364 FUNDAMENTALS OF FRUIT PRODUCTION 



though in other instances considerable damage followed a temperature of 25.5°. 

 It should be recalled that there is practical unanimity among investigators that 

 rapid thawing is not in itself injurious, but there is no evidence as to the effects 

 of Hght on frozen tissue. Light is known to increase permeability and may well 

 be conceived to prevent the return to the cells of water which has been withdrawn 

 upon freezing, thus causing injury to tissues which otherwise would recover 

 their normal state. The common conviction among practical horticulturists 

 that rapid thawing is injurious may be founded on observations of the effect 

 of light on frozen tissue. Furthermore, the effects of the duration of exposure to 

 a given temperature have not been established definitely. 



Signs of Damage. — The thermometer, evidently, frequently fails to 

 give close or reliable indication of the amount of damage a frost has 

 inflicted. A fairly close estimate may be made, ordinarily, late in the 

 forenoon following a freeze, by an examination of the buds themselves. 



The pistils are the parts most readily affected in the blossom, becoming, when 

 damaged, wilted and discolored, though the bud may unfold its petals and 

 stamens. Curiously, in April, 1920, at Columbia, Mo., a temperature of 14°F. 

 when Jonathan apple blossoms were fairly well advanced seemed to damage, not 

 the pistils, but the stamens which turned orange in color, and the effects also be- 

 came evident on the stems near the purse. A similar condition, though less 

 pronounced, has been observed in the Willamette valley in Oregon. Sometimes 

 the petals are dwarfed but the bud otherwise uninjured. In peaches advanced 

 beyond the blossoming stage. Chandler^* states that the veins surrounding the 

 seed are the most tender, followed in order by the kernel and the flesh. Chandler 

 suggests that the greater tenderness of the seed may be correlated with the differ- 

 ence in sap density. The young seeds of the apple seem particularly tender and 

 after a frost they frequently are brown while the flesh is apparently undamaged. 



Paddock and Whipple^^^ state that after fertihzation has occurred apple 

 blossoms may survive some injury to the seeds though blossoms of the stone 

 fruits frozen to the extent that the basal part of the pistil is damaged rarely set 

 fruit. When interior apple tissues outside the seed cavities are damaged the 

 fruit does not mature. In this particular case, they say, the injury becomes 

 apparent early, in a yellowing of the tissues around the stem end of the fruit. 

 Seedless apples, particularly of some varieties, frequently develop to maturity 

 but generally are somewhat smaller than those with seeds. The same writers 

 state that the pear will mature fruit after showing still more injury than the 

 apple. In the young fruit they find much the same conditions holding, though 

 the stone fruits are said not to show injury which is confined to the seed cavity 

 until the time of the final swelling just before ripening, when the injured fruit 

 will show gummy exudations and ripen abnormally or it may drop before ripen- 

 ing. When the injury ismoreextensivethey drop shortly after blossoming. Apples 

 and pears survive injury to the seeds alone and in most cases with no other visible 

 evidence of damage. Apples injured outside the seed cavity do not mature but 

 pears so injured develop abnormally through enlargement of what would ordi- 

 narily be the neck of the fruit. This enlargement, together with the retarded 

 development of the parts surrounding the core, results in the familiar " bullneck." 



