Response of seedling growth of different seed sizes to cotyledon removal and nitrogen application in Quercus wutaishanica

In this study, the effects of cotyledon removal on the growth of Quercus wutaishanica seedlings and the growth compensation effect of nitrogen application were studied, in order to provide reference for the growth regeneration and seedling breeding of Q. wutaishanica.

Cotyledon removal and nitrogen application (40 g·m^-2·a^-1) were used to determine the shoot height, root height, leaf area per plant and total dry mass, and the root-shoot ratio, specific leaf area, specific shoot length, specific root length, relative growth rate and net assimilation rate were calculated. The differences among the treatments were compared by three-factor analysis of variance.

1) Cotyledon removal significantly reduced shoot height, root length, leaf area per plant, total mass, specific shoot length, relative growth rate and net assimilation rate, and increased the root-to-shoot ratio, specific leaf area and specific root length of large and small seed seedlings. In each treatment, shoot height, leaf area per plant, total mass and specific leaf area of large and small seed seedlings were significantly higher than those of small seed seedlings; 2) Nitrogen fertilization had compensatory effects on the removal of shoot height, root height, leaf area per plant, total mass, specific root length, relative growth rate and net assimilation rate by cotyledon. The leaf area per plant, total mass, specific leaf area, relative growth rate and net assimilation rate of Q. wutaishanica seed seedlings treated with nitrogen cotyledon removal were significantly higher than those treated without nitrogen cotyledon removal.

The effect of cotyledon removal on small seed seedlings of Q. wutaishanica was greater than that of large seed seedlings. Nitrogen application could compensate the growth of large and small seed seedlings of Q. wutaishanica to some extent, but it could not replace the important role of cotyledon in the growth and development of seedlings.