Abstract
Early vigor is important for crop establishment in rice. This study was conducted to determine the seed and seedling traits in relation to early vigor in rice. Laboratory tests and pot experiments were carried out in 2013 and 2014. Morphological and physiological traits of seeds and seedlings were compared between two contrasting rice cultivars, Yuxiangyouzhan with superior early vigor and Huanghuazhan with general early vigor. For seed traits, Yuxiangyouzhan had lower seed hull weight but higher seed amylose content, seed amylase activity, and plumule–radicle ratio than Huanghuazhan, and consequently, Yuxiangyouzhan had about 10% higher germination percentage and velocity and 37% longer plumule than Huanghuazhan. For seedling traits, leaf area, specific leaf weight, leaf chlorophyll and soluble protein contents, leaf net photosynthetic rate, and shoot–root ratio were higher in Yuxiangyouzhan than in Huanghuazhan, and as a result, seedling shoot biomass was 23–32% higher in Yuxiangyouzhan than in Huanghuazhan. These results indicate that Yuxiangyouzhan has both superior seed and seedling vigor. The former is attributed to the low mechanical strength of seed hull, high conversion efficiency of seed reserve, and high mobilization of seed reserve to plumule, while the latter is due to large leaf area, high leaf photosynthetic capacity, and high partitioning of dry matter to shoot. This study enriches the physiological understanding of superior early vigor in rice.
Highlights
Rice is the staple food for more than 65% of the population in China
Morphological and physiological traits of seeds and seedlings were compared between two contrasting rice cultivars, Yuxiangyouzhan with superior early vigor and Huanghuazhan with general early vigor
There were no significant differences between Yuxiangyouzhan and Huanghuazhan in seed size and weight and embryo weight, while seed hull weight was significantly lower in Yuxiangyouzhan than in Huanghuazhan
Summary
Rice is the staple food for more than 65% of the population in China. Over the past few years, the expansion of cities has led to a labor shortage for agricultural production (Peng et al, 2008), and the simple and labor-saving method of direct seeding has become very popular in rice production (Huang et al, 2011; Liu et al, 2015). Seed carbohydrate reserve is important for seed vigor in rice since carbohydrates for germination and heterotrophic growth are provided by breakdown of the starch stored in the endosperm (Cui et al, 2002). This has been indirectly supported by a number of investigations showing a close relationship between early vigor and seed size or weight in rice (Lu et al, 2007; Namuco et al, 2009; Wang, Wang et al, 2010), but direct evidence is lacking. Amylose is composed mainly of linear chains of α-1, 4-linked glucose residues and can be
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