Leaf Nitrogen Content, Photosynthesis and Radiation Use Efficiency in Peanut1

Supplemental Far-Red Light Stimulates Lettuce Growth: Disentangling Morphological and Physiological Effects

Light-emitting diodes allow for the application of specific wavelengths of light to induce various morphological and physiological responses. In lettuce (Lactuca sativa), far-red light (700-800 nm) is integral to initiating shade responses which can increase plant growth. In the first of two studies, plants were grown with a similar photosynthetic photon flux density (PPFD) but different intensities of far-red light. The second study used perpendicular gradients of far-red light and PPFD, allowing for examination of interactive effects. The far-red gradient study revealed that increasing supplemental far-red light increased leaf length and width, which was associated with increased projected canopy size (PCS). The higher PCS was associated with increased cumulative incident light received by plants, which increased dry matter accumulation. In the perpendicular gradient study, far-red light was 57% and 183% more effective at increasing the amount of light received by the plant, as well as 92.5% and 162% more effective at increasing plant biomass at the early and late harvests, respectively, as compared to PPFD. Light use efficiency (LUE, biomass/mol incident light) was generally negatively correlated with specific leaf area (SLA). Far-red light provided by LEDs increases the canopy size to capture more light to drive photosynthesis and shows promise for inclusion in the growth light spectrum for lettuce under sole-source lighting.

Heritability and correlation for nitrogen (N2) fixation and related traits in peanut (Arachis hypogaea L.)

The objectives of this study were to estimate broad sense heritability for N2 fixation and related traits and agronomic traits and evaluate correlations among these traits. Seventy four progenies in the F, generation previously selected in the F4 generation for high and low performance for N fixation and related traits were tested for N2 fixation and related traits and their agronomic performances. A non-nodulating line was also included as a reference crop for nitrogen determination. The experiment was carried out under limited soil nitrogen conditions. A randomized complete block design with four replications was used. Data were recorded for leaf color score, nodule dry weight, top dry weight, fixed nitrogen, pod number, pod weight, seed weight, seed size, shelling percentage and harvest index. Most heritability estimates for N2 fixation and related traits were moderate and high ranging from 0.33 to 1.00 except one low estimate (0.33). Most heritability estimates for agronomic traits were also moderate and high ranging from 0.37 to 1.00 except two low estimates (0.37 and 0.50). High heritability estimates in the F5 generation indicated that genetic variations of this population after divergence selection in the F4 generation are conserved and further selection for N2 fixation and agronomic traits in this population is possible when individual characters are considered. High and positive correlations among fixed nitrogen and its components were found indicating that increase in one trait can increase others. Correlations between N2 fixation and pod yield were low and varied depending on crosses suggesting that selection for both N2 fixation and pod yield is essential.