Search Results

You are looking at 1 - 2 of 2 items for

  • Author or Editor: Xenia Y. Wolff x
Clear All Modify Search
Free access

Xenia Y. Wolff and Robert R. Coltman

`Waimanalo Long' eggplant (Solanum melongena L.), `Kahala' soybean [Glycine max (L.) Merrill], `Jumbo Virginia' peanut (Arachis hypogea L.), `Waimanalo Red' sweet potato [Ipomea batatas (L.) Lam.], and `Green Mignonette' semihead lettuce (Lactuca sativa L.) were field-grown in two seasons at Waimanalo, Oahu, Hawaii, in the open sun and with four artificially produced levels of shade (30%, 47%, 63%, and 73%). Yields and vegetative growth of eggplant, soybean, peanut, and sweet potato decreased linearly with increasing shade levels. Compared to unshaded controls, yields of semihead lettuce increased significantly under 30% shade in Fall 1986. During Spring 1987, lettuce yields were reduced only slightly from unshaded levels by increasing shade up to 47%. Leaf areas of index leaves of eggplant, soybean, and lettuce were similar to unshaded controls as shade intensity increased, while leaf dry weight decreased under shade. By comparison, both leaf area and leaf dry weight of peanut index leaves decreased as shade increased. Leaf area and leaf dry weight of sweet potato did not respond to shading. The results indicate that, of the five crops studied, only lettuce can be grown successfully under lightly shaded conditions and still receive enough radiant energy for maximum photosynthesis and yields.

Free access

Xenia Y. Wolff and Robert R. Coltman

`Green Mignonette', `Salinas', `Parris Island Cos', and `Amaral 400' lettuce (Lactuca sativa L.); `WR-55 Days' Chinese cabbage (Brassica rapa L. Pekinensis Group); Waianae Strain' green mustard cabbage [Brassica juncea (L.) Czerniak]; `Tastie Hybrid' head cabbage (Brassica oleracea L. Capitata Group); and an unnamed local selection of green bunching onions (Allium fistulosum L.) were field-grown during Fall 1987 and Spring 1988 at Waimanalo, Oahu, Hawaii, in full-sun and with four artificially produced levels of shade (30%, 47%, 63%, and 73%). Yields of cos lettuce, green mustard cabbage, and green bunching onions were irresponsive to shade or negatively affected by shade in both seasons. Yield responses of the other crops to shade varied seasonally. Optimum shading of 30% to 47% increased `Green Mignonette', `Salinas', and `Amaral 400' lettuce yields by 36% and head cabbage and Chinese cabbage yields by 23% and 21%, respectively, compared to full-sun plots in one or both seasons. Leaf areas similar to unshaded controls were maintained as shade intensity increased, while leaf dry weight decreased in all crops except `Salinas' and `Parris Island Cos' lettuce. Maximum rates of net photosynthesis (Pn) were attained at 1500 umol·s-1·m-2, which was about two-thirds of full sunlight.