水分胁迫对夏玉米胞间CO2浓度、维管束鞘细胞CO2泄漏和叶片碳稳定同位素的影响

通过盆栽试验,采用碳稳定同位素技术和LI-6400便携式光合仪分析探讨了不同水分条件对夏玉米各典型生育期胞间CO2浓度(Ci)、维管束鞘CO2泄漏率(φ)和叶片碳稳定同位素判别值(Δ13C)的影响,并研究了它们之间的关系。试验设四个水分条件:分别为田间持水量的75%~100%(W1),50%~75%(W2),30%~50%(W3),0~30%(W4)。结果表明:(1)夏玉米拔节期水分胁迫时气孔关闭导致了Ci降低。在孕穗、抽雄和灌浆期,W1、W2和W3处理下Ci依次降低。W4处理由于严重干旱而导致Ci大于W2和W3处理;成熟期叶片的老化导致了Ci在成熟期随着水分胁迫的增加而增加;(2)叶片Δ13C和Ci/Ca的关系受水分条件和生育期双重影响,从拔节到灌浆,叶片Δ13C在W1、W2和W3三种处理中的变化趋势与Ci/Ca一致,而成熟期则不一致;W4处理的叶片Δ13C从孕穗到灌浆的变化趋势与Ci/Ca一致,其余生长期不一致。而在各水分处理下,叶片Δ13C与φ均呈极显著正相关,且φ对叶片Δ13C的影响均大于Ci/Ca;(3)在不同水分处理中,φ的变化和叶片Δ13C的变化一致。W1、W2和W3处理下,φ随着水分胁迫的增加而降低,但严重水分胁迫会增加φ。

INTERCELLULAR CO_2 CONCENTRATION,CO_2 LEAKAGE FROM BUNDLE SHEATH CELL AND STABLE CARBON ISOTOPE IN LEAF OF SUMMERMAIZE UNDER WATER STRESS

A pot experiment of maize was conducted from June 9 to September 25 in 2007, to explore variations and relationships between intercellular CO_2 concentration (C_i), stable carbon isotope discrimination (Δ~(13)C) and CO_2 leakage from bundle sheath (φ) during photosynthesis of summer maize in six typical growth stages (seedling, jointing, booting, tasseling, filling, and mature) under different water regimes, using the stable carbon isotope technique and Portable Photosynthesis System (LI 6400, LI COR, Inc., USA). The plants were subjected to four water regimes, i.e. 75% ～100% (Treatment W1), 50% ～75% (Treatment W2), 30% ～50% (Treatment W3) and 0～30% (Treatment W4) of the field capacity of the soil. Results show that (1) stomas on the summer maize leaf closed under water stress at the jointing stage, which led to lower C_i in Treatments W2, W3 and W4, as compared with that in Treatment W1. At the following growth stages of booting, tasseling and filling, C_i in Treatments W1, W2 and W3 decreased with intensifying water stress; however, C_i in Treatment W4 was higher than in Treatments W2 and W3. Leaf aging sped up and C_i increased with intensifying water stress at the maturing stage; (2) under the joint effect of water regimes and growth stages, in Treatments W1, W2 and W3 Δ~(13)C for summer maize leaves displayed a trend similar to that of C_i/C_a from the jointing stage to the filling stage, but a different one at the maturing stage; whereas in Treatment W4 it did only from the booting stage to the filling stage; no matter in what treatments, Δ~(13)C was significantly correlated with φ, which affected Δ~(13)C more than C_i/C_a did; and (3) φ varied in a trend similar to that of Δ~(13)C in the maize leaf in all the treatments, however, in Treatments W1, W2 and W3 φ declined with intensifying water stress, while in Treatment W4 it turned upwards.