CHANGE IN LEAF ANATOMY, TOTAL CHLOROPHYLL CONTENT, AND CANOPY REFLECTANCE OF FIELD GROWN RICE AS A FUNCTION OF NITROGEN STATUS

摘要

Experiments were conducted to examine leaf anatomical characteristics, total chlorophyll concentration (TCC), and canopy reflectance behavior as a function of nitrogen (N) status in field grown rice cultivar Tainung 67. Results showed that applying different rates of N fertilizer, from 0 to 180 kg N ha-1 with 60 kg N ha-1 intervals, changed plant N status and leaf TCC measured in the panicle initiation/formation stage. Reflectance of waveband regions in visible light negatively corresponded to leaf TCC. A diversity of anatomical features was also observed in leaves from tagged plants of varied N status grown in both first and second crops. Leaf thickness increased progressively with increasing aboveground N concentration (ANC). Leaf rolling extent was relieved by the increasing ANC so that a higher value of leaf rolling index (LRI) was computed, i.e., LRI changed positively with the ANC in a linear fashion. Changes in ratio of bulliform/mesophyll to ANC were best fitted to a quadratic function, implying stronger leaf movement strength occurred in plants with higher N. In the measured range of ANC, leaf water content (LWC) also changed in a curvilinear trend and was low in plants of lower level N. Of the same ANC, plants grown in first crop had higher LWC than those plants grown in second crop. Starch granules were shown loosely distributed and packed in the parenchyma cells of mesophyll in plants of higher ANC relative to those of lower ANC ones. Different application rates of N fertilizer also affected canopy reflectance behavior. The mean reflectance of blue, green, and red regions decreased while near-infrared region increased with the increasing ANC and LRI.