干旱胁迫对不同土壤基质下核桃楸幼苗的生理特性的影响

为探究不同土壤基质条件下核桃楸幼苗对干旱胁迫生理特性的响应,以两年生核桃楸幼苗为研究对象,在腐殖土、壤土和砂壤土三种基质条件下进行控水试验,水分梯度分别设置为CK(正常供水,80%田间持水量)、T1(轻度胁迫,60%田间持水量)、T2(中度胁迫,40%田间持水量)和T3(重度胁迫,20%田间持水量),测定幼苗叶片叶绿素、丙二醛、脯氨酸、抗氧化酶和光合指标。结果表明,随着胁迫程度的加深,叶绿素含量和Chla/b均呈逐渐降低的趋势(P<0.05),在胁迫60d时,T3处理下的叶绿素a(Chla)和叶绿素b(Chlb)分别比CK低65.41%和51.57%,3种基质中叶绿含量大小顺序为:腐殖土>壤土>砂壤土。随着胁迫程度的加深,叶片脯氨酸(Pro)、丙二醛(MDA)则呈逐渐升高的趋势(P<0.05),胁迫60d时,砂壤土中T3处理的Pro含量最高为83.37mg·g-1,比CK高86.32%。腐殖土中幼苗叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性均随胁迫程度加深而升高,壤土中叶片SOD活性则呈先升高后降低的变化规律。3种土壤基质中核桃楸叶片净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)均随着胁迫程度的加深而降低,但不同基质中幼苗叶片的气孔限制和非气孔限制发生的时间不同,T3处理的叶片胞间CO2浓度(Ci)在腐殖土中是12:00时最低,而在壤土和砂壤土中则是10:00时最低。土壤全氮、全磷、渗透速率和蒸腾速率与叶绿素含量存在显著的正相关关系(P<0.05),土壤容重与叶绿素含量存在显著的负相关关系(P<0.05)。因此,土壤基质和干旱胁迫对核桃楸幼苗的生理生化和光合特性产生了显著的影响,重度胁迫对幼苗的叶绿素、渗透物质和酶体系产生了严重的损伤,同时降低了核桃楸幼苗的光合生产力。总体上,腐殖土中的幼苗有着较好的抗旱表现。

Effects of Drought Stress on Photosynthetic and Physiological Characteristics of Juglans mandshurica Seedlings in Different Soil Substrates

To investigate the response of photosynthetic physiological characteristics in seedlings of Juglans mandshurica under water stress in different soil substrates, In this study, two-year seedlings of J.mandshurica were used as research objects, and an experiment was conducted to set four water gradients(normal water supply CK, mild stress T1, moderate stress T2 and severe stress T3, and 80%, 60%, 40%, 20% field water capacity, respectively) in three soil substrates(humus, loam, sandy-loam) by pot controlled water method respectively. The chlorophyll, malondialdehyde(MDA), proline(Pro), antioxidant enzymes(POD, SOD, CAT)and photosynthesis indicators were determined in all treatments. The results showed that the chlorophyll content and Chl a/b were significantly decreased with increase of stress intensity(P<0.05). After 60 d of persistent water stress, the Chl a and Chl b content were 65.41% and 51.57% lower than those of CK, respectively. The order of chlorophyll content in the three matrices was:humus>loam>sandy-loam. With the increase of stress intensity, the proline(Pro) and malondialdehyde(MDA) content of seedlings were significantly increased, and Pro content in T3 in sandy-loam soil was 83.37 mg·g^-1, which was highest among all treatment, and was 86.32% higher than CK. The activities of superoxide dismutase(SOD), peroxidase(POD) and catalase(CAT) of seedlings significantly increased with increase of stress intensity in humus soil. However, the SOD activity in loam soil increased first and then decreased. In general, the net photosynthetic rate(P_n), transpiration rate(T_r) and stomatal conductance(G_s) of seedlings decreased with increase of the stress intensity in three soil substrates. However, the stomatal limitation and non-stomatal limitation of seedling leaves in different soil substrates were different. The intercellular CO₂ concentration(C_i) of T3 treated leaves was lowest in humus at 12:00, while in loam and sandy loam were 10:00. There was a significant positive correlation between soil total nitrogen, total phosphorus, permeation rate and transpiration rate and chlorophyll content(P<0.05), and reach a significant negative correlation between soil bulk density and chlorophyll content(P<0.05). Soil substrate and water stress had significant effects on the physiological characteristics and photosynthesis of J.mandshurica seedlings. Severe stress caused serious damage to the chlorophyll, osmotic substances and enzyme system of seedlings, and decreased the photosynthetic productivity of J.mandshurica seedlings. The seedlings in humus and loam have better drought resistance.