EVALUATING THE VIABILITY OF AGRIOPHYLLUM SQUARROSUM SEEDS Y.J. ZENG*, X.N. QI, Y.Z. Li,Y.Q. WANG AND Y.R. WANG. INTRODUCTION Agriophyllum squarrosum grows exclusively in active dunes and is the first species to grow effectively on dunes (Figure 1). Many of A. squarrosum seed samples failed to germinate under the germination test conditions prescribed in the rules for Quality Grading and Testing for Main Sandy Forage Seed. The embryos were very flaccid and their colours varied after staining according to the rules for Grading and Testing of Agriophyllum squarrosum (L.) Moq. Seed). Given the uncertain viability results or ‘poor germination percentage’, seed transactions were suspended. To rapidly and accurately estimate the viability of the seed, we propose two methods of seed pre-preparation, namely, cutting or piercing, prior to tetrazolium solution staining. To determines the tetrazolium testing procedure to verify the viability of A. squarrosum seeds.
Figure 1. Agriophyllum squarrosum from the dunes of the northeastern Tengger Desert in Inner Mongolia, China.
MATERIAL AND METHODS Seven samples (table 1) of A. squarrosum seeds were obtained from Minqin County Gansu province, China. These seeds were prepared for tetrazolium testing through three approaches, namely, keeping the seed intact, piercing the centre of the seed and cutting through the basal half of the seed longitudinally. Viability was also assessed through a germination test.
Figure 2. Patterns of Agriophyllum squarrosum embryos of sample 1 stained with 1% tetrazolium solution at 30 °C in the dark. Intact seeds at 12 hours (a), 22 hours (b) and 30 hours (c); pierced seeds at 10 hours (d), 20 hours (e) and 28 hours (f); and cut seeds at 10 hours (g), 20 hours (h) and 28 hours (i).
Table 1. Sample number, production year, seed age, thousandseed weight and percentages of viable seed and germination of Agriophyllum squarrosum seeds tested.
Table 2. Proportions of viable and non-viable Agriophyllum squarrosum seeds evaluated based on staining patterns and structural integrity.
Sample
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 7
Viable Germinati Productio Seed age Thousand seed (%) on (%) n year (month) seed weight (g) 2013 1 1.30 b 99.8 a 50.0 b 2012 13 0.88 d 99.3 a 54.0 b 2012 13 1.65 a 99.3 98.8 2012 13 0.87 d 97.8 a 89.8 b 2011 25 1.13 c 98.5 93.3 2008 61 0.76 e 98.8 96.5
Sample Sample 1
Preparati on
Prior to piercing or cutting, the seed should be pre-moistened in 20 °C water for at least 24 hours. Intact seeds were unsuitable for tetrazolium testing because most of them remained unstained after 30 hours in the tetrazolium solution (Figure 2c). Piercing or cutting the seeds to expose the embryo required a similar optimum staining time (10 hours) and resulted in a similar staining effect and viability percentage (figure 2d, g). Nonetheless, piercing was recommended as the optimum tissue exposure method over cutting because the latter is time-consuming and may cause damage to the embryo. All seven seed samples exhibited high viability percentages (97.8-99.8%). Four samples displayed similarly high germination percentages (93.3-98.8%) (table 1), whereas the percentages of the other three seed samples were significantly different (89.8-50.0%) than the viabilities recorded (P < 0.05, N = 4).
2
99.7 a
0
0.0 c
0.3 c
Cut
96.9 a
2.3
0.0 c
0.8 c
1.3 b
0
87.9 a
10.8 b
Pierced
99.2 a
0
0.3 c
0.5 c
Cut
97.7 a
1.5
0.3 c
0.5c
3.8 b
0
63.7 b
32.5 a
Intact
RESULTS AND CONCLUSIONS
1
Pierced Intact
Sample 2
Non-viable seed (%) 3 4
Viable seed (%)
PROCEDURE - Pre-moistening seeds at 20 ºC in water for a minimum time of 24 hours followed by piercing in the centre. - Staining at 30 ºC in the dark in a 1.0% tetrazolium solution; optimum staining time is approximately 10 hours. - When preparing the stained embryos for evaluation, the observed tissue is the external embryo surface. The maximum area of unstained, flaccid or necrotic tissues permitted for viable seed is one third of the radical tip and/or one third of the distal area of the cotyledons. ACKNOWLEDGEMENTS: PCSIRT (IRT13019), NSFC (31272496). * State Key Laboratory of Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China, (E-mail:
[email protected]) .
