In an effort to determine the optimal light level for growing pawpaw [Asimina triloba (L.) Dunal] seedlings outside, seedlings were germinated in a greenhouse until the two- to three-leaf stage, at which time they were placed outside and shade treatments were imposed that reduced incident light intensity by 30%, 55%, 80%, and 95%. Control seedlings were left unshaded outside. A randomized block design was used, with 20 replicate seedlings in each experimental treatment per block. Plants were destructively harvested 11 weeks after the start of the experiment. After 11 weeks, the height and number of leaves per seedling were about 35% higher with light to moderate shading (30%, 55%, and 80%) than in control (unshaded) seedlings. Shoot and leaf dry weights of seedlings grown in 30%, 55%, and 80% shade were almost 2-fold greater than control plants. Root dry weight of seedlings in 30% and 55% shade was 2-fold higher than in control plants. Total plant biomass was greatest in the 30%, 55%, and 80% shade treatments, about 2-fold higher than control plants. Total leaf area per seedling increased significantly with up to 80% shading. Seedlings growing under 95% shading had fewer and smaller leaves and reduced biomass production compared to control plants. There was a trend for shaded plants to display a higher leaf chlorophyll content than control plants. Overall, the best seedling growth was achieved in the 30% and 55% shade treatments outdoors.
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