Water Relations and Productivity of Alfalfa Leaf Chlorophyll Variants

Abstract

Plant improvement to increase the water‐use efficiency of affalfa (Medicago sativa L.) has been limited. This study compared leaf color variants (pale and dark) to evaluate the effect of alfalfa leaf chlorophyll on water relations and yield of alfalfa. Leaf color populations were selected from ‘Ladak 65’ and visually selected sub‐populations evaluated under controlled‐environment and field conditions. Seven moisture regimes were established in controlled environment studies in which a commercial root medium with high water‐holding capacity was used. The field study was at Laramie, WY, on a Wyocolo soil (fine, loamy, mixed Borollic Haplargid) and consisted of irrigated and nonirrigated treatments. Traits measured for the two populations included leaf chlorophyll (Chl), leaf photo‐synthesis (as CO2 exchange rate: CER), transpiration (T), stem pressure potential (ψw), water‐use efficiency (WUE), leaf area, forage yield. Controlled. environment conditions produced pale plants that contained 15% less total Chl than dark‐leaved variants. The Chl concentration of pale variants was equal between the moisture extremes, while the dark variants decreased 20% for the low‐moisture (compared with high moisture) regime in the controlled environment. The WUE in the controlled environment of pale and dark leaf types averaged 1.47 and 1.22 g dry forage kg−1 water, respectively. This difference in WUE was attributed mostly to the greater growth of pale leaf types. The CER and CER/T ratio of the dark leaf types were more sensitive to moisture stress than the pale types. In the 2‐yr field study, the pale leaf types had a 22% lower CER than the dark leaf types across moisture regimes and 19% lower T under the irrigated regime. Even though leaf photosynthesis was lower for the pale leaf types, the forage yield was 25% higher under the irrigated regime.

Variation in thylakoid proteins and photosynthesis in Syrian landraces of barley

“…The temperature difference exhibited between pale-and normal-green barley was believed to have been mainly the result of increased reflectivity of light from the leaf surface . The lower temperature of pale leaves may also result in significantly lower transpiration rates and, where photosynthetic rates are maintained, greater water use efficient (WUE) (Fisher, 1981 ;Estill et al ., 1991) . The light green genotypes we have studied may also have a similarly high albedo thus minimising the amount of light energy absorbed and reducing leaf temperature.…”

Photosynthetic response of the floating-leaved macrophyteNymphoides peltatato a temporary terrestrial habitat and its implications for ecological recovery of Lakeside zones

“…By regulating these physiological activities, N. peltata could maintain its water balance and photosynthesis (Estill et al, 1991;Luquez et al, 1997). Thus, N peltata growing under terrestrial conditions could acclimate to temporarily stressed environments.…”

Studies on endogenous hormonal changes during grain development in wheat genotypes

“…This shows that there was more chlorophyll content at rapid grain growth stage, during which there is a great demand for photosynthates and this might help the plant to fix more co2 and meet the increasing demand for photosynthates. Wright and Smith (1983), Ashraf and Khan (1990), Sinha and Patil (1986) and Estill et al (1991) reported a wide variation in chlorophyll contents within species. In the present investigation also the genotypes differed significantly in chlorophyll content.…”