间伐改形对陇东高原密闭富士苹果园冠层微域环境及叶片生理特性的影响

Effects of thinning and reshaping on canopy micro-domain environment and leaf physiological characteristics in dense Fuji apple orchard on Loess Plateau of eastern Gansu, China

为了研究间伐改形对成龄乔化密闭红富士苹果园冠层微域环境、叶片显微结构、叶片生理特性和光合能力的影响,以16年生密闭红富士苹果园为研究对象,对果园冠层相对光照强度、温度、相对湿度、叶片叶绿素含量、显微结构、叶片光合和荧光等参数进行了测定。结果表明:间伐改形后树体冠层相对光照强度、温度得到显著改善,分布更均衡,>30%的有效光强是对照(未间伐改形,CK)的1.57倍,温度比CK平均高1.1℃;间伐树体叶片叶绿素、叶片厚度、栅栏组织厚度显著提高,分别比CK提高了8.7%、5.4%、9.2%;叶片净光合速率、蒸腾速率、气孔导度也显著提高,分别比CK提高了12.6%、17.1%和7.3%。间伐果园和密闭果园叶片光合作用均受非气孔因素限制,间伐树体叶片的PSⅡ最大荧光产量和非光化学猝灭系数比CK提高了1.5%和2.1%。间伐改形后,叶片并未发生强光抑制,叶片单位反应中心吸收的光能、捕获的用于电子传递的能量和用于还原Q_A的能量得到显著提高。叶片生理特性与所处的光照、温度环境密切相关,密闭果园间伐改形后,果园冠层光照、温度得到改善,促进了叶片生长发育,改善了叶片显微结构,提高了叶片光合效能,是适宜陇东高原苹果产区密闭红富士果园调整和优化的关键措施。

We examined the effects of thinning and reshaping on the canopy micro-domain environment, leaves micro-structure, physiological characteristics and photosynthetic capacity of 16 year-old Fuji apple dense orchards by measuring canopy relative light intensity, temperature, relative humidity, leaf chlorophyll content, micro-structure, and photosynthetic fluorescence. After thinning and reshaping, relative light intensity and temperature of tree canopy were significantly improved, and the distribution was balanced. Effective light intensity(>30%) was 57% higher than that of control(thinning and reshaping, CK), and temperature increased by 1.1 ℃. Due to the improvement of relative light intensity and temperature in the canopy, leaf chlorophyll, leaf thickness, and palisade tissue thickness of thinning trees were increased by 8.7%, 5.4%, and 9.2%, respectively. Net photosynthetic rate, transpiration rate and stomatal conductance of the leaves were also significantly increased, being 12.6%, 17.1% and 7.3% higher than CK, respectively. Leaf photosynthesis capacity of both treatments was limited by non-stomatal factors. After thinning and reshaping, F_m(maximum fluorescence) and q_N(non-photochemical quenching coefficient) of PSⅡ in leaves were increased by 1.5% and 2.1%. Leaves did not suffer strong light photoinhibition, with ABS/RC(unit reaction center absorbs light energy), ETo/RC(energy used for electron transfer captured by unit reaction center) and TRo/RC(energy captured by the unit reaction center to reduce Q_A) of leaves being significantly improved. The physiological characteristics of leaves were closely related to light and temperature environment. After thinning, light and temperature of the orchard canopy were improved, which promoted leaves growth and development, improved foliar micro-structure and photosynthetic efficiency. Thinning and reshaping were suitable strategies for the adjustment and optimization of Fuji orchard density in Loess Plateau of eastern Gansu.