α-NAA及UV-B辐射对栝楼幼苗生长及蒸腾作用的影响

EFFECTS OF a-NAA AND UV-B RADIATION ON THE GROWTH AND TRANSPIRATION OF TRICHOSANTHES KIRILOWII SEEDLING

研究了温室条件下紫外线-B(UV-B)辐射(0.029 J·m^(-2)·s^(-1))和外施a-萘乙酸(a-NAA)(2 mg·L^(-1))相互作用对栝楼(Trichosanthes kirilowii)幼苗生长及蒸腾速率的影响。本实验设一个对照(T_0)和3个处理:外施a-NAA(T_1),增加UV-B辐射(T_2),增加UV-B辐射并外施a-NAA(T_3)。实验结果:增强UV-B辐射明显降低栝楼的株高及叶面积,根、茎、叶重均较对照低,因而总生物量也较对照低,干物质积累量减少。UV-B辐射增强,对栝楼植株含水量几乎无影响,但却明显增加叶气孔阻力,降低蒸腾速率。与对照(T_0)相比,外施a-NAA(T_1)明显增加株高及叶面积,根、茎、叶重均增加,因而单株总生物量较对照增加,但干物质积累量增幅不大,植株水分含量较对照略高;叶气孔阻力呈降低趋势,蒸腾速率呈增大趋势。在有UV-B辐射下外施a-NAA(T_3),与T_2相比,植株高度、叶重及叶面积降低趋势明显减轻,但根、茎生物量,单株总生物量及干物质积累量并无明显增加;叶气孔阻力降低,蒸腾速率增大。分析认为,栝楼幼苗根系发达,根冠比接近1,而UV-B辐射下补充a-NAA对根、茎影响小,同时本试验处理时间短(5周),表现为对生物量增加及干物质积累量的影响效果不明显,但株高、叶面积明显增加,且在一定程度上减小了叶的气孔阻力,增大了蒸腾速率。

The depletion of the stratospheric ozone layer has been well documented. So ultraviolet-B (UV-B) radiation (280-320 nm) reaching the earth surface has increased since the 1970s. Although extensive studies were conducted about negative biological and ecological effects of enhanced UV-B radiation, little was known about the inside mechanism and effects of increased UV-B irradiation and feasible protective measures of plants. In this paper, the effects of naphthyl acetic acid (a-NAA) (2 mg·L-1) and UV-B radiation (0.029 J · m-2 · s-1 ) on the growth and transpiration rate in pots in greenhouse-grown Trichosanthes kirilowii seedlings were investigated. Four treatments were included in the experiment: no addition of a-NAA and UV-B radiation (T0) , addition of a-NAA (T1) , exposure to enhanced UV-B radiation (T2), addition of a-NAA and exposure to UV-B radiation (T3). The results showed that enhanced UV-B radiation reduced the height and leaf area of plants, and the weight of roots, stems and leaves. As a result, total biomass and accumulation of dry matter were decreased. Exposure to UV-B radiation significantly increased the stomatal diffuse resistance and decreased the transpiration rate; however it hardly affected the water content of seedlings. Compared to the controls (T0) , addition of a-NAA (Ti) significantly increased the plant height, leaf area, weights of roots, stems and leaves as well as total biomass, but only slightly increased the dry matter weight and water content. In the fourth treatment (T3 ) , the reductions of plant height, leaf weight and leaf area were smaller than those in the third treatment (T2) . Moreover, the weight of roots, stems, total biomass and accumulation of dry matter in T3 increased slightly. The analysis indicated that the seedlings have flourishing roots, RSR was nearly 1, and UV-B radiation scarcely affects roots. Since the experiment time period was short (five weeks), the effects on biomass and accumulation of dry matter when plants were given addition of a-NAA and exposed to UV-B (T3) were not significant. However, the addition of a-NAA apparently reduced the effects of UV-B radiation on plant height and leaf area. The experiment showed that interaction of UV-B and a-NAA can mitigate the negative effects of UV-B radiation on the biomass of roots, stems, leaves and accumulation of dry matter, and can also decrease stomatal resistance of plant leaves and increase transpiration rates. The result suggests that the a-NAA can strengthen the ability of plant seedlings to suffer enhanced UV-B radiation. It is possible that a-NAA makes up for the decreased content of IAA caused by UV-B radiation and reduces the content of endogenous ABA, which reduces the stomatal resistance of plant leaves and consequently increases transpiration rate of plant leaves, promoting plant growth.