01391nas a2200133   4500008004100000245009700041210006900138300001300207490000800220520095500228100001401183700002001197856004001217       1998                        eng d00aResponses to short-term shade in soybean leaves: Effects of leaf position and drought stress0 aResponses to shortterm shade in soybean leaves Effects of leaf p  a805 -8110 v1593 aThis study examined how leaf position in the canopy affected photosynthetic and stomatal responses to short-term, minutes-long shade periods during a drought cycle in soybean (Glycine max [L.] Merr.). All soybean leaves had similar basic responses to short-term shade, including rapidly decreased photosynthetic rates (Aco2 ), slower decreases in stomatal conductance (g,), and delayed stomatal reopening and photosynthetic recovery after leaves were reilluminated. Drought stress lowered overall Aco2 and restricted photosynthetic and stomatal responses to short-term shade with the negative effects of drought being stronger in lower than in upper leaves. Some of the negative effects of drought persisted after drought was relieved, causing reduced overall water use efficiency, especially in lower leaves. These results indicate that leaf position effects on stomatal responses to short-term shade events become important during and after stress.1 aFay, P.A.1 aKnapp, Alan, K.  uhttp://www.jstor.org/stable/2475151