白菜型冬油菜叶片结构和光合特性对冬前低温的响应

为明确白菜型冬油菜在冬前低温下叶片结构特征、光合作用特性及其抗寒性,本研究在0℃和–7.6℃自然低温条件下,选用白菜型冬油菜品种陇油7号(超强抗寒)和天油4号(弱抗寒),测定并比较其叶片气孔性状、解剖结构和光合、荧光参数的日变化等指标。结果表明,随着冬前温度下降,2个白菜型冬油菜叶片气孔密度、气孔面积、气孔周长、栅栏组织和海绵组织厚度均变小,细胞间隙变大,叶片变薄;P_n日变化呈"单峰"型曲线,无光合"午休"现象;叶片的P_n、G_s、T_r和CE均降低,而C_i均升高,说明是非气孔限制引起P_n降低。白菜型冬油菜在冬前低温条件下发生了光抑制现象,表现为F_m和F_v/F_m下降,F_o上升。与超强抗寒品种陇油7号相比,弱抗寒品种天油4号叶片气孔密度和气孔面积均较大,气孔总周长较长,叶片较厚,P_n、F_m和F_v/F_m均较高,说明冬前低温条件下,天油4号光合能力较强,光抑制程度较弱。白菜型冬油菜在冬前低温条件下的叶片气孔密度越大、气孔面积越大、气孔周长越长、叶片及栅栏组织和海绵组织越厚,光合能力越强,地上部生长越旺盛,品种抗寒性越差。本研究为冬油菜抗寒种质创新和育种提供了部分理论支撑。

Response of Leaf Anatomical Structure and Photosynthetic Characteristics of Winter Turnip Rape (B. rapa L.) to Low Temperature before Winter

Stomatal traits, leaf anatomic structure characteristic and diurnal variation of photosynthesis and fluorescence parameters, in two winter turnip rape (B. rapa L.) cultivars Longyou 7 (strong cold-tolerant) and Tianyou 4 (weak cold- tolerant) were determined under 0°C and –7.6°C natural low temperature conditions to clear the effects of low temperature on leaf anatomical structure, mechanism of photosynthesis and cold resistance. With decreasing the temperature before winter, stomatal density, stomatal area and total stomatal circumference per unit area in two cultivars decreased. Moreover, leaf thickness, palisade tissue and sponge tissue thickness became thinner and cellular space grew bigger. The diurnal variation of net photosynthetic rate of two cultivars presented a single-peak curve, and no typical mid-day depression occurred. Under the lower temperature, P_ndeclined with a non-stomatal limitation in two cultivars. Photo inhibition in the two cultivars occurred under low temperature and increased with the temperature decreased. Compared with Longyou 7, Tianyou 4 had bigger stomatal density, stomatal area, total stomatal circumference per unit area and leaf thickness, as well as higher photosyntheticcapacity and weaker photo inhibition. In conclusion, higher photosynthesis and faster growth in winter turnip rape under lower temperature may result from its bigger stomatal density, stomatal area and total stomatal circumference per unit area as well as thicker leaf, palisade tissue and sponge tissue, which results in a poorer resistance to cold stress. The result may be useful for mining new germplasm and facilitating winter turnip rape breeding for cold resistance.