Volume 23, Issue 2
February 1946, pages 73-112
pp 73-78 February 1946
The investigation deals with the effect of different photoperiodic treatments (6, 12, 18 and 24 hours daily), on sex expression inZea mays plants grown both under low N (normal) and high nitrogen (additional) conditions.
Twelve-hours’ photoperiod plants were characterised with normal staminate and carpellate inflorescences. Under 6-hour photoperiod a conspicuous change was effected in tassels; many spikelets took up pistillate forms leading to grain formation. In long photoperiods contrariwise, reversal took place in ears where good many male spikelets developed in place of the carpellate ones.
A small change from staminate character to pistillate one also took place under long photoperiods. This is explained on the greater stability of the female characters inZea mays than those of males.
Sex modifications were also initiated by heavy nitrogen nutrition to plants. This condition accelerated the change from maleness to femaleness in tassels but caused a relative inhibition in the sex reversal in the ear.
pp 79-85 February 1946
pp 86-99 February 1946
A study has been made of the amino-acid changes taking place during protein regeneration in seedlings ofDolichos biflorus, Phaseolus mungo andCicer arietinum.
The first metabolic change observed is the rapid solubilization and hydrolytic breakdown of the seed protein. The soluble nitrogen reaches a maximum within 24 hours of germination. This is followed by hydrolysis of protein and the conversion of the greater part of it into amino-acids and subsequently to amides. During seedling growth all amino-acid fractions decrease with the exception of the dicarboxylic acids and their amides. Both asparagine and glutamine increase to many times their initial values but the quantity of glutamine is in all cases much smaller than that of asparagine. From the conditions under which the plants were grown asparagine formation must be considered a normal stage in protein regeneration in plants.
The presence in the seedlings of a third amide in addition to asparagine and glutamine can be inferred from the following facts:
The amide N in the aqueous extracts of the seedlings is greater than can be accounted for by the sum of asparagine and glutamine amide N present.
Amides are present in excess of the dicarboxylic acids, especially inDolichos biflorus andPhaseolus mungo.
InDolichos biflorus andPhaseolus mungo asparagine accumulation takes place without a corresponding increase in dicarboxylic acids indicating the possibility of a conversion of glutamic acid into aspartic acid,
The strikingly rapid disappearance of arginine observed in some of the seedlings suggests that this amino-acid plays a special role as a precursor of amides.
pp 100-112 February 1946
The thermophilic bacteriaBacillus thermophilus, B. aerothermophilus andB. thermoacidurans produce powerful proteinases which can be detected in the culture filtrates.
These proteinases resemble tryptases in their optimum hydrogenion requirements and hydrolyse gelatin and casein readily and albumins sparingly, unless the albumin has been previously denatured.
In addition to the proteinases these thermophilic bacteria also produce a polypeptidase capable of hydrolysing peptone, but this enzyme appears in culture filtrates much later than the proteinases.
Velocity of gelatin hydrolysis by these proteinases varies directly as the square root of time and percentage of hydrolysis varies directly with the enzyme concentration.
Relationship of substrate concentration and rate of hydrolysis shows that in case of gelatin Michaelis and Menton’s equation is applicable and that an intermediate enzyme-substrate complex consisting of one molecule each of the enzyme and the substrate is probably formed before the substrate is hydrolysed.