The Correlations Between Leaf Anatomical Characteristics And Photosynthetic Capacity And Drought Tolerance In Seven Sugarcane Cultivars

Sugarcane(Saccharum officinarum L)is an important sugar-production crop,a typical C4 plant with high photosynthetic capacity.Presently,the climate warming and severe drought have huge impact on the production of sugarcane.There is an important task in agriculture in subtropical and tropical regions to breed drought-tolerant sugarcane cultivars.Seven sugarcane cultivars were chosen and cultivated in barrels with sufficient water and nutrient supply,including high drought-tolerant cultivars GT11,GT47,medium drought-tolerant cultivars GT46,GT49 and ROC22 and low drought-tolerant cultivars G98-56,YUE60.We measured leaf anatomy,leaf turgor loss point as an indicator of drought tolerance and gas exchange properties from these cultivated plants,Comparing the differences between them.Photosynthetic performance and hydraulic capacity were monitored in sugarcane cultivars with different drought-tolerance under water stress and during recovery following rewatering.In this paper,we investigated the coordination between water supply and carbon assimilation in sugarcane cultivars with different drought-tolerance.The results show that,1)The leaf thickness,epidermis thickness and mesophyll thickness decrease gradually from high,medium to low drought-tolerant cultivars.2)Vein density was significantly higher in high drought-tolerant cultivars than in low-tolerant cultivars.Stomatal density and vein density were positively related to net photosynthetic rate.3)The leaves of high drought tolerance cultivars had higher ratio of bundle sheath area to mesophyll area on cross section basis.This ratio was also correlated positively with net photosynthetic rate,water use efficiency and negatively with the leaf tugor loss point.4)The capacity of leaf resistance to desiccation was positively related to net photosynthetic rate,which contradicts the conventional knowledge of the trade-off between plant productivity and stress resistance.5)The leaf water transport capacity was positively related to net photosynthetic rate and stomatal conductance.6)During the drought treatment,the photosynthetic capacity and leaf hydraulic conductance sharply declined and after rewatering they could recover in high drought-tolerant cultivars not in low-tolerant cultivars.Photosystem II(PSII)was irreversibly damaged in low-tolerant cultivars.In conclusion,the sugarcane cultivars with high drought tolerance had particular water and carbon assimilation advantages.The drought tolerance and photosynthetic capacity were coordinated in sugarcane cultivars.Leaf water transportation capacity,photosynthetic capacity and gas exchange characteristics had a collaborative relationship.When the high drought-tolerant cultivars experienced the drought treatment,their leaf hydraulic system and photosynthetic function were able to recover to control levels after rewatering for a week.The findings of the present study would have important implications for the breeding of drought-tolerant sugarcane cultivars and provide new evidence to explain high photosynthetic efficiency in C4 grasses.