, for all three packages types, it was observed cubic behavior for germination, with reduction of approximately 120, 127 and 106 days, respectively, followed by stabilization and decline of germination at 279, 166 and 180 days, respectively. Stands out the larger germination reduction for the seeds stored in paper, when compared to the reduction observed for other types of packages, presenting 300 days of storage, germination percentage of 6 and 5 percentage points less than the seeds stored in PET and plastic, respectively ( Figure 2). The same behavior was identified in sunflower and pea, which presented reduction in germination when stored in Kraft paper compared to semi-permeable and impermeable packages (Lins et al., 2014;Lisboa et al., 2014).
For the storage in cold chamber, there was reduction of germination with quadratic tendency for seeds stored in plastic packages, with reduction of germination until 295 days. However, for seeds stored in PET and paper packages, it was verified cubic tendency, with initial reduction of germination until the periods of 107 and 132 days, respectively. Later, it was observed stabilization and new reduction of germination, at 257 and 242 days of storing for PET and paper packages, respectively ( Figure 2).
The comparison between storage environments, for seeds kept in plastic packages it was observed difference at 60, 120 and 180 storing days, where the seeds kept in refrigerator has reduction of seedlings emergence, while at 240 and 300 days, the seeds in cold chamber presented lower vigor expression (Table 6). In seeds stored in PET, in general, there was no difference in relation to environment, however, at 240 and 300 days of storage, the seeds kept in natural environment showed lower seedlings emergence. Although, the seeds that were kept in paper packages had, in general, the maintenance of vigor in natural and cold chamber environments. Note. *Means followed by same lowercase letter in line, in each variable, and uppercase in column, in each storing period, do not differ themselves by Tukey test (p ≤ 0.05).
The behavior of seedlings emergence obtained in seeds in natural environment presented tendency of linear reduction of 8.2, 0.76 and 1.1 percentage points for every 60 storing days for plastic, PET and paper packages, respectively, occurring reduction of vigor, even in seeds kept in impermeable packages (Figure 4). The increase in water content in seeds kept in impermeable packages occurs due to the higher respiratory frequency of seeds that proportioned higher waterrelease and increase of relative humidity inside the package, thus, the seeds seek to adjust to the new air relative humidity and, consequently, acquire water content superior to the initial level (Carvalho & Nakagawa, 2012).
For the condition of refrigerator storing, the seeds placed in plastic packages has a cubic tendency, with reduction of emerged seedlings percentage of approximately 124 days, followed by stabilization until the end of