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ARS Home » Southeast Area » Stoneville, Mississippi » Crop Production Systems Research » Research » Publications at this Location » Publication #327288

Title: Flag leaf photosynthesis and stomatal function of grain sorghum as influenced by changing photosynthetic photon flux densities


Submitted to: International Journal of Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2016
Publication Date: 12/5/2016
Citation: Bruns, H.A. 2016. Flag leaf photosynthesis and stomatal function of grain sorghum as influenced by changing photosynthetic photon flux densities. International Journal of Agronomy. doi:10.1155/2016/1363740.

Interpretive Summary: Grain sorghum yield, like with all crops, is an end product of photosynthesis, where carbon dioxide from the air is combined with water, in the presence of sunlight and produces sugar, part of which goes on to form starch and protein that makeup seed. Information about photosynthesis and related biological reactions that produce yield in grain sorghum is very limited and if better understood, could help explain why sometimes crops fail to achieve expected yield goals. An, ARS Scientist in the Crop Production Systems Research Unit at Stoneville, MS has measured the effects of reducing light intensity to simulate cloud cover on photosynthesis and related biological processes in grain sorghum. Measurements were made at flowering and grain filling, growth stages critical to yield,. Drought and heat stress during grain filling in 2015 greatly reduced photosynthesis at the higher light intensities as compared to the 2014 crop that did not experience these stresses. Nitrogen fertility levels had no effect on photosynthesis or related processes in this experiment. These data indicate the potential for reduced yield due to lower photosynthesis rates brought on by heat and drought stress at grain filling.

Technical Abstract: Data on physiological parameters of A, gs, Em, Ci, and IWUE in grain sorghum (Sorghum bicolor L. Moench) is limited. Flag leaves from three plants of two hybrids, grown using added N fertilizer rates of 0.0, 112, and 224 kg ha-1 near Elizabeth, MS were field sampled for these parameters at growth stages (GS) 6 and 7. A LiCor LI6400XT set at 355 µmol [CO2], a flow rate of 500 µmol s-1, and combined with a 6400-02 LED light source were used to collect data. Light levels were initially set at an indicated 2200 µmol m-2 s-1 PPFD, A allowed to stabilize, data recorded, indicated PPFD level reduced by 200 µmol m-2 s-1 and the process repeated to a PPFD level of 200 µmol m-2 s-1. Data at GS 6 were unaffected by N-fertility, hybrids or years. Data on Ci at GS 6 indicated A declines slight faster with decreasing PPFD than gs. Higher temperatures and less rainfall that occurred in 2015 than 2014 between GS 6 and 7 resulted in reduced A, gs, Em, Ci, and IWEU at GS 7 in 2015 than 2014 at indicated PPFD levels > 800 µmol m-2 s-1.