Respiratory changes in yam storage tissue (Dioscorea spp.) infested with Meloidogyne incognita using a novel technique for measuring oxygen uptake

The mechanism by which reduced-height genes, Rht₁ and Rht₂ influence yield and harvest index (HI) were investigated in dwarf (D, Rht₁Rht₂), semidwarf (SD-1 and SD-2, Rht₁rht₂ and rht₁Rht₂, respectively), and tall (T, rht₁rht₂) near-isogenic lines (isolines) derived from winter wheat cv. Burt. Dry matter accumulation, yield, and assimilation, distribution, and retention of ¹⁴C label from photosynthetic assimilation of ¹⁴CO₂, was followed in field-grown plants in Connecticut, USA. The relationships among the isolines were similar over the two years of study. The tall isoline ranked highest in grain yield and biomass, but had a small HI; SD-1 was similar to T in yield and biomass, but had the largest HI; SD-2 was similar to SD-1 in HI, but its yield and biomass were less than SD-1 and T; and D yielded the least grain and biomass and had a small HI similar to T. Following photosynthetic assimilation of ¹⁴CO₂ during grain filling, the distribution of ¹⁴C in ears at maturity was similar for SD-1, SD-2, and T. When labelled shortly after anthesis or late in grain filling, the distribution of ¹⁴C to the mature ear of D was less than that for other isolines. At maturity D also retained the smallest amount of the radioactivity initially assimilated. The low yield and HI of D may be related to its inability to retain photosynthate and distribute it to the grain. The SD-1, SD-2, and T isolines did not differ in retention at maturity of ¹⁴C in the whole plant. When labelled shortly after anthesis, stems of T retained more ¹⁴C, which may represent a tendency to sequester more photosynthate in its stems that would reduce its HI at maturity. In contrast, the yield of SD-2 was limited by photosynthetic capacity.     

Observations on the Regulation of Glutamate Dehydrogenase Activity in Coprinus lagopus

Extracts of the mycelium of Coprinus lagopus (sensu Buller)contain two glutamate dehydro-genases with different optimumpH values. One is assayed with nicotinamide adenine dinucleotide(NAD-GDH) and the other with nicotinamide adenine dinucleotidephosphate (NADP-GDH). Changes in specific activity of the enzymeswere investigated during the growth of both a monokaryon (H9)and a dikaryon (H9 x TC) in different media and after the transferof mycelium from one growth medium into another. In the lattercase the magnitude of the changes in enzyme activity could bealtered by modification of either the carbon or the nitrogensource in the transfer medium. It is concluded from the resultsobtained that neither glutamate nor the ammonium ion seems toregulate directly the synthesis of either enzyme. However, someof the results are in accordance with the view that a productof glucose metabolism represses the synthesis of the NAD-GDHand derepresses or induces that of the NADP-CDH and evidencethat this regulator is 2-oxoglutarate was obtained. It is alsoconcluded that the complete system of regulation must involvemore than one molecule.