Effects Of Simulated Acid Rain On The Growth, Yield And Quality Of Crops

By means of a scheme for completely randomized selection of plots, tow field experiments are carried out in the Nanjing region to examine the effect of simulated acid rain on the growth, yield and quality of rape (Brassica napus L.) and wheat (Yamgmai 12) in conjunction with their mechanisms so as to provide scientific basises for preventing and controlling the damage to crops from the disaster. Results show that 1) simulated acid rain stress had considerable effect on the two crops growth/development in such a way that the plant height was obviously shorten, the synthesis of photosynthetic pigments was damage, the leaf area was suppressed, the leaf senescence was accelerated and the specific fresh leaf was greatly declined with visible injury was obsorved when pH=3.1 and pH=2.5 operation were conducted separately. 2) yield analysis indicates that with increased of acidity, rape yield increased at first, and then decreased with the pH=4.1 concentration could be taken as its threshold value, however, wheat yield recuced drastically under the acid stress, the effective spike number, spike weight, grains per spike, 1000-grain weight and filled grant rate as well as grant yield were significant lower than CK when pH≤3.5. 3) study of quality indexes suggest that the rape total free amino acid and soluble protein were increased first,and then decreased as acid rain acidity become stronger, their threshold value were at pH =4.1-3.1and pH=5.1-4.1. The syntheses of total free amino acid and soluble protein were promoted under weak acid rain condition, but in the opposite case, the syntheses are strongly inhibited by MAR and NAR, with the latter being stronger. Contents of total free amino acid and soluble protein in wheat leaves decreased as the acidity became stronger, and they were significantly lower than those in the CK case at the acid rain pH≤3.5 and also pH≤4.5, in the graint case, both of them were also reduced, and were significantly lower than CK when the acid rain pH≤4.5 and pH≤2.5, saparately. The content of rape educed sugar follows a trend of increased at first, and then decreased as acid rain pH valuce decreased, with its threshold value was between pH=3.1 to pH=1.5, however, the soluble suagar content was reduced consistently, and significantly lower than CK when pH≤5.1.The synthesis of soluble sugar and reduced sugar in wheat leaf was suppressed under acid rain stress, and the suppression was more apparent when pH≤3.5. Similar to the wheat leaf case, both of the soluble sugar and reduced sugar in wheat graint was also decreased, and the soluble sugar was significantly lower than CK when pH≤4.5, but the reduced sugar was not reach to statistically significant with CK under acid rain treatments. Acid rain stress could reduce the content of crude fat in the rape seeds, and with increased acidity their drop ranges would be enlarged. Under the impact of the three kinds of acid rain simulations, the content of rape crude fat follows a trend of increase at first, and then decrease as a function of enhancing pH values. Under stronger acidity NAR and MAR inhibit the synthesis of crude fat, but SAR has weaker effect in comparison to them. With acid rain acidtity become stronger, the synthesis of rape seeds total acidity was supressed when pH≤3.1, and significantly decreased under pH=1.5 treatment. With the increase of acidity from CK (pH 7.0) to 1.5, these simulated acid rains cause stable grows in the total content of the rape glucosindate, and in the condition of stronger acidity, NAR and MAR have greater effect. The three kinds of acidity can reduce the content of oleic acid to some extent, but at pH≤4.1,the NAR promotes the synthesis of linoleic acid, linolenic acid and erucic acid more significantly, thus degrading the nutrient quality of the crop.