Manipulating phenology and water relations in Senna spectabilis in a water limited environment in Kenya

Abstract

The effect of shoot pruning on leaf phenology, stem wood anatomy and sap flow was investigated on Senna spectabilis (DC.) Irwin and Barneby in Machakos, Kenya. Unpruned trees (single stem) were compared to hedges (two to four stems), pruned 4 times a year during two rainy seasons (AprilJune, 1997 and November, 1997-January, 1998 separated by a dry season (July-October 1997). Trees attained peak leaf area of 55 m 2 plant -1 during the rainy seasons, and shed all their leaves naturally during the dry season. Maximum hedge leaf area was 4 m 2 plant -1 between pruning events and 5.2 m 2 plant -1 during the dry season. Pruning induced multiple stems and narrow xylem vessels with low hydraulic conductivity. Average cross sectional area of conducting wood per plant was at least 1.8 times greater in trees than in hedges. Xylem lumen diameter at 5 mm depth below the cambium was significantly (P \ 0.001) larger in trees (53.6 ± 6.21 lm) than that in hedges (36.2 ± 8.21 lm). Maximum sap flow occurred in the wet season for trees (4800 g d -1 plant -1 ) and in the dry season for hedges (1400 g d -1 plant -1 ). Wet season pruning suppressed crown expansion and modified the natural phenology of senna, reducing transpiration rate and therefore soil water depletion, causing crowns to grow. This enhanced the ecological combining ability of senna managed as hedges with annual crops.

Effects of water stress on growth, dry matter allocation and water-use efficiency of a leguminous species, Sophora davidii

“…2c and 2d), as there was no leaf shedding. Reduced leaf area results in reduced transpiration surface (Ares and Fownes 1999;Namirembe et al 2008), and may be a drought avoidance strategy for the plants. On the other hand, the reduction of leaf area limits photosynthesis, and further decreases biomass production, consistent with the positive correlation between total leaf area and biomass production (Fig.…”

“…Water deficit is often a key factor limiting plant growth, productivity and survival (Boyer 1982;Puri and Swamy 2001;Sánchez-Coronado et al 2007;Namirembe et al 2008), and often adversely affects agroforestry practices in arid and semi-arid areas. Plants can normally acclimate to water stress through physiological and morphological responses (Brouwer 1963;Puri and Swamy 2001;Coopman et al 2008).…”

Growth, biomass allocation, and water use efficiency of 31 apple cultivars grown under two water regimes

“…Adaptations are achieved by modifying leaf anatomical structures (Fang et al 2000) and photosynthetic characteristics. Here, drought induced decreases in TLA, LAR, A, T r , and g s , resulting in diminished biomass accumulation and relative growth but greater WUE, and d 13 C. This reduction in TLA is considered a dehydration-avoidance mechanism that minimizes water loss by shrinking the amount of leaf surface available for transpiration (Ares and Fownes 1999;Namirembe et al 2009). Such a morphological change enables Table 4 Linear correlations (Pearson's coefficients) among total fresh biomass (TB), total dry biomass (TDB), root: shoot ratio (RSR), relative growth rate (RGR), total leaf area (TLA), specific leaf area (SLA), relative water content (RWC), waterholding capacity (WHC), net photosynthesis (A), stomatal conductance (g s ), long-term water use efficiency (WUE L ), instantaneous water use efficiency (WUE I ), and carbon isotope composition (d 13 C) of 31 apple cultivars under well-watered (control) or drought conditions Agroforest Syst (2012) 84:117-129 125 plants to withstand long periods of water deficit while maintaining their photosynthetic activity (Dichio et al 2002;Maggio et al 2005).…”

Agroforestry: Hydrological Impacts

“…Pruning offers a direct and adaptable method of controlling competition and has been the focus of several studies in East Africa (Tefera, 2003;Rao et al, 2004;Wajja-Musukwe et al, 2008;Namirembe et al, 2009;Siriri et al, 2010Siriri et al, , 2012. This practice enables farmers to grow the tree species they prefer by managing their growth.…”