Diffusional and Biochemical Limitations to Photosynthesis Under Water Deficit for Field-Grown Cotton.

Water deficit stress limits net photosynthetic rate (A), but the relative sensitivities of underlying processes such as thylakoid reactions, ATP production, carbon fixation reactions, and carbon loss processes to water deficit stress in field-grown upland cotton require further exploration. Therefore, the objective of the present study was to assess (1) the diffusional and biochemical mechanisms associated with water deficit-induced declines in A and (2) associations between water deficit-induced variation in oxidative stress and energy dissipation for field-grown cotton. Water deficit stress was imposed for three weeks during the peak bloom stage of cotton development, causing significant reductions in leaf water potential and A.

Estimating yield-contributing physiological parameters of cotton using UAV-based imagery.

Lint yield in cotton is governed by light intercepted by the canopy (IPAR), radiation use efficiency (RUE), and harvest index (HI). However, the conventional methods of measuring these yield-governing physiological parameters are labor-intensive, time-consuming and requires destructive sampling. This study aimed to explore the use of low-cost and high-resolution UAV-based RGB and multispectral imagery 1) to estimate fraction of IPAR (IPAR), RUE, and biomass throughout the season, 2) to estimate lint yield using the cotton fiber index (CFI), and 3) to determine the potential use of biomass and lint yield models for estimating cotton HI.

Stereoselectivity in (Acyloxy)borane-Catalyzed Mukaiyama Aldol Reactions.

The origin of diastereo- and enantioselectivity in a Lewis acid-catalyzed Mukaiyama aldol reaction is investigated using a combination of dispersion corrected DFT calculations and transition state force fields (TSFF) developed using the quantum guided molecular mechanics (Q2MM) method. The reaction proceeds via a closed transition structure involving a nontraditional hydrogen bond that is 3.3 kJ/mol lower in energy than the corresponding open transition structure.

Internal and external stereoisomers of squaraine rotaxane endoperoxide: synthesis, chemical differences, and structural revision.

Photooxygenation of permanently interlocked squaraine rotaxanes with anthracene-containing macrocycles produces the corresponding squaraine rotaxane endoperoxides (SREPs) quantitatively. SREPs are stored at low temperature, and upon warming, they undergo clean cycloreversion, releasing singlet oxygen and emitting light. The structural elucidation in 2010 assigned the structure as the SREP-int stereoisomer, with the endoperoxide unit directed inside the macrocycle cavity.

Diastereoselectivity in Lewis-acid-catalyzed Mukaiyama aldol reactions: a DFT study.

The basis for diastereoselectivity in Lewis-acid-catalyzed Mukaiyama aldol reactions was studied using density functional theory. By exploring the conformations of the transition structures for the diastereodifferentiating step of seven different reactions, simple models were generated. The effects of varying the substituents on the enol carbon and the α-carbon of the silyl enol ether from methyl to tert-butyl groups and the substituent on the aldehyde from methyl to phenyl groups were investigated by comparison of the transition structures for different reactions.