© 1994 Heron Publishing—Victoria, Canada
Response to light of shade-grown beech seedlings subjected to different watering regimes
Roberto Tognetti (1), Marco Michelozzi (1) and Marco Borghetti (2)
1. Instituto Miglioramento Genetico delle Piante Forestali, CNR, via A. Vannucci 13, 50134-Firenze, Italy / 2. Dipartimento di Produzione Vegetale, Università della Basilicata, via N. Sauro 85, 85100-Potenza, Italy / Received October 18, 1993
Summary
The morphological and physiological responses (net photosynthesis, stomatal conductance, leaf chlorophyll concentration and
leaf orientation) of shade-grown beech seedlings after transfer to a high-light regime were studied in well-watered plants
and in plants subjected to water stress. Immediately after exposure to high irradiance, shade-grown seedlings displayed a
lower photosynthetic rate, a higher leaf chlorophyll concentration and a more horizontal leaf orientation than light-acclimated
plants (control plants). The chlorophyll concentration of shade-grown plants gradually declined throughout the period of exposure
to high irradiance reaching the amount observed in control plants. Rates of photosynthesis of shade-grown plants began to
recover after 8 days of exposure to high irradiance and recovery was nearly complete after 30 days. Leaf orientation of shade-grown
plants also changed rapidly during the first 8 days of exposure to high irradiance and by the end of the experiment, there
were no significant differences between shade-grown and control plants. Water stress caused significant declines in net photosynthesis
and leaf conductance in both shade-grown and control plants. Net photosynthesis did not recover completely in the shade-grown
water-stressed plants during the 30-day exposure to high irradiance. Reversible leaf paraheliotropism and chlorophyll bleaching
were observed in response to soil drying followed by rewatering.
Keywords:
chlorophyll concentration, Fagus sylvatica, high irradiance, leaf orientation, net photosynthesis, stomatal conductance, water stress.
