the method proposed is based on detection of the activity of the alpha - amylase enzyme released into the culture medium , as a way of determining the viability of any plant tissue . in general terms , the method is based on the ability of the alpha - amylase enzyme for degrading the starch present in the culture medium of the detection device where the plant sample is grown , the degradation is evidenced by the lack of color on the surface of the culture medium of the device , upon being revealed with an iodine - based solution . the alpha - amylase enzyme is mainly present in plant tissues , whereby the method has a level of selection toward the growth of other organisms , without prejudice to the foregoing . preferably , the method is developed under conventional aseptic conditions of the state of the art . the alpha - amylase enzyme is present in all plant tissues and cells , and although it exhibits a different degree of presence and activity in the different tissues and stages of development of a plant , they are perfectly detectable through the proposed method . the method disclosed allows to determine viability in plant samples from different species of gymnosperm or angiosperm , monocotyledonous or dicotyledonous plants , from plants grown in vivo or cultured in vitro . on the other side , the present method allows to determine viability at different stages of development of the plant , for example , and not limited to organogenesis , callogenesis , somatic embryogenesis , differentiated tissues and sex tissues . the method for determining viability allows to determine viability in plant tissues from different parts of the plant , not limited to leaves , stems , petioles , calluses , embryos , protocorms , rhizomes or roots , in addition to polen and seeds . the method for determining viability as designed may be applied to any plant culture process which requires a viability detection step either with commercial , scientific research or other purposes , for example , and not limited to , micropropagation technology , viability in polen grains , viability of in vitro and ex vitro tissues submitted to biotic and abiotic stress , viability of tissues from genetically engineered plants , viability of ovaries , detection of the viability of any plant tissue and culturing in bioreactors . the culture medium is chosen from the state of the art according to the nutritional requirements typical of the plant tissue to be analyzed . the culture medium may be supplemented with compounds normally used in processes such as : culturing plant tissues ; selecting transformed tissues ; avoiding contamination of the medium with other prokaryotic or eukaryotic organisms ; stimulating the morphogenic response of the tissues ; ensuring the development and growth of the cells or tissues in the physiologic state in which the present viability detection method is developed , among others . the compounds with which the culture medium may be supplemented comprise , for example : inorganic salts , organic salts , minerals , vitamins , aminoacids , natural or synthetic growth regulators , agar or any other polymer used to solidify culture media , bactericides , fungicides ; organic acids and inorganic acids and water . the culture medium is additionally supplemented with starch . preferably , the starch concentration of the culture medium is between 0 . 5 and 5 . 0 gl − 1 , preferably between 1 . 0 and 3 . 0 gl − 1 , more preferably between 1 . 0 and 2 . 0 gl − 1 . the revealing composition is based on iodine with a 10 % iodine solution , the revealing composition may further contain preservatives , such as organic acids , antibiotics and fungicides . the device is manufactured under regular sterility and asepsis conditions described in the state of the art . the plant sample is treated considering the normal aseptic conditions described in the state of the art . in the method for determining viability , the plant samples are placed on the surface of the culture medium of the device and are incubated for a period of time and in temperature conditions suitable for each plant species . preferably , the culturing of plant tissues is carried out in dark conditions since a greater starch uptake by the plant tissue is obtained . in step c ) the tissue sample is removed from the culture medium . the analyzed plant sample may be subsequently subcultured in culture medium without starch or used according to the purposes deemed convenient by the user . in step d ) for revealing the viability detection device , an iodine solution is poured onto the surface of the culture medium which is incubated for a period of time at room temperature . preferably , this incubation lasts between 3 and 5 minutes and is conducted between 20 and 25 ° c . subsequently , the iodine solution is removed from the surface and , as a positive viability result , a colorless halo is observed in the location where the plant sample was grown . this halo