Ameliorative effects of potassium on drought-induced decreases in fiber length of cotton(Gossypium hirsutum L.) are associated with osmolyte dynamics during fiber development

Fiber length of cotton(Gossypium hirsutum L.)decreases under drought stress,potassium(K)could diminish the decreased caused by drought,but the mechanism associated with this alleviation effect is not clear.We evaluated the effect of K on fiber elongation using two cotton cultivars,Simian 3 and Siza 3,grown in well-watered and drought-stressed conditions.Potassium fertilizer(K2O)was applied 0,150,or 300 kg ha?1 in each growing condition.Drought stress reduced the final fiber length due to a decline in the maximum rate of rapid elongation(Vmax,mmday?1).The application of K alleviated the droughtinduced fiber length reduction by increasing Vmax.At 10 and 15 days post-anthesis(DPA),drought significantly reduced osmotic potential(OP)and increased K+and malate contents at all K rates,relative to well-watered conditions,which was associated with increased activities of phosphoenolpyruvate carboxylase(PEPC),V-ATPase,PPase,and PM H+-ATPase in cotton fiber.However,the relative contribution of K+and malate to OP declined under drought in comparison with well-watered condition.Compared with control without K,K application decreased OP and increased the accumulation of osmolytes(K+,malate and soluble sugar)as well as the activities of related enzymes in fiber irrespective of water treatments.Moreover,K application increased osmotic adjustment during drought,and improved the contribution of K+and malate to OP,especially under drought stress.This study showed that drought decreased fiber length by reducing Vmax,and K application ameliorates the decline in fiber elongation due to drought by enhancing osmolytes accumulation and their contribution to OP in fiber cells.

High Temperature and the Ethylene Antagonist 1-Methylcyclopropene Alter Ethylene Evolution Patterns,Antioxidant Responses,and Boll Growth in Gossypium hirsutum

The cotton (Gossypium hirsutum L.) crop experiences high temperatures during flowering and boll development, but information regarding the impact of ethylene inhibition and high temperature on early boll development is limited. The objective of this study was to determine the effects of high temperature and the anti-ethylene compound 1-methylcy-cloprone (1-MCP) on G. hirsutum boll development. Treatments consisted of temperature regime (38/20?C and 30/ 20?C), 1-MCP treatment, and days past anthesis (DPA). High temperature decreased ethylene synthesis by 61% at 2 DPA, and 1-MCP caused a 40% decrease in ethylene production at 1 DPA. Glutathione reductase activity increased under high temperature, whereas superoxide dismutase activity (SOD) and membrane peroxidation (malondialdehyde content) remained unchanged. 1-MCP treatment did not affect GR activity in developing bolls. High temperature and 1-MCP treatment increased the weight of cotton bolls collected 8 DPA with an increase of 0.7 and 1 g, respectively. We propose that increased GR activity in bolls exposed to high temperature may mitigate oxidative damage. Additionally, we conclude that ethylene inhibition (either high temperature or 1-MCP-induced) immediately after flowering (1 or 2 DPA) could potentially have positive impacts on early boll growth.

Towards estimating shade response of bermudagrass(Cynodon spp.)using field-based photosynthetic properties

Shade tolerance is a highly desirable trait when breeding new bermudagrass(Cynodon spp.)lines,but current screening methods can take many years to complete.There is a clear need for large-scale turfgrass breeding programs to reliably,accurately,and quickly predict shade tolerance in their germplasm.The objectives of this research were to:(i)build custom chambers to reproducibly estimate photosynthetic characteristics from turfgrass canopies at different light intensities and(ii)determine which photosynthetic characteristics are indicative of past shade performance.A custom-built chamber was constructed to determine average photosynthetic characteristics for the whole plant by studying the turfgrass canopy at natural leaf angles for light interception.Shade tolerant(11-T-56)and shade sensitive(Tifway)bermudagrass cultivars were used to examine the effectiveness of the chamber within an array of photosynthetic characteristics when the grasses were grown in full-sun and 73%shade environments.Light compensation point,chlorophyll content,quantum yield,dark respiration rate,and maximum quantum yield of photosystem II were evaluated in this trial.Based on the results of this study,the authors recommend that light compensation point or maximum quantum yield be further evaluated as an accurate indicator of shade tolerance when performed in the field on spring days with grasses grown in full sun or 73%shade environments.Lower Rd rates and ambient temperatures on spring days appear to minimize unexplained variance in the data,which would allow researchers to better detect genotypic differences during this season.