Impacts of freeze-thaw processes on antioxidant activities and osmolyte contents of Syntrichia caninervis under different desert microhabitats

doi:10.17521/cjpe.2015.0050

Abstract

Abstract: Aims

Syntrichia caninervis, a typical drought-tolerant moss species found worldwide in various semiarid and arid regions, is the dominant species of soil crust mosses in the Gurbantünggüt Desert, which is a temperate northern desert of Central Asia. It appears able to endure frequent and intensive freeze-thaw cycles in the surface soil and maintain physiological functions active even under extreme low temperatures in winter. However, there have been few studies exploring the adaptive strategies of the species during freeze-thaw processes and interpreting well the phenomena. One of the major goals of this study was to investigate physiological regulatory mechanisms of the species when undergoing freezing-thawing periods and relevant antioxidant enzyme activities.

Methods

A series of microclimate and soil conditions were continuously monitored in the sampling sites starting from November 2013. The samples of the moss were collected during the early spring of 2014 from February to April and from three microhabitats including the sites under live shrub, under dead shrub and on an open ground. The moss samples were quickly treated in the field for keeping freshness and then brought to laboratory for measurement and analysis. The traits/characteristics that reflect physiological and biochemical activities were measured for analyzing responses of the species to freeze-thaw processes and for comparing the impacts of different habitats, which included water content, concentrations of proline, soluble sugar, soluble protein and malondialdehyde (MDA), as well as catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) activities.

Important findings

The results showed that, during different freeze-thaw periods, microhabitats and their interactions with alternative freeze-thaw processes significantly affect the contents of proline, soluble sugar, soluble protein and MDA in shoots of the species, as well as the enzyme activities of CAT, POD, and SOD. Extreme low temperature and drought caused significantly higher soluble sugar and MDA contents, higher CAT, POD and SOD activities, but lower soluble protein content, in snow covered period (February) and dry period (April) than the snow melting period (March). The existence of live shrub decreased temperature around the bushes during snow melting because of the effect of shade, causing increased contents of soluble sugar and MDA in moss shoots, when compared to those growing in the habitats under dead shrub and on open ground. However, live shrub could provide a moister environment for S. caninervis than dead shrub and exposed ground for the duration of desiccation. As the result, the proline content, soluble sugar content and MDA content of the species under the live shrub canopy were the lowest among the three habitats. Furthermore, the mosses lived on the exposed ground showed the highest antioxidant enzyme activities comparing to those under the dead shrub and living shrub. This may suggest that S. caninervis grown on exposed grounds has developed rather a specific adaptations for a harsher environment condition than that occurred in other two habitats.

Key words: bryophytes, biological soil crusts, antioxidant enzymes, osmoregulation substance, freezing-thawing periods

YIN Ben-Feng,ZHANG Yuan-Ming. Impacts of freeze-thaw processes on antioxidant activities and osmolyte contents of Syntrichia caninervis under different desert microhabitats[J]. Chin J Plan Ecolo, 2015, 39(5): 517-529.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2015.0050

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Figures/Tables 9

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项目 Item	活灌丛 Alive shrub	死灌丛 Dead shrub	裸露地 Exposed area
有机碳 Organic matter (g·kg^-1)	3.721 ± 0.318^a	3.898 ± 0.737^a	2.300 ± 0.574^b
全氮 Total nitrogen (g·kg^-1)	0.475 ± 0.073^a	0.495 ± 0.048^a	0.301 ± 0.047^b
全磷 Total phosphorus (g·kg^-1)	0.400 ± 0.014^ab	0.445 ± 0.013^a	0.394 ± 0.059^b
全钾 Total potassium (g·kg^-1)	13.119 ± 0.249^a	12.977 ± 0.127^a	12.194 ± 0.136^b
总盐 Total salt (g·kg^-1)	0.576 ± 0.018^a	0.567 ± 0.079^a	0.514 ± 0.045^a
pH值 pH value	7.936 ± 0.031^a	7.672 ± 0.036^b	7.652 ± 0.262^b
电导率 Electrical conductivity (μs·cm^-1)	0.131 ± 0.009^a	0.129 ± 0.008^a	0.125 ± 0.016^a
冻结期温度(日均温) Temperature in freezing periods (℃)	-9.36	-11.09	-11.67
融雪期温度(日均温) Temperature in snow melting periods (℃)	-2.18	2.81	2.82
春季中旬干旱无雨期温度(日均温) Temperature in dry environment (℃)	9.76	11.64	11.64

