Interactive Water and Nitrogen Effects on Senescence of Maize. II. Photosynthetic Decline and Longevity of Individual Leaves

Abstract

Stress‐induced senescence is frequently alluded to, but interactive effects of water and N deficits on leaf longevity and on physiological changes associated with leaf aging have received little attention. A 2‐yr field experiment with maize (Zea mays L.) was conducted on Yolo loam (fine‐silty, mixed, nonacid, thermic Typic Xerorthents) with four treatments: N fertilized (180 kg N/ha) with (NI) and without (ND) irrigation; and no N applied with (OI) and without (OD) irrigation. Size and longevity measurements were made of leaves at all nodal positions, and leaves 5, 11, and 15 (counting up from stem base) were monitored for changes in photosynthetic capacity (PC), N concentration, and chlorophyll content (CHL). Leaf PC was correlated with percent N during senescence in all treatments (r2 = 0.86), but an occasional midday depression in PC, unrelated to leaf N status, was observed in severely water stressed plants. Chlorophyll and percent N were also correlated (r2 = 0.80), but initial onsets of decline in these two parameters often differed by several days. Nitrogen deficits were less severe in 1983 than 1982, but in both years lack of applied N had an early impact and reduced longevity of lower leaves. In 1982, N deficiency caused a 50% reduction in leaf peak values of percent N, CHL, and PC, and the decline in leaf 5 was most rapid in low N plants. Water stress intensified as stored soil water was gradually depleted, and the most rapid decline and earliest complete senescence of upper leaves (11 and 15) occurred in the ND treatment. These results indicate that early stress effects on leaf area and ear development affected subsequent demands for water and N, which in turn altered patterns of leaf senescence.

Responsive in-season nitrogen management for cereals

“…Plants with increased levels of available N typically have greater leaf N concentrations, more chlorophyll (Inada, 1965;Al-Abbas et al, 1974;Wolfe et al, 1988), and greater rates of photosynthesis (Sinclair and Horie, 1989). Chlorophyll in leaves absorbs most strongly in the blue (around 450 nm) and red (around 670 nm) light, and reflects in the green (around 550 nm) region of the light spectrum.…”

Use of physiological parameters as fast tools to screen for drought tolerance in sugarcane

“…The degree of limitation of yield by environmental stresses varies even among genotypes within a species (Wolfe et al, 1988;Aguilera et al, 1999). Therefore, the ability to maintain key physiological processes, such as photosynthesis during moderate drought stress, is indicative of the potential to sustain productivity under water shortage.…”

Frequency distribution and mean comparisons of red light absorbance-transmittance of the e1 leaf sectors of five pipeline maize hybrids during early grain filling in subtropical winter

“…The e1 leaf is the central leaf that stays green longer than most of the top and bottom leaves which can be reflected from bidirectional plant senescence in the maize (Tollenaar and Daynard, 1978;Wolfe et al, 1988). Third important reason is that the ear (e0) leaf is badly damaged by the large size pointed ears of most of the promising hybrid of the maize.…”