Abstract
Light is necessary for plant growth, but excess light inhibits photosynthesis and furthermore leads to the breakage of pigments.
Quercus crispula is a dominant species in boreal forests. It grows under the crown until the formation of gap and then acclimates to low light conditions. Once a gap is formed, it grows up to the crown. Therefore, it experiences a large difference in light intensity during growth. It is suggested that the water-water cycle and xanthopyll cycle play important roles in the protective mechanisms against a rapid increase in light intensity.
However it is not clear whether such mechanisms work also in Q. crispula. To clarify whether these mechanisms work in Q. crispula, we grew the seedling under 4 conditions (combinations of high-low light intensities and high-low temperatures). Then we measured photosynthetic rate, the amount of excess energy, carotenoid contents and the activities of APX from leaf flush to senescence.
