JIA-2019-11

2529 ZHOU Tian-mei et al. Journal of Integrative Agriculture 2019, 18(11): 2521–2533 be of great importance to vegetable production. Seedlings with distinct qualities are generally observed in greenhouses with suboptimal environmental conditions. Improving seedling quality through manipulating environmental conditions of nurseries is an efficient way to enhance crop field performance. However, the environment of modern nurseries is complex and dynamic. In addition, growth conditions are generally crop species-dependent (Brisson et al . 2003; Keulen 2012), so optimal environmental conditions for one crop species may not be suitable for other species. Therefore, it is challenging to effectively improve seedling quality through optimizing nursery environmental conditions without understanding the relationship between seedling growth and multiple environmental conditions. However, few studies have focused on the prediction of nursery stock quality using composite environmental factors like temperature and illumination in tomato and cabbage. And many studies have shown that reliable composite indexes (such as G value and healthy indexes), instead of single indexes accurately reflect stock quality and correspond to eld success (Lentz 1998; Marcelis et al . 1998; Zhang et al . 2004; Bai et al . 2014). Therefore, our objective was to develop a simulation model of seedling quality based on both light and temperature. This model can provide a theoretical basis for standard seedling management and the cultivation of higher-quality seedlings. In this study, we established a simulation model of seedling healthy index [(Stem diameter/Plant height)×Dry mass of plant] based on production of TE and PAR (TEP) in tomato and cabbage, and this model exhibited good fitting degree and high predictability. To simplify the procedure and develop a practical model, light and temperature were chosen from the main impact factors influencing seedling growth, which include light, temperature, fertilizer, water, and hormones (Li et al . 2008; Abbas et al . 2013; De Ron et al . 2016). For seedling production in nurseries, fertilizer and water are relatively easy to be optimized for seedling growth (Li et al . 2008). Hormones could introduce complications because they are regulated by many factors (Abbas et al . 2013). Light and temperature are frequently used with composite indexes like fruit growth, leaf area, photosynthetic rate, dry matter production, etc. to develop plant growth simulation model (Li et al . 2005, 2008; Ni et al . 2009; Xu et al . 2010). Temperature and light in greenhouse can be artificially regulated, so they are not necessarily synchronized (Li et al . 2004, 2013). Therefore, using a comprehensive indicator based on both light and temperature is necessary for developing robust simulation models. Field performance can be predicted by assessing nursery stock quality (Korkmaz and Dufault 2004). However, it is extraordinarily difficult to accurately evaluate seedling quality 0 15 30 45 60 0 0.003 0.006 0.009 0.012 TEP (MJ m –2 ) A B C D 0 15 30 45 60 TEP (MJ m –2 ) 0 15 30 45 60 TEP (MJ m –2 ) 0 15 30 45 60 TEP (MJ m –2 ) 0 0.003 0.006 0.009 0.012 HI1 0 0.03 0.06 0.09 0.12 HI2 0 0.015 0.030 0.045 0.060 HI3 G value (g d –1 ) Simulated values Measured values of Bochun Measured values of Sugan 27 Fig. 6 Validation of G value and healthy index models in cabbage seedlings. TEP, thermal effectiveness and photosynthetically active radiation. G value refers to the ratio of whole plant dry mass to days of seedling (eq. (5)); HI1, HI2 and HI3 are different seedling healthy indexes (eqs. (6)–(8)).