Forage potential of Urochloa genotypes by using leaf anatomy

ABSTRACT: The digestibility potential of leaves from forages depends on the amount of nutrition in their tissues, with low lignin deposition in the cell wall, mainly parenchyma and phloem. This research evaluated the leaf structure of different Urochloa genotypes and discussed its potential for evaluating digestibility. The cultivars U. brizantha, U. decumbens, U. ruziziensis and three clones of U. ruziziensis (1, 95 and 97), which are under development in breeding programs, were evaluated. Plants were grown under the recommended culture conditions for the Urochloa species. Plants were cut 60 days after sowing, and leaves were collected at 15 days of regrowth. Leaves were fixed in FAA 70 and further stored in 70% ethanol until being submitted to the usual microtechniques for the preparation of microscopy slides. The area of the tissues from the interveinal and midrib regions was measured using ImageJ software, and their proportions were calculated. In the interveinal region, the proportion of chlorophyll parenchyma was greater for U. decumbens and the Clone 1 genotypes. Urochloa brizantha and clones 95 and 97 showed a higher proportion of the vascular bundle compared to U. ruziziensis, U. decumbens and Clone 1. The proportion of the ground parenchyma in the midrib was greater in U. brizantha, Clone 95 and Clone 97. Thus, it can be concluded that the Clone 1 genotypes (from U. ruziziensis) showed leaf tissues (parenchyma and phloem) with higher digestibility potential; in addition, U. brizantha and U. decumbens showed a high percentage of xylem and sclerenchyma, which reduces their quality as forage.

摘要：饲草叶片的消化潜力，取决于其组织的营养物质含量，以及细胞壁（以薄壁组织与韧皮部为主）的低木质素沉积水平。本研究评估了不同臂形草属（Urochloa）基因型的叶片结构，并探讨了其用于消化潜力评估的可行性。供试材料涵盖铺地臂形草（U. brizantha）、俯仰臂形草（U. decumbens）、鲁兹臂形草（U. ruziziensis），以及3个正处于育种研发阶段的鲁兹臂形草无性系（编号1、95、97）。所有供试植株均按照臂形草属物种的推荐栽培条件进行种植：播种60天后对植株进行刈割，待再生生长15天后采集叶片样本。采集的叶片经70% FAA固定液固定后，保存于70%乙醇溶液中，直至采用常规显微制片技术制备显微玻片。采用ImageJ软件测量脉间区与中脉区的组织面积，并计算各组织的占比。实验结果显示：在脉间区中，俯仰臂形草与无性系1的叶绿素薄壁组织占比更高；与鲁兹臂形草、俯仰臂形草及无性系1相比，铺地臂形草、95号与97号无性系的维管束占比更高；中脉区的基本薄壁组织占比，在铺地臂形草、95号无性系与97号无性系中更高。综上可得出结论：鲁兹臂形草的无性系1，其叶片组织（薄壁组织与韧皮部）具备更高的消化潜力；而铺地臂形草与俯仰臂形草的木质部与厚壁组织占比较高，会降低其作为饲草的品质。