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Regulation of the growth, development, and quality of plants by the control of light quality has attracted extensive attention worldwide. The aim of this study was to examine the effects of continuous LED spectrum for indoor plant pre-cultivation and to investigate the morphological and physiological responses of a common broadleaved tree species in Mediterranean environment, Quercus ithaburensis var. macrolepis at seedling developmental stage. Thus, the seedlings were pre-cultivated for 28 days, under five different LED light qualities: (1) Fluorescent (FL) as control light (2) L20AP67 (high in green and moderate in far-red), (3) AP673L (high in green and red), (4) G2 (highest in red and far-red), AP67 (high in blue, red, and far-red), and (5) NS1 (highest in blue and green and lowest in far-red) LEDs. Further examination was held at the nursery for 1 year, on several seedling quality traits. Indeed, AP67 and AP673L triggered higher leaf formation, while L20AP67 positively affected seedling shoot development. NS1 and AP67 LED pre-cultivated seedlings showed significantly higher root fibrosity than those of FL light. Furthermore, NS1 and AP673L LEDs induced fourfold increase on seedling root dry weight than FL light. Hence, evaluating the seedling nursery performance attributes, most of those photomorphogenetic responses previously obtained were still detectable. Even more so, LED pre-cultivated seedlings showed higher survival and faster growth indicating better adaptation even under natural light conditions, a fact further reinforced by the significantly higher Dickson’s quality index acquired. In conclusion, the goal of each nursery management program is the production of high quality seedlings with those desirable traits, which in turn satisfy the specific needs for a particular reforestation site. Thus, the enhanced oak seedling quality traits formed under continuous LEDs spectrum especially of NS1 and AP673L pre-cultivation may potentially fulfill this goal.

No abstract

Light intensity required by forest species has been widely studied, leading to their classification in heliophilous, sciaphilous and intermediate species. Conversely, few studies are available on light quality requirements. Artificial lights for plant growth have been designed mainly for agricultural crops that are all heliophilous, with high percentages of blue and red wavelengths in order to increase the photosynthetic activity. These light sources may be considered adaptable to heliophilous forest species; in order to test this hypothesis, a presumed heliophilous species, Platanus orientalis, was cultivated under different LED and fluorescent light sources, commercially available, in a controlled growth chamber. Some seedlings showed a progressive yellowing or reddening of leaves, leading to the hypothesis of a light stress. Therefore, the real light conditions in which natural regeneration occurs were analysed. The Natural Reserve of Pantalica (Sicily), was chosen as study area. Light spectra were collected along Anapo river, in July, from 10 a.m. to 2 p.m., in correspondence of different points with and without natural regeneration. Seedlings resulted to grow in slight shadow, frequently interrupted by short sunflecks. The spectra associated to shadow and sunflecks resulted to be different, both in terms of quality and quantity. Therefore, it seems that Platanus orientalis is not properly heliophilous, as reported in literature; this fact may explain why, as some sciaphilous species, it lacks of a complete xantophyll cycle, showing only leaf hairs as a protection against light excess. The results of this research show that the analysis of light requirements for each species is essential to define the best light conditions, in terms of quality and quantity, for artificial propagation.