reflects the degradation of the starch present in the culture medium . degradation of the starch by the enzymes of the plant is evidenced visually , thus detecting the viability of the assessed sample . if the tissue is alive , a colorless halo is observed underneath the place where the tissue was located . the halo may be of a variable size , depending on the type of tissue and the plant species , however , clear differences are observed between the color of the culture medium and the halo formed in the zone where the explant was cultured , when the tissue is viable . if the tissue is dead , the surface underneath the evaluated explant is stained with blue similar to the rest of the culture medium . to define the starch composition of the test culture medium to be used in the following experiments , tests were conducted with basic culture medium supplemented with different starch concentrations . in this experiment ( fig1 ), nodal segments of tobacco ( nicotiana tabacum ) were used as a model . the culture medium was prepared with ms basal medium ( murashige and skoog , 1962 ) and agar - agar ( 7 gl − 1 ), supplemented with sucrose ( 30 gl − 1 ) and different amounts of starch ( 0 . 5 gl − 1 , 1 . 0 gl − 1 , 1 . 5 gl − 1 , 2 . 0 gl − 1 ). the ph of the culture medium was adjusted to 5 . 6 - 5 . 7 , before sterilizing . sterilization of the culture medium was performed by pressurized steam in an autoclave at a temperature of 121 ° c ., a pressure of 1 kgcm − 2 and for 30 minutes . once sterile , the culture media were dispensed into viability detection devices such as petri plates in aseptic conditions . the explants were taken from aseptic nodal segments of tobacco grown in vitro . the explants were prepared in segments of 0 . 5 cm in length and 0 . 5 cm in length . once prepared , the explants were placed in the viability detection devices , trying to keep sufficient distance therebetween to avoid interferences in the signs of viability , preferably 5 explants per device . the explants were cultured for 1 , 2 , 3 and 5 days , at 25 ° c . and in dark conditions . after this incubation period , the explants were removed from the plates and the latter were revealed with an iodine solution as indicated in the following paragraph . revealing of the plates was performed using an iodine solution diluted to 10 %. the iodine solution diluted to 10 % was prepared in two steps : firstly , a colorless solution of potassium iodide ( ki ) at 300 gl − 1 was prepared . subsequently , the ki solution was used to prepare the iodinated solution by adding 233 . 1 ml of ki solution and 56 g of iodine crystals to 500 ml of distilled water . the solution was stirred for 1 hour or until the crystals were completely dissolved and the solution was homogenized , and was left to stand for 24 hours . finally , the volume of the solution was adjusted by adding 3 . 5 liters of distilled water . to visualize the signs of viability in the detection plates , a film of iodine solution diluted to 10 % was applied for 3 minutes on the surface of the plates until staining was observed in the culture medium . subsequently , the iodine solution was removed from the surface of the plates by runoff . fig1 shows the results of the standardization of the culture medium in viability detection experiments on nodal segments of tobacco , in plates b , c and d , a colorless halo is observed on the surface where the implants were cultured , demonstrating the viability of the grown tissues . it was determined to use 1 . 5 gl − 1 of starch in the culture medium as the preferred concentration for cell viability detection in this experimental model . viability detection in different explants from strawberry ( fragaria chiloensis ), tobacco ( nicotiana tabacum ), blueberries ( vaccinum corymbosun ) and andean papaya ( carica vasconcellea ) viability tests were conducted on explants obtained from different plant species and different tissues thereof , using our viability detection device . the experimental steps for detecting the viability of the different tissues are described below : ms basal medium ( murashige and skoog , 1962 ) was used , supplemented with 1 . 5 gl − 1 of starch , 30 gl − 1 of sucrose , 7 gl − 1 of agar - agar and growth regulators according to the type of explant and the species , as indicated in table 1 . this working concentration was chosen according to the type of explant , the plant species and the morphogenic process in which the viability detection is performed . the basal salts and the vitamins of the ms medium were added according to the concentrations suggested for the preparation of this culture medium , without any modification ( murashige and skoog , 1962 ). the ph of the culture medium was adjusted to 5 . 6 - 5 . 