弱光胁迫影响甘蔗叶片内源激素的平衡和分蘖进程

Weak-light stress caused by shading affects the balance of endogenous hormones in leaves and tillering process in sugarcane(Saccharum officinarum)

光是甘蔗生长发育的重要环境因子,充足的光照是甘蔗生育期中分蘖形成和生长的基础。然而,广西特殊的地形地貌限制了蔗田的光照条件,从而影响甘蔗分蘖及分蘖成茎和蔗茎产量。为揭示弱光胁迫对甘蔗分蘖生长发育及其内源激素含量的影响,以生态适应性较好的甘蔗优良品种‘桂糖29号’为试验材料,全自然光强为对照,通过遮荫形成不同的弱光胁迫,调查不同弱光胁迫下甘蔗分蘖及生长情况,同时分析胁迫15、30、45、60 d时甘蔗叶片中叶绿素含量及生长素吲哚乙酸(IAA)、赤霉素(GA_3)、脱落酸(ABA)、玉米素核苷(ZR)含量的变化。结果表明:弱光胁迫致使甘蔗分蘖生长发育明显延滞,甘蔗分蘖发生时间至少滞后15 d,严重的导致分蘖不发生和死亡;甘蔗叶片叶绿素含量均显著升高,但株高生长和茎径增粗均显著地受抑制,进而导致植株生物量积累显著减少。进一步研究发现,弱光胁迫下不同生育时期甘蔗叶片中内源激素含量大小为:ZR>IAA>ABA>GA_3。在适应弱光胁迫过程中,甘蔗叶片的IAA、ABA和ZR含量均显著升高,IAA/ABA、IAA/ZR比值在分蘖适应寡照胁迫中表现为升高;GA_3含量和GA_3/ABA比值均先降后升;ZR含量和ZR/ABA比值表现为升高。这些内源激素含量和比例变化可能是甘蔗分蘖进程受到抑制的关键因素之一。

Light is a very important environmental factor for the growth and development of sugarcane （Saccharum officinarum）, including sugarcane tillering. Sufficient light during the growing period is the basis of tiller formation and growth in sugarcane. However, light conditions in sugarcane field are always limited by topography and geomorphology in Guangxi province, furtherly influence sugarcane tillering, millable stalks from available tillers and cane yield in production. To determine the effects of tillering formation and growth under weak-light environment in sugarcane, as well as endogenous hormone content, S. officinarum cv. ＇GT29＇ seedlings were used to study the effects of different weak-light stresses on endogenous hormone contents in leaves and tillering process. The different weak-light stresses of 20.0%, 52.0% and 71.2% shading （respectively named as GS, GS1 and GS2） resulted from nylon nets （80.0% and 60.0% light transmittance） mulching from tillering stage to initial elongation stage. The results showed that the growth and development of sugarcane tillers were delayed under weak-light conditions, and the tillering process was postponed at least 15 days. The tillers did not produce or died during their growing under the weak light treatments （GS 1 and GS2）. The plant high, stalk diameter, fresh and dry weights of plants and tillering rate were significantly decreased while the total chlorophyll content was increased under different weak light conditions. Further study found that the content levels of hor- mones showed ZR〉IAA〉ABA〉GA3 in leaves. The contents of IAA, ABA and ZR and the ratios of IAA/ABA and IAA/ZR in leaves significantly increased while the GA3 content and the GAa/ABA ratio in leaves firstly de- creased and then increased under weak-light stress at tillering stage. The changes in hormone contents and ratios may be one of key factors for inhibiting the process oftillering in sugarcane.