Source and sink development during kernel filling of two spring wheats as affected by root size and cytokinin applications

The effects of partial root removal and cytokinin applications at different times during kernel filling were examined at two contrasting wheat genotypes grown in controlled environmental conditions. Treatments affected the development of leaves, and grain setting, but hardly grain growth; the influence strongly depended on time, but not on genotype. Cutting off roots ?early”? after heading caused immediate damage, especially in the lower leaves. Later on, chlorophyll decomposition and loss of green area was accelerated. ?Early”? cytokinin applications were not able to prevent these effects. If root size was reduced at a ?medium late”? or ?late”? stage no spontaneous effects were observed, but leaf senescence was more drastic, the later the treatments were carried out. Enhancement of senescence due to root removal, could generally be inhibited by (medium) ?late”? cytokinin applications. As to grain setting, ?early”? cytokinin applications could not counteract the reduction induced by ?early”? root removal. In most of the trials there was no evidence that root removal or cytokinin applications affected grain growth. Some secondary effects of the treatments on root growth are discussed with regard to the importance of root system as a site of cytokinin synthesis during grain filling.     

Gas Exchange of Five Warm‐Season Grain Legumes and their Susceptibility to Heat Stress

Objective of this study was to compare the heat stress performance of four pulses from dry and hot areas (mungbeans, limabeans, and teparybeans and cowpeas) with that of soybeans. Two experiments were conducted in growth chambers, and data were pooled because results of both experiments were similar. Plants were raised up to flowering at 24/17 °C (day/night) and were then either exposed to these temperatures until maturity or stressed with 33/24 °C for 2 weeks starting at day 1 or 15 after onset of flowering (early vs. late stress). Before, during and after these stress intervals, gas exchange of representative upper leaves was examined; additionally, immediate effects of increasing leaf temperatures from 24 to 32 or 40 °C on chlorophyll fluorescence were assessed. Without heat stress rates of photosynthesis (P_n), and of transpiration (TR), stomatal and mesophyll conductance (g_s, g_m) and intrinsic transpiration efficiency (iTE) differed significantly among the five crops at each date. However, because of crop‐specific time‐courses ranking among unstressed crops was instable with time, so values were integrated or averaged over time. This procedure revealed high P_n potentials in mung‐ and teparybeans and high iTE values in limabeans compared to the other crops. Heat stress lowered P_n and g_s considerably, but increased TR in all five crops. Relative lowering of P_n during heat stress displayed a crop‐specific pattern with limabeans being least susceptible to both early and late heat stress, while cowpeas were highly susceptible to early stress. Effects on P_n were mainly attributable to lowering of g_s and only in part to g_m. The latter was supported by very small changes (<10 %) of various chlorophyll fluorescence signals shortly after raising leaf temperature to 32 °C in all species. However, in limabeans, a decreased electron transport rate (e‐rate, ?18 %) and an increased non‐photochemical quenching (Q_N, +16 %) pointed to an adaptive mechanism to avoid oxidative strains under heat. Leaf temperatures of 40 °C immediately provoked stronger changes in all fluorescence signals than 32 °C; substantial damages at 40 °C were indicated by effective quantum yield, photochemical quenching and ratio of fluorescence decrease in mungbeans and low ones in cowpeas and soybeans. Nevertheless, some adaptive responses of e‐rates and Q_N were observed in all crops and were most expressed in limabeans.     

Consumption of a novel dietary formula of plant sterol esters of canola oil fatty acids, in a canola oil matrix containing 1,3-diacylglycerol, reduces oxidative stress in atherosclerotic apolipoprotein E-deficient mice

The antiatherogenic properties of a novel dietary formula (PS-CO) of plant sterol esters of fatty acids, produced by enzymatic interesterification of plant sterols with canola oil (CO), in a CO matrix containing 1,3-diacylglycerol, were evaluated in apolipoprotein E-deficient mice. PS-CO consumption strongly tended to lower total plasma cholesterol levels by 21%, compared to the placebo group. Blood triglycerides were reduced by 38% and 36% compared to CO and placebo-fed mice, respectively. Serum lipid peroxide levels were lowered following PS-CO administration by 62% and 63%, compared to CO and placebo administration, respectively. Unlike CO supplementation, PS-CO consumption preserved serum paraoxonase (PON1) activity. Mouse peritoneal macrophages from PS-CO-fed mice exhibited reduced cellular uptake of oxidized-LDL compared to those from placebo-fed mice and demonstrated a tendency toward a decreased capability to release superoxide anions. These findings indicate that PS-CO supplementation is beneficial in reducing serum lipid levels, and serum and macrophage oxidative stress, thus contributing to the reduction in atherogenic risk factors.