Growth,water status and photosynthesis in two maize (Zea mays L.) cultivars as affected by supplied nitrogen form and drought stress

Hydroponic experiments were conducted to investigate the effects of nitrogen form on plant growth,water status and photosynthetic characteristics under integrated root-zone drought stress (ir-ds) and non drought conditions (non-ds) with two hybrids of maize cultivars zhengdan 958 (zd958) and jundan 20(jd20). on the 12 th day of ir-ds,dry matter (dm) of total plant,shoot and root,relative water content (rwc),chlorophyll (chl.) content,net photosynthetic rate (p n),stomatal conductance (g s),transpiration rate (e) of both cultivars in all n forms treatments as well as intercellular co 2 concentration (c i) except nh 4-treatment were significantly decreased. however,lower dm production,rwc and p n as well as drought index (di) were observed for jd20 than zd958,thereby the later could be considered as a drought tolerance cultivar comparatively. by comparison with sole ammonium (nh 4 +),sole nitrate (no 3 -) and the mixture of nh 4 + and no 3 - both obviously increased dm of total plant,shoot and root,rwc,pn and chl. content while decreased g s,e and ci of both cultivars under drought. the effects of no 3 --supplied were superior than nh 4 +and no 3 - supplied in the above responses. these impacts were more predominant in zd958 than jd20. further analysis of variation indicated that the impact of n form treatment on most parameters measured except root dm were,in general,less than water regime while higher than cultivar. it is,therefore,concluded that an increase of ratio of no 3 - to nh 4 + in nutrition solution could lead to an enhancement in leaf rwc and photosynthesis of both cultivars subjected to ir-ds,then result in biomass increase,thus alleviate of damage from drought due to their obvious drought-resistance function based on its nutritive role,especially for a drought tolerant cultivar.