项目 Item	活灌丛 Alive shrub	死灌丛 Dead shrub	裸露地 Exposed area
有机碳 Organic matter (g·kg^-1)	3.721 ± 0.318^a	3.898 ± 0.737^a	2.300 ± 0.574^b
全氮 Total nitrogen (g·kg^-1)	0.475 ± 0.073^a	0.495 ± 0.048^a	0.301 ± 0.047^b
全磷 Total phosphorus (g·kg^-1)	0.400 ± 0.014^ab	0.445 ± 0.013^a	0.394 ± 0.059^b
全钾 Total potassium (g·kg^-1)	13.119 ± 0.249^a	12.977 ± 0.127^a	12.194 ± 0.136^b
总盐 Total salt (g·kg^-1)	0.576 ± 0.018^a	0.567 ± 0.079^a	0.514 ± 0.045^a
pH值 pH value	7.936 ± 0.031^a	7.672 ± 0.036^b	7.652 ± 0.262^b
电导率 Electrical conductivity (μs·cm^-1)	0.131 ± 0.009^a	0.129 ± 0.008^a	0.125 ± 0.016^a
冻结期温度(日均温) Temperature in freezing periods (℃)	-9.36	-11.09	-11.67
融雪期温度(日均温) Temperature in snow melting periods (℃)	-2.18	2.81	2.82
春季中旬干旱无雨期温度(日均温) Temperature in dry environment (℃)	9.76	11.64	11.64

因子 Factor	脯氨酸含量 Proline content	可溶性糖含量 Soluble sugar content	可溶性蛋白含量 Soluble proteins content	丙二醛含量 MDA content	超氧化物歧化酶活性 SOD activity	过氧化物酶活性 POD activity	过氧化氢酶活性 CAT activity
微生境 Microhabitats	37.695^**	1.841	41.663^**	5.488^*	122.556_**	45.145^**	22.239^**
冻融期 Freezing-thawing periods	266.579^**	919.016^**	325.679^**	1153.946^**	494.308^**	152.878^**	105.681^**
微生境×冻融期 Microhabitats × freezing-thawing periods	40.255^**	27.920^**	3.475^*	7.710^**	50.115^**	15.406^**	3.869^*

因子 Factor	脯氨酸含量 Proline content	可溶性糖含量 Soluble sugar content	可溶性蛋白含量 Soluble proteins content	丙二醛含量 MDA content	超氧化物歧化酶活性 SOD activity	过氧化物酶活性 POD activity	过氧化氢酶活性 CAT activity
微生境 Microhabitats	37.695^**	1.841	41.663^**	5.488^*	122.556_**	45.145^**	22.239^**
冻融期 Freezing-thawing periods	266.579^**	919.016^**	325.679^**	1153.946^**	494.308^**	152.878^**	105.681^**
微生境×冻融期 Microhabitats × freezing-thawing periods	40.255^**	27.920^**	3.475^*	7.710^**	50.115^**	15.406^**	3.869^*

变量 Variable	脯氨酸含量 Proline content	可溶性糖含量 Soluble sugar content	可溶性蛋白含量 Soluble proteins content	丙二醛含量 MDA content	超氧化物歧化酶活性 SOD activity	过氧化物酶活性 POD activity	过氧化氢酶活性 CAT activity
冬季低温冻结期 Freezing period
含水量 Water content	-0.191	0.737^**	0.861^**	-0.051	-0.915^**	-0.800^**	-0.803^**
温度 Temperature	-0.191	0.730^**	0.861^**	0.052	-0.899^**	-0.767^**	-0.797^**
融雪期 Snow melting period
含水量 Water content	0.172	0.462	0.515^*	0.747^**	-0.457	-0.668^**	-0.479
温度 Temperature	-0.008	-0.907^**	-0.696^**	-0.635^*	0.437	0.755^**	0.644^*
春季中旬干旱无雨期 Dry environment
含水量 Water content	-0.812**	-0.676^**	0.747^**	-0.764^**	-0.696^**	-0.758^**	-0.830^**
温度 Temperature	0.802**	0.601^*	-0.688^**	0.707^**	0.710^**	0.767^**	0.809^**