34 MASS. EXPERIMENT STATION BULLETIN 355 



Other samples were obtained from the Waltham Field Station to determine 

 what, if any, is the residual effect of previous applications of iron, copper, man- 

 ganese, and iodine. These samples included greenhouse tomatoes and celery. 



"Dark Center" in turnips and "cracked" celery have apparently been shown 

 to be the result of a deficiency of boron in the soil though the condition is remedied 

 by small applications. Fertilization experiments conducted at the Waltham 

 Field Station, to determine the location of the boron in the plant and therefore 

 perhaps its function as well as the residual effects, produced 30 samples for this 

 project. At the present time there is some feeling that the residual effects of 

 boron remaining in the soil may be harmful. Three samples of soil have been 

 taken to determine whether or not there is an appreciable accumulation. 



The collection of these samples as well as their analysis is practically complete 

 and this information will be available soon and, it is believed, useful. 



Lignin and Its Relation to the Absorption of Minerals by Plants. (Emmett 

 Bennett.) In order to determine the effect of the decomposition products of 

 lignin, this substance was mixed with soils of high and low content of organic 

 matter, in the ratio of one to ten by weight, and allowed to decompose. Con- 

 ductivity and surface tension measurements will be made after changes have had 

 time to occur. 



The electrodialysis of lignin in a Mattson cell produced diffusates different 

 in color and odor. The anode diffusate was dark brown in color and had a pleas- 

 ant odor, while the cathode diffusate was practically colorless and had a fishy 

 odor. 



These differences together with positive qualitative tests for lignin in the anode 

 diffusate suggested a partial separation of this material. These observations would 

 seem to indicate that lignin was more soluble than is generally supposed, and that 

 it consisted of some acidic fractions — all of which would give us a better under- 

 standing of its chemical nature and its action on the soil. 



Precursors of Lignin. Interest in the general chemistry of lignin and its inter- 

 relationship with other plant constituents, has come about because of the part 

 this substance plays in the growth, nutrition, and decomposition of farm crops. 

 This investigation was designed to gain a better understanding of the formation 

 of lignin in the plant. 



Pectin has been suggested as a possible parent substance, principally because 

 it has been shown that so-called lignified tissues contain relatively large amounts 

 of lignin and hemicelluloses, with only traces of pectin. On the other hand non- 

 lignified tissues contain relatively large amounts of pectin, small amounts of 

 hemicelluloses, and only traces of lignin. A two-year study of the seasonal varia- 

 tions in content of pectin, hemicelluloses, and lignin was conducted with a legume 

 (red clover, Trifolium pratense) and a grass (Kentucky blue grass, Poa pratensis), 

 taken at successive stages of growth. 



Seasonal trends of both plants indicated that the content of pectin was rel- 

 atively constant, while that of the hemicelluloses and lignin increased. In mature 

 red clover the content of these constituents was of approximately the same 

 general order, while in mature Kentucky blue grass a trace of pectin was asso- 

 ciated with twenty-five times as much hemicelluloses and eight times as much 

 lignin. A relationship between these substances was not apparent in either 

 plant. The seasonal variations, however, showed that the same content of lignin 

 in different plants may be associated with variable quantities of pectin, and that 

 the presence of a trace of this substance does not necessarily signify that a trans- 

 formation has occurred. It seems, therefore, that differences in the proportion 

 of pectin, hemicelluloses, and lignin in different plants are probably due to varia- 

 tions in cell structure rather than to transformation. 



