Relationship of photosynthetically active radiation to apparent photosynthetic distributions within soybean canopies

Abstract

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Soil-plant-water relations, growth and nutrient uptake patterns of field-grown soybeans under moisture stress

“…According to a number of authors (Harris, 1973;Dube et al, 1974;Neumann et al, 1974;Turner and Incoll, 1971), the photosynthetic rate was not affected below a critical resistance level but decreased rapidly if the stomatal resistance was greater than the critical resistance. Hatfield (1975) reported that reduced COg uptake occurred through stomatal closure, as evidenced by increased stomatal resistance. Brown and Rosenberg (1970) have shown that for sugarbeets, small decreases in soil-water potential may lead to partial stomatal closure and thereby re duce the photosynthetic rate.…”

“…Hark and Rampage, Hatfield (1975) concluded that the stomatal resistance increased with increasing depth in the canopy.…”

“…;Singh et al, 1968;Luxmoore et al, 1971;Hansen, 1971). Hatfield (1975) used a regression procedure, wherein -In (I/I^) was regressed on the cumulative leaf area index, to determine the extinction coefficient K.…”

“…The regression model used accounted for more than 95?^ of the variation in all cases. Hatfield (1975) In a herbaceous community, the extinction coefficients are generally O.3 to O.5 in stands with upright leaves, and 0.7 to 1.0 in stands with more or less horizontal leaves (Saeki,i960). The difference in extinction coefficients between the two treatments is related to the water status.…”

Corn yield response to moisture stress and foliar fertilizer during grain fill

“…Corn leaf photosynthesis rates were monitored with a carbon-14 carbon dioxide uptake technique developed for field use by Shimshi (1969) and by Incoll and Wright (1969). The method used in our experiments is described by Hatfield (1975) and by Naylor and Teare (1975). The leaf exposure cham ber was modified from that described by Hatfield by attaching it to the handles of a single hole punch for convenience in holding the chamber on 14 the leaf.…”