摘 要 ：以苹果园内2年生紫花苜蓿为材料，设0.150、0.225（正常水平） 和0.300 m 3/m 2共3个灌溉量处理，研究不同灌溉量对紫花苜蓿生物量、光合生理指标、叶绿素含量、脯氨酸含量及电导率的影响。结果显示：（1）灌溉量对紫花苜蓿地上生物量有显著的影响，且随灌溉量的增加而增加；灌溉量大的处理苜蓿吸收根分布有浅层化趋势。（2）不同灌溉量处理的紫花苜蓿叶片净光合速率(Pn)与光合有效辐射(PAR)的变化趋势基本一致，均表现为在低PAR时Pn迅速增加，达到一定PAR后，Pn增幅渐趋平缓；净光合速率均随灌水量的增加而增加。（3）灌溉后土壤含水率和苜蓿叶片叶绿素含量随灌溉量的增加而升高，苜蓿叶片相对电导率随着灌水量的增加而呈现降低的趋势，低灌溉量可导致紫花苜蓿叶片中脯氨酸含量大量积累。研究表明，适当的灌溉可以有效改善苹果园土壤水分状况，提高紫花苜蓿光合生产力。
Abstract:With 2 years alfalfa (Medicago sativa) grown under apple trees as material,0.150,0.225 （control） and 0.300 m 3/m 2,three water amount levels were set up.The effects of different irrigation grads on biomass,photosynthetic parameters,chlorophyll content,proline content and relative electric conductivity of alfalfa were studied.Our results showed that:(1)Soil moisture content and above-ground biomass of alfalfa was significantly affected by the irrigation,and it increased with the increasing irrigation amount.Under high irrigation amount treatment the roots tended to distribute in surface layer.(2)Net photosynthetic rate (Pn) of alfalfa increased with the increase of photosynthetic active radiation (PAR) under all irrigation treatments.It increased rapidly under lower PAR value,and ascended smoothly when PAR reached certain value.Pn increased with increase of irrigation amount.(3)Chlorophyll content in leaves of alfalfa increased after irrigation.Relative electric conductivity in leaves of alfalfa decreased with the increase of irrigation amount.Proline accumulated significantly under lower irrigation amount,indicating that it may play an important role in drought resistant.Irrigation can effectively improve the soil water condition and increase photosynthetic productivity of alfalfa.