Leaf development in Ricinus communis during drought stress: dynamics of growth processes, of cellular structure and of sink–source transition

Abstract

Dicot leaf growth is characterized by partly transient tip-to-base gradients of growth processes, structure and function. These gradients develop dynamically and interact with dynamically developing stress conditions like drought. In Ricinus communis plants growing under well-watered and drought conditions growth rates peaked during the late night and minimal values occurred in the late afternoon. During this diurnal course the leaf base always showed much higher rates than the leaf tip. The amplitude of this diurnal course decreased when leaves approached maturity and during drought stress without any significant alteration of the diurnal pattern and it increased during the first days after rewatering. Unique relationships between leaf size and cytological structure were observed. This provided the framework for the analysis of changes in assimilation, transpiration and dark respiration, chlorophyll, protein, carbohydrate, and amino acid concentrations, and of activities of sink-source-related enzymes at the leaf tip and base during leaf development in well-watered and drought-stressed plants. Gas exchange was dominated by physiological rather than by anatomical properties (stomatal density). Tip-to-base gradients in carbohydrate concentrations per dry weight and sink-source-related enzymes were absent, whereas significant gradients were found in amino acid concentrations per dry weight. During drought stress, growing leaves developed source function at smaller leaf size, before specific physiological adaptations to drought occurred. The relevance of the developmental status of individual leaves for the drought-stress response and of the structural changes for the biochemical composition changes is discussed.

Interactions between drought and shade on growth and physiological traits in two Populus cathayana populations

“…It may have also been related to the increased leaf thickness and decreased leaf RWC induced by drought. The increased chlorophyll content under environmental stress has also been detected in some previous experiments (Schurr et al 2000;Renaut et al 2005). Additionally, we observed that shade increased the Chla and Chlb content in both populations.…”

Root Morphology, Plant Growth, Nitrate Accumulation and Nitrogen Metabolism of Temperate Lettuce Grown in the Tropics with Elevated Root-Zone CO<sub>2</sub> at Different Root-Zone Temperatures

“…However, in this study, regardless of RZ [CO 2 ] treatments, there were no differences in average root diameter at either 20˚C-RZT or A-RZT (Figure 1(D)). The temperature of a sink could affect its metabolic rate and thus its capacity to utilize carbohydrate [27]- [29]. Elevated RZ [CO 2 ] could also affect the physiological activities of roots and thus alter the pattern of photoassimilate partitioning.…”

Lâminas De Irrigação E Coberturas Do Solo Na Cultura Do Girassol, Sob Condições Semiáridas

“…Os menores valores de altura de plantas e de diâmetro do caule nas condições mostradas nesse estudo sob baixos níveis de irrigação, provavelmente, ocorreram devido o fato do déficit hídrico provocar o fechamento dos estômatos, diminuindo a assimilação de CO 2 e, conseqüentemente, diminuindo as atividades fisiológicas das plantas, principalmente a divisão e o crescimento das células, refletindo assim em uma menor produtividade. Comentário semelhante fizeram Schurr et al (2000) e Rego et al (2004). Para a massa de 1000 aquênios (Figura 3) verificaram-se aumentos lineares em função do aumento das lâminas aplicadas, com efeito significativo (p < 0,05) e coeficientes de determinação de 0,977.…”