Manganese Toxicity And Iron Effect In Saccharum Spontaneum Linn

Saccharum officinarum L.is the most important sugar crop in our country.Guangxi is located in the tropics and subtropics where have rich water,hot resources and obvious advantages of developing the sugarcane industry.In addition,the sugarcane industry has been developing into a pillar industry of Guangxi,and it also plays a key role in the whole economy.However,the chlorosis of sugarcane seedlings has been threatening the sugarcane industry heavily.The aim of this study was to use Saccharum spontaneum Linn as an energy plant to provide scientific references by revealing the chlorosis of sugarcane seedlings under Mn stress.Under solution culture condition,the effects of Hign Mn-induce a yellowing of young leaves and on Fe-Mn nutrient elements,absorption and distribution which grew in high Mn concentration as they were studied.The paper also studied the influence of different manganic forms on spontaneum plant growth,alongside Fe-Mn nutrient absorption under manganese stress with a soil culture experiment.The paper also studied the effect of sugarcane stalks on different manganic forms by soil culture experiment.The last part studied how to reduce and prevent the chlorosis under high Mn stress.The main obtained results are as follows.1.After 10 days' 25.0?600.0 ?mol·L-1 MnCl2 treatment,the spontaneum plant growth was inhibited and the young leaves became yellow.Among three strains,the chlorophyll content of gxs-87-16 was 14%-85%less than CK,Chuanyuezhong reduced by 14%-81%,and Linyun reduced by 8%?85%.The result shows that High manganese induces the decline of chlorophyll content.2.After 10 days' 0?600.0 ?mol·L-1 MnCl2 treatment,the highest percentage of Mn content in shoots of spontanuem was in the sheaths.This was followed by old leaves,young leaves,and the stem.Lingyun and gxs-87-16 have less Mn content,the Mn content of both roots decreased under high Mn stress.It could indicate that Linyun and gxs-87-16 are more sensitive to manganese.Chuanyuezhong has the highest Mn content among the three strains,and the Mn content of roots increased one hundred and two fold more than CK.It may prove that Chuanyuezhong has a high tolerance to Mn.The Mn content of shoots decreased from top to bottom under high Mn stress.3.After 10 days' 0?0.6 mmol·L-1 MnCl2 treatment,the highest percentage of Fe content in shoots of spontanuem was in old leaves.This was followed by sheaths,young leaves,and the stem.High Mn could significantly decrease the Active Fe and Fe contents of Linyun and gxs-87-16.It shows that Linyun and gxs-87-16 are more sensitive to manganese but Chuanyuezhong has a high tolerance to Mn.The Mn content of the stem decreased from bottom to top under high Mn stress.This is contrary to Mn content.4.After 5?1360 mg·kg-1 Mn was added to the soil for 4 months,the exchangeable Mn content increased by 240?22726 fold more than CK,while the labile reduction Mn content only increased by 3?22 fold more than CK.There is a remarkable relationship between exchangeable Mn content of soil and Mn content of the shoots of spontanuem.It indicates that plants could absorb the exchangeable Mn of soil.These results show that exchangeable Mn is a reflection of Mn toxicity in the soil.5.The process of decay of sugarcane stalks in soil can increase the exchangeable Mn of soil remarkably,particularly the sugarcane stalks under high Mn content.This result indicates that returning sugarcane stalks to the field could be the reason which causes the chlorosis of ratoon sugarcane.6.Fe supply before or after any signs of yellowing can increase the chlorophyll and active Fe contents stress resistance under high Mn stress significantly.Spontanuem plants can also effectively utilise Fe(OH)3 and increase stress resistance under high Mn stress.Increasing the Mn/Fe ratio in nutrient solution could also raise the chlorophyll and active Fe content.In addition,foliar-spraying Fe before or after any signs of yellowing has the same function as above.Therefore,increasing the supply of Fe can effectively prevent or alleviate the Mn-induced chlorosis of sugarcane.In conclusion,high manganese induces the chorosis of sugarcane.The highest percentage of Mn content in shoots of spontanuem were the sheaths,and the Mn content of shoots decreased from top to bottom under high Mn stress.In contrast,the highest percentage of Fe content in shoots of spontanuem was old leaves and the Mn content of the stem decreased from bottom to top under high Mn stress.The results indicate that Lingyun and gxs-87-16 are more sensitive to manganese but Chuanyuezhong has the highest Mn tolerance.The results also indicate Spontanuem plants could absorb the exchangeable Mn of soil.It shows that exchangeable Mn is a reflection of Mn toxicity in the soil and that returning sugarcane stalks to field could increase the exchangeable Mn and also may be a reason which causes the chlorosis of ratoon sugarcane.Finally,increasing the supply of Fe can effectively prevent or alleviate the Mn-induced chlorosis of sugarcane.