Study On Suitability Of Electrical Conductivity And Radicle Emergence Testing Methods To Determine Seed Vigor Of Three Grass Species

Seed vigor is a comprehensive index reflecting the potential ability of seeds and seed lots to rapidly and neatly emerge and grow into seedlings under a wide range of field conditions.An appropriate method for measuring seed vigor can predict field emergence and seed storage capacity more accurately than standard germination.Different species,due to their different genetic characteristics,usually need to adopt different vigor determination methods.Therefore,it is of great practical significance to develop seed vigor determination methods suitable for different species.Using several seed lots and samples of Hordeum vulgare,Avena sativa and Elymus nutans as materials,this paper investigated the suitability of 2 comparatively potential methods for the determination of seed vigor of 3 important grasses under laboratory and field and other conditions: electrical conductivity and radicle emergence.The main research results are as follows:1.The study on 3 barley cultivars,Ganqing 8,Ganqing 9 and Kunlun 17,showed that the conductivity classification sensitivity of Ganqing 9 and Kunlun 17 was lower than that of standard germination when the conductivity of intact and crosscutting seeds was compared with that of standard germination before and after artificial accelerated aging 96 h.When crosscutting seeds were used to measure the conductivity,aged and unaged samples could be distinguished in all 3 cultivars,indicating that crosscutting could increase the sensitivity of the conductivity method.A total of 29 samples(germination range 76-97%)obtained after gradient aging of the 3 barley cultivars were used for standard germination,laboratory vigor determination and field experiment.The results showed that the radicle emergence method was more accurate in predicting the field emergence rate than the standard germination rate,for example,the correlation coefficients between radicle emergence of 36 hours(RE36)and field emergence rate with 3 cultivars of Ganqing 8,Ganqing 9and Kunlun 17 were 0.850**(P < 0.01,the same below),0.933** and 0.905**,respectively.However,the correlation coefficients between standard germination rate and field emergence rate were 0.757*(P < 0.05),0.549 and 0.093,respectively.In addition,the correlation of evaluation methodology that radicle just breaking through the seed coat was more than radicle lenghth over 2mm.In each single count,counts within 36-48 h was significantly correlated with the field emergence rate in all cultivars(P < 0.01).In order to save experimental time,36 h was recommended as the single count time of seed of the tested cultivars.When the test material was commercial seeds with germination rate bigger than80%,the RE36-RE48 of 8 seed lots of Ganqing 9 was significantly correlated with the field emergence rate(P < 0.05),while the RE36-RE48 of 8 seed lots of Ganqing 8was not significantly correlated with the field emergence rate(P > 0.05).The results showed that RE method was suitable for the determination of the viability of commercial barley seeds of Ganqing 9,but not for Ganqing 8.2.On the basis of previous studies,International reproducible comparative experiments between laboratories were carried out.The results showed that the electrical conductivity had good reproducibility,but the quality classification of the tested seed lot was not accurate enough,which was contrary to the results reported in the past,and the reason needed further study.The results of international inter-laboratory reproducibility studies of radicle emergence method showed that this method had good sensitivity for seed lots quality classification,but poor inter-laboratory reproducibility.In this study,the factors that may affect the repeatability were further systematically studied.The results showed that the difference of water absorption caused by different between-paper germination methods(covering,pleated and rolled)was an important factor affecting the repeatability of single count emergence of radicle.The pleated or rolled paper method is recommended for better control of water content in the paper bed during germination.The results of this study have important guiding significance for RE method standardization.3.Studies on Elymus nutans showed that the quality of seed lot was similar to that of intact and crosscutting seeds.Both intact and crosscutting seeds EC had a high correlation with standard germination rate(r=-718;r =-0.761)and was significantly negatively correlated with single count of RE of 76h(r=-0.982;r = 0.990).The single count of radicle emergence was more sensitive to the quality classification of Elymus nutans seed lot than the standard germination rate.In general,the RE method is suitable for the determination of seed vigor of tested grasses,and is worthy of model applied in a wider range of field conditions.There is still great uncertainty in the determination of vigor of grass seeds by electrical conductivity,and the reasons need to be further studied.