Veneklaas Erik, VAN DEN Boogaard Riki
Department of Plant Ecology and Evolutionary Biology, Utrecht University, PO Box 800.84, 3508 TB Utrecht, The Netherlands.
International Center for Agricultural Research in the Dry Areas, PO Box 5466, Aleppo, Syria.
New Phytol. 1994 Oct;128(2):331-337. doi: 10.1111/j.1469-8137.1994.tb04017.x.
The wheat cultivars 'Katya Al' and 'Mexipak 65', grown in pots under field conditions in a Mediterranean climate, differed only slightly in growth and water use on a whole-plant basis, although Mexipak had a smaller leaf area. When expressed on a leaf area basis, plant biomass increase and transpiration were significantly greater in Mexipak. However, previous gas exchange measurements on the youngest fully expanded leaf showed only minor differences between the two cultivars. The hypothesis that different patterns of leaf ageing contributed to the differences in plant growth and water use was tested by combining leaf demography and gas exchange measurements. Plants were subjected to two moisture treatments: 'well-watered' (frequent, watering to initial soil water content) and 'intermittent drought' (five drying-rewatering cycles). Mexipak had, on average, older leaves than Katya in both treatments because of fast early growth, which in turn was clue to a larger area of individual leaves rather than a faster leaf appearance rate. Stomatal conductance and net photosynthetic rate were nearly the same for the two cultivars, but were considerably reduced by drought and did not fully recover after rewatering. Stomatal conductance and photosynthesis tended to decrease with ape, but effects of age or treatment or their interactions were not significant and could not explain the discrepancy between whole plant and leaf observations. One possible explanation is that age effects-do exist in leaves older than those investigated. Another explanation may be that changes in microclimatological conditions caused photosynthesis and transpiration to differ from rates measured under standard conditions.
在盆栽条件下于地中海气候的田间种植的小麦品种“Katya Al”和“Mexipak 65”，尽管Mexipak的叶面积较小，但在整株植物的生长和水分利用方面仅略有差异。以叶面积为基础表示时，Mexipak的植物生物量增加和蒸腾作用显著更大。然而，之前对最年轻的完全展开叶进行的气体交换测量表明，两个品种之间只有微小差异。通过结合叶片统计和气体交换测量，对不同的叶片衰老模式导致植物生长和水分利用差异的假说进行了检验。对植株进行两种水分处理：“充分浇水”（频繁浇水至初始土壤含水量）和“间歇性干旱”（五个干旱-复水周期）。在两种处理中，由于早期生长迅速，Mexipak的叶片平均比Katya的叶片更老，而早期生长迅速又是由于单叶面积较大而非叶片出现速率更快所致。两个品种的气孔导度和净光合速率几乎相同，但干旱使其大幅降低，复水后也未完全恢复。气孔导度和光合作用倾向于随年龄下降，但年龄、处理或它们的相互作用的影响不显著，无法解释整株植物和叶片观测结果之间的差异。一种可能的解释是，年龄效应确实存在于比所研究叶片更老的叶片中。另一种解释可能是，微气候条件的变化导致光合作用和蒸腾作用与在标准条件下测得的速率不同。
