Different growing strategies of two winter wheat cultivars under rainfed conditions during dry years in North China Plain

The North China Plain(NCP)is a severe water shortage region,especially during the wheat growing season.Understanding the response of grain yield and water availability in winter wheat cultivars(Triticum aestivum L.)is important to adjust planting structure under groundwater reducible exploitation in rainfed dry years of NCP.Field experiments were conducted at the Luancheng Agroecosystem Experiment Station of the Chinese Academy of Sciences,Hebei,China.Two different drought resistant winter wheat cultivars(Jinmai47 and Shiluan02-1)were grown under rainfed conditions during four years of 2010-2011,2011-2012,2012-2013 and 2013-2014.Grain yield and its components,aboveground biomass(AB),dry matter accumulation translocation efficiency,water consumption,water use efficiency at field scale,and photosynthetic characteristics were measured.The results showed that Jinmai47 rapidly accumulated AB by higher tiller and photosynthetic potential comparing with those of Shiluan02-1.Its grain yield was 16.49%higher than that of the drought-sensitive winter wheat variety Shiluan02-1 during the four rainfed years.However,the dry matter remobilization efficiency(DMRE)and contribution of dry matter remobilization from heading stage to maturity stage to grain(CDMRE)of Shiluan02-1 was higher than those of Jinmai47.The average water use efficiency at grain yield level(WUEy),WUE at aboveground biomass level(WUEab),and WUE at grain yield under rainy conditions(WUEr)of Jinmai47 were 11.08%,16.41%,and 17.21%higher than those of Shiluan02-1.There was a significant difference in the WUEab and WUEr between the two wheat cultivars.The two wheat varieties under drought condition have different growing strategies.Jinmai47 has more tiller number,earlier vigor,and higher AB than Shiluan02-1,helping it to adapt to the fluctuations in the environment.

Responses in gross primary production of Stipa krylovii and Allium polyrhizum to a temporal rainfall in a temperate grassland of Inner Mongolia, China

In the arid and semi-arid areas of China, rainfall and drought affect the growth and photosynthetic activities of plants.Gross primary productivity(GPP) is one of the most important indices that measure the photosynthetic ability of plants.This paper focused on the GPP of two representative grassland species(Stipa krylovii Roshev.and Allium polyrhizum Turcz.ex Regel) to demonstrate the effect of a temporal rainfall on the two species.Our research was conducted in a temperate grassland in New Barag Right Banner, Hulun Buir City, Inner Mongolia Autonomous Region of China, in a dry year 2015.We measured net ecosystem productivity(NEP) and ecosystem respiration flux(ER) using a transparent chamber system and monitored the photosynthetically active radiation(PAR), air and soil temperature and humidity simultaneously.Based on the measured values of NEP and ER, we calculated the GPP of the two species before and after the rainfall.The saturated GPP per aboveground biomass(GPPAGB) of A.polyrhizum remarkably increased from 0.033(±0.018) to 0.185(±0.055) μmol CO2/(gdw·s) by 5.6-fold and that of S.krylovii decreased from 0.068(±0.021) to 0.034(±0.011) μmol CO2/(gdw·s) by 0.5-fold on the 1st and 2nd d after a 9.1 mm rainfall event compared to the values before the rainfall at low temperatures below 35℃.However, on the 1st and 2nd d after the rainfall, both of the saturated GPPAGB values of S.krylovii and A.polyrhizum were significantly lower at high temperatures above 35℃(0.018(±0.007) and 0.110(±0.061) μmol CO2/(gdw·s), respectively) than at low temperatures below 35℃(0.034(±0.011) and 0.185(±0.055) μmol CO2/(gdw·s), respectively).The results showed that the GPP responses to the temporal rainfall differed between S.krylovii and A.polyrhizum and strongly negative influenced by temperature.The temporal rainfall seems to be more effective on the GPP of A.polyrhizum than S.krylovii.These differences might be related to the different physiological and structural features, the coexistence of the species and their species-specific survival strategies.