Abstract: 【Objective】 The objective of this study is to reveal the effect of different environmental factors on grain protein content (GPC) of naked barley, to understand the relationship between naked barley GPC distribution characteristics and environmental factors, and to get clear on GPC acclimation of naked barley varieties from different areas to the environment of the Qinghai-Tibet plateau. 【Method】 Based on the method of agronomy combined with geography, naked barley GPC distribution characteristics in Qinghai-Tibet plateau was studied. 【Result】 Along the horizontal direction in Qinghai-Tibet plateau, GPC spatial distribution characteristics of naked barley varieties appeared in a macrocosm trend of high-in-south and low-in-north with a staggered pattern, and there developed two regions of higher GPC. One of the regions of higher GPC exists between the area with longitudes from 100.0°E to 102.5°E and with latitudes from 35.0°N to 37.5°N. And the average GPC of barley varieties in this region is (13.1163±0.5939)% in north-eastern Qinghai-Tibet plateau with distribution centers including Gonghe County, Guide County, Menyuan County and Tongde County in Qinghai Province, and Hezuo County in Gansu Province. Another region of higher GPC existed between the area with longitudes from 86.0°E to 92.0°E and with latitudes from 28.0°N to 29.0°N. And the average GPC of barley varieties in this region is (12.8715±0.6609)% in south-central Qinghai-Tibet plateau with distribution centers including Gongga County, Lazi County, Nimu County, Zhanang County, Nielamu County, Duilongdeiqing County, Sangri County and Kangma County in Tibet. Along the vertical direction with altitudes, GPC distribution pattern appeared in shape of inverted letter N. The average GPC value is (10.8650±1.8600)% at the altitudes below 3 000 m. GPC gradually decreased with altitude increasing, and then reached to the lower value at the altitudes from 3 000 m to 3 300 m. And GPC gradually increased with altitude increasing at the altitudes above from 3 000 m to 3 300 m, and then reached to the highest value at the altitudes from 3 600 m to 3 900 m with average GPC value of (10.8937±2.0719)%. Hereafter, GPC of barley varieties decreased gradually with altitude increasing. The magnitude of effect of environmental factors on naked barley GPC follows an order of soil available N content > sunshine hours during the growth period from heading to maturation > average diurnal temperature range during the growth period from seedling from tiller > average diurnal temperature range during the growth period from tiller to elongation > relative humidity during the growth period from elongation to heading. 【Conclusion】 Soil factors are the main environmental factors with the greatest impact on GPC, and followed by climatic factors, the effect of geographical factors on GPC is not apparent. Soil available N content is the main soil factor influencing barley GPC, and sunshine hours during the growth period from heading to maturation, average diurnal temperature range during the growth period from seedling from tiller, average diurnal temperature range during the growth period from tiller to elongation and relative humidity during the growth period from elongation to heading are the main climatic factors. Barley GPC increased with the increase of average diurnal temperature range during the growth period from tiller to elongation and relative humidity during the growth period from elongation to heading, though decreased significantly with the increase of sunshine hours during the growth period from heading to maturation and average diurnal temperature range during the growth period from seedling to tiller and soil available N content.

Key words: Qinghai-Tibet plateau, naked barley, protein content, spatial distribution regulation, environmental factor