2000,19 (6) 1-6 Chinese Journal of Ecology

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1 2000,19 (6) 1-6 Chinese Journal of Ecology 3 (,510650) (, ) Studies on the Xylem Draught - Tolerant Characteristics of Three Draught - Tolerant Tree Species. Shen Weijun, Peng Shaolin ( Southern China institute of Botany, CA S, Guangz hou ), Zhang Shuoxin ( Faculty of Resources, Northwestern Forest ry U niversity, Yangling, S haanxi ). Chinese Journal of Ecology,2000,19 (6) :1-6. The xylem embolism vulnerability and refilling ability were measured in one - year - old twigs of three draught - tolerant tree species, which were Ul m us pumila L., Hippophae rham noides L., and Corylus heterophylla Fisch., and three types of vulnerability curves for them were also estab2 lished. The results showed that the water potential threshold for inducing embolism in three species was MPa, and the embolism reached its maximum value at the water potential of MPa. The xylem embolism vulnerability of three species was in the order of Hippophae > Ul2 mus > Corylus. The refilling of embolized xylem could occur while the water potential is below zero in all the species. In Hippophae, fully restoring occurred after thirty minutes under the water poten2 tial of - 015MPa and - 110MPa, but for Ulmus and Corylus, the restoration could reach about 90 % in thirty minutes under the water potential of MPa and MPa, respectively. Ul2 mus could restore fully through one night (12hours) under the water potential of MPa. The refilling capacity of three species was Hippophae > Ul m us > Corylus. The xylem of the three draught - tolerant species is not only very vulnerable to embolization or very sensible to water stress but also capable of refilling its embolized xylem in a short period of time. Vulnerable and drought - tolerant species had significant xylem embolism in higher water potential, which decreased the hy2 draulic conductivity so that limited water loss. Drought - tolerant species had more ability to refill its embolized xylem in a short period of time. These were the ways through which trees resist and toler2 ate drought or water stress. Key words :draught - tolerant tree species, xylem embolism vulnerability, refilling ability, draught - tolerant characteristics.,,,,,,, 3 ( ), ( ). :,,28,, 1997,, 15

2 2 19 6, [1,2 ], ,,,,, 1,,,,,, J m - 2,2105h, 1219, ( 7 ) 2518, (1 ) - 111, 42, , , 309d, , 206d, 221d,651mm, (4 9 ) 79 % 1) [ 3 ], ( Ul m us pum ila L. ), ( Hippophae rham noi des L. ) A : ( Coryl us heterophylla Fisch) 210MPa 10 13, 2 30min,, 5,,, 2. 2,,, [3 ], 6 10cm, 1412mmol L m, (4 ), 2 3, 20min,, L HC ( %) = HC max - HC min HC max 100 % HC min (mg MPa - 1 min - 1 ), HC max, L HC ( %) , 1)

3 : 3, B : 210MPa 30min, ( < 013MPa min - 1 ), 0Mpa, 10 30min,, ( %) = 1 - L HC t 100 % 1 - L HC c ( %) = (1-100 % W P t - W P c W P c ), L HC t, L HC c ; W P t, W P c x ( M Pa), y,3 3 VC ( 1), y x R S F,, 2,, lim X - y = a, ( - b/ 2, a/ e 2 ), - b/ 2 x 0, y x,, 0 = - b/ 2 ;, lim X - y = 1 b ( 1),3 > > 3 14 ( ) 1 3 VC Tab. 1 VC models of three tree species and test precision (n) R S F y = / x y = e x x 2 y = x y = / x y = e x x 2 y = x y = / x y = e x y = x : 0, L HCmax. x 2 F F (1, n - 2) F (1,22) = F (1,26) = F (1,21) = = MPa L HCmax = % 0 = MPa L HCmax = % 0 = MPa L HCmax = %

4 VC Fig. 1 The optimum VC of three tree species 1, VC,, y x ;, y x, < < () 5, ,3,A, ( MPa) ( MPa), ( 2),5146, 210MPa 30min 2, (),, 2 3 Tab. 2 Refilling of embolized xylem in three draught - resistant tree species WP(MPa) L HC( %) WP(MPa) L HC( %) ( %) min MPa min MPa min MPa min MPa (12h) :WP ;L HC ; HC ( %). 3 ( - 015MP) ( - 110MPa) 10min 30min, 30min (100 %, ),3 WP HC,,,,,,3 30min 10min,,,

5 : 5 10min 30min, 10min,, > > ; 30min, > >,,3,3 > >,3 4,, [5 ], [6,7 ] 3,, [8 11 ], 3, MPa ; MPa,,,, Cochard Breda 4 () [12 ], 3-215MPa, Q uer2 cus rubra L., - 115MPa,, 3-110MPa ; - 210MPa, 100 % [13 15 ] ( ) ( [7,16 ], Cochard [15 ] 7, MPa ; ( Pi nus tabulae2 f orm is) ( Picea asperata), - 215MPa,, [17,18 ], [19,20 ], [21 ], - 015MPa - 110MPa,30min ; MPa MPa, 90 %, MPa, (4 7 9 ) [3 ],3,,,,,,,,,,,,,,, ),,

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