7 , before sterilizing . sterilization of the culture medium was performed by pressurized steam in an autoclave at a temperature of 121 ° c ., a pressure of 1 kgcm − 2 and for 30 minutes . once sterile , the culture media were dispensed into petri plates in aseptic conditions . the plates may be sealed and kept in the dark and at room temperature for up to 30 days before being used . all explants were taken from plants grown under in vitro conditions . the explants were prepared in segments of 0 . 5 cm in length and 0 . 5 cm in length in the case of the leaves ; 0 . 5 cm in diameter for the calluses ; 0 . 5 cm in length for the nodal segments and petioles . c ) culturing of the explants in the culture plates and viability assay . once prepared , the explants were placed in the viability detection plate , trying to keep sufficient distance therebetween to avoid interferences in the signs of viability . in this case , not more than 6 explants were placed in plates of 10 cm in diameter , without prejudice to other densities in the species and tissues that might permit them . all the explants were placed on the culture medium as if they were to be manipulated for generating morphogenic responses according to the indications of the protocols for each species . the explants were cultured in the viability detection plates from 24 hours to 5 days and were cultured at 25 ° c . and in dark conditions . the explants were removed from the viability detection medium for the subsequent revealing of the plates . the explants were subcultured in a culture medium recommended for each species to induce the desired morphogenic response . in this case , the basal culture medium described in table 1 was used , but without the addition of starch . fig6 shows that the culturing period in the viability detection medium did not affect the morphogenic response . revealing of the viability detection plates was performed using an iodine solution diluted to 10 %. this solution was prepared according to the protocol for the preparation of the iodine solution described in example 1 . to visualize the signs of viability in the detection plates , a film of iodine solution diluted to 10 % was applied for 3 minutes on the surface of the plates until staining was observed in the culture medium . subsequently , the iodine solution was removed from the surface of the plates by runoff . as a way of control , viability tests were carried out with samples of living and dead tissues . to this end , rhizomes of the terrestrial orchid chloraea crispa cultured in vitro were used . the dead tissue samples were obtained by sterilizing them in an autoclave at 121 ° c . and 1 kgcm − 2 for 40 minutes . fig2 shows the results of the experiment , demonstrating that the detection system allows to clearly determine the viability of the tissue under study , since a colorless halo can be clearly observed on the surface of the plate where the living tissues were cultured ( fig2 a ), due to the degradation of the starch in this sector of the plate . the halos are not observed in the plates with dead tissues ( fig2 b ). fig3 , 4 and 5 show the results of the viability tests performed for some of the types of tissues described in table 1 . in these photographs , it can be confirmed that the system proposed allows to detect the activity of living tissues of different origins , both at the level of species and of tissue type , independent of the basal culture medium used . it should be mentioned that the tissues used in these tests are those commonly used in the in vitro multiplication protocols of most plant species . to determine the possible effect of starch on the normal growth and morphogenic response of the tissues submitted to the viability detection test , nodal segments of tobacco were cultured for 15 days in basal propagation medium ( ms medium ) supplemented with different carbon sources . the culture media were prepared according to the protocol described in the preceding examples . three different culture media were prepared , which were : without carbon source ( fig6 a ), culture medium supplemented with sucrose at 30 gl − 1 as an energy source , and starch at 1 . 5 gl − 1 ( fig6 b ) and culture medium supplemented only with starch at 1 . 5 gl − 1 ( fig6 c ). fig6 shows the effect of the different types of culture media on nodal segments of tobacco . in the photographs of fig6 a and 6c , scarce growth of the plants is observed , showing that starch does not replace the carbon source for these cultures . on the other side , in fig6 b it can be appreciated that starch did not affect the growth of the cultured plant , and the growth and morphogenic response produced were normal for the plant .
a method for determining the viability of a plant sample includes providing a viability detection device containing a solid or semisolid culture medium suitable for the nutritional requirements of a plant sample , wherein the culture medium has a starch supplement ; growing the plant tissue in the viability detection device from the previous step ; removing the plant tissue sample from the viability detection device ; and revealing the viability detection device .