Author
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Baker, Jeffrey |
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Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/20/2006 Publication Date: 3/12/2007 Citation: Baker, J.T. 2007. Cotton seedling injury and recovery from wind blown sand abrasion: I. Duration of exposure. Agronomy Journal. 99(2):556-561. Interpretive Summary: Millions of acres of crops are exposed to wind blown sand abrasion injury each year and in many instances the damage is thought to be sufficiently severe to require replanting. The goal of this study was to determine the effects of wind blown sand abrasion duration on cotton seedlings. Three varieties of cotton seedlings were exposed to wind blow sand in a wind tunnel for periods of time ranging from 0 to 40 minutes. Increasing duration of exposure increased the amount of damage the plants received. Growth rates were measured during two time intervals following the sand abrasion treatments. The first time interval of two weeks following the sand abrasion treatment revealed a decrease in growth rate with increasing sand abrasion duration caused by the injured plants shedding damaged leaves. In the second time interval of two weeks after the first time interval we measured growth rates of the recovering plants. During this recovery phase relative growth rates were actually increased with increasing sand abrasion duration treatment. This faster growth of previously damaged plants in the second or recovery phase was attributed to either a reallocation of biomass from the roots or a greater efficiency of photosynthesis. Technical Abstract: Millions of acres of crops are exposed to wind blown sand abrasion injury each year and in many instances the damage is thought to be sufficiently severe to require replanting. The goal of this study was to determine the effects of wind blown sand abrasion duration on cotton seedlings. Seedlings of three cotton (Gossypium hirsutum L.) cultivars were exposed to wind velocities of 13.4 m s-1 with sand abrasive flux density of 0.42 g /cm width per second for six treatment durations ranging from 0 to 40 minutes. Plants were destructively sampled at the time of the sand abrasion treatment and also at approximately two and four weeks after exposure. These three sampling dates provided two time intervals for assessing the amount of plant damage and re-growth using classical growth analysis. With increasing sand abrasion treatment time, leaf area and leaf, stem and total biomass were all significantly reduced while final number of mainstem nodes were increased (P ' 0.05). Cultivar differences in leaf mass were significant only at the second destructive sampling date (P ' 0.05). For the first harvest interval, between the first and second destructive sampling, shoot relative growth rate (RGR) and net assimilation rate (NAR) decreased with increasing sand abrasion treatment time presumably due to the loss of damaged leaf biomass and reductions in light interception. Re-growth during the second harvest interval revealed the opposite pattern with RGR and NAR both increasing with increasing sand abrasion treatment time. During the second harvest interval, the increase in shoot RGR and NAR with increasing prior sand abrasion damage may be the result of remobilization of stored assimilate and/or increased photosynthesis per unit leaf area for newly formed leaves caused by either reduced self shading or possibly increased sink demand for assimilate. Leaf area ratio (LAR) was not affected by treatment time in either harvest interval. Thus, in both harvest intervals variation in RGR depended mainly on NAR rather than LAR